Entity Central Index Key Business combination recognized identifiable assets acquired and liabilities assumed operating leases right of use assets. Business combination recognized identifiable assets acquired and liabilities assumed current liabilities accrued expenses and other liabilities. Business combination recognized identifiable assets acquired and liabilities assumed operating leases short-term lease liabilities. Business combination recognized identifiable assets acquired and liabilities assumed income tax payable. Business combination recognized identifiable assets acquired and liabilities assumed operating leases long-term lease liabilities. Long-term employee incentives. Adjusted EBITDA attributable to parent. Adjusted EBITDA attributable to noncontrolling interests. Sale leaseback transaction amortization of deferred gain. Transaction related costs. Other reconciliation from net income to adjusted EBITDA. Cover [Abstract] Document Type Document Type Amendment Flag Amendment Flag Document Period End Date Document Period End Date Document Fiscal Year Focus Document Fiscal Year Focus Document Fiscal Period Focus Document Fiscal Period Focus Trading Symbol Trading Symbol Entity Registrant Name Entity Registrant Name Entity Central Index Key Current Fiscal Year End Date Current Fiscal Year End Date Entity Current Reporting Status Entity Current Reporting Status Entity Shell Company Entity Shell Company Entity Filer Category Entity Filer Category Entity Small Business Entity Small Business Entity Emerging Growth Company Entity Emerging Growth Company Entity Common Stock, Shares Outstanding Entity Common Stock Shares Outstanding Entity File Number Entity File Number Entity Tax Identification Number Entity Tax Identification Number Entity Address, Address Line One Entity Address Address Line1 Entity Address, City or Town Entity Address City Or Town Entity Address, State or Province Entity Address State Or Province Entity Address, Postal Zip Code Entity Address Postal Zip Code City Area Code City Area Code Local Phone Number Local Phone Number Title of 12(b) Security Security12b Title Security Exchange Name Security Exchange Name Document Quarterly Report Document Quarterly Report Document Transition Report Document Transition Report Entity Incorporation, State or Country Code Entity Incorporation State Country Code Entity Interactive Data Current Entity Interactive Data Current Accrued expenses and other current liabilities. Statement Of Financial Position [Abstract] Assets Assets [Abstract] Current assets: Assets Current [Abstract] Cash and cash equivalents (including $73,794 and $55,054 Cash of consolidated joint ventures) Cash And Cash Equivalents At Carrying Value Restricted cash and investments Restricted Cash And Investments Current Accounts receivable, net (including $180,325 and $164,460 Accounts receivable of consolidated joint ventures, net) Accounts Receivable Net Current Contract assets (including $21,270 and $26,542 Contract assets of consolidated joint ventures) Contract With Customer Asset Net Current Prepaid expenses and other current assets (including $11,837 and $8,149 Prepaid expenses and other current assets of consolidated joint ventures) Prepaid Expense And Other Assets Current Total current assets Assets Current Property and equipment, net (including $2,561 and $3,171 Property and equipment of consolidated joint ventures, net) Property Plant And Equipment Net Right of use assets, operating leases Operating Lease Right Of Use Asset Goodwill Goodwill Investments in and advances to unconsolidated joint ventures Investments In Affiliates Subsidiaries Associates And Joint Ventures Intangible assets, net Intangible Assets Net Excluding Goodwill Deferred tax assets Deferred Income Tax Assets Net Other noncurrent assets Other Assets Noncurrent Total assets Assets Liabilities and Shareholders' Equity (Deficit) Liabilities And Stockholders Equity [Abstract] Current liabilities: Liabilities Current [Abstract] Accounts payable (including $87,914 and $90,692 Accounts payable of consolidated joint ventures) Accounts Payable Current Accrued expenses and other current liabilities (including $73,209 and $63,880 Accrued expenses and other current liabilities of consolidated joint ventures) Accrued Expenses And Other Current Liabilities Contract liabilities (including $38,706 and $43,324 Contract liabilities of consolidated joint ventures) Contract With Customer Liability Current Short-term lease liabilities, operating leases Operating Lease Liability Current Income taxes payable Taxes Payable Current Total current liabilities Liabilities Current Long-term employee incentives Long Term Employee Incentives Deferred gain resulting from sale-leaseback transactions Sale Leaseback Transaction Deferred Gain Net Long-term debt Long Term Debt Long-term lease liabilities, operating leases Operating Lease Liability Noncurrent Deferred tax liabilities Deferred Income Tax Liabilities Net Other long-term liabilities Other Liabilities Noncurrent Total liabilities Liabilities Commitments and contingencies (Note 13) Commitments And Contingencies Redeemable common stock held by Employee Stock Ownership Plan (ESOP), $1 par value; 78,172,809 and 78,138,602 shares outstanding, recorded at redemption value Temporary Equity Carrying Amount Attributable To Parent Shareholders' equity (deficit): Stockholders Equity Including Portion Attributable To Noncontrolling Interest [Abstract] Common stock, $1 par value; authorized 1,000,000,000 shares; 125,097,684 and 146,393,959 shares issued; 0 and 21,296,275 shares outstanding Common Stock Value Treasury stock, 46,918,140 and 46,959,082 shares at cost Treasury Stock Value Additional paid-in capital Additional Paid In Capital Common Stock Retained earnings (accumulated deficit) Retained Earnings Accumulated Deficit Accumulated other comprehensive loss Accumulated Other Comprehensive Income Loss Net Of Tax Total Parsons Corporation shareholders' equity (deficit) Stockholders Equity Noncontrolling interests Minority Interest Total shareholders' equity (deficit) Stockholders Equity Including Portion Attributable To Noncontrolling Interest Total liabilities, redeemable common stock and shareholders' equity (deficit) Liabilities And Stockholders Equity Statement [Table] Statement [Table] Related Party Related Party Transactions By Related Party [Axis] Related Party Related Party [Domain] Consolidated joint ventures. Consolidated Joint Ventures Consolidated Joint Ventures [Member] Statement [Line Items] Statement [Line Items] Cash and cash equivalents Accounts receivable, net Contract assets Prepaid expenses and other current assets Property and equipment, net Accounts payable Accrued expenses and other current liabilities Contract liabilities Temporary equity, par value Temporary Equity Par Or Stated Value Per Share Temporary equity, shares outstanding Temporary Equity Shares Outstanding Common stock, par value Common Stock Par Or Stated Value Per Share Common stock, authorized Common Stock Shares Authorized Common stock, issued Common Stock Shares Issued Common stock, outstanding Common Stock Shares Outstanding Treasury stock, shares Treasury Stock Shares Gain (loss) on long-term contract. Other income (expense). Income Statement [Abstract] Revenues Revenue From Contract With Customer Excluding Assessed Tax Direct costs of contracts Cost Of Goods And Services Sold Equity in earnings of unconsolidated joint ventures Income Loss From Equity Method Investments Indirect, general and administrative expenses General And Administrative Expense Operating income Operating Income Loss Interest income Investment Income Interest Interest expense Interest Expense Other income (expense), net Other Nonoperating Income Expense Gain associated with claim on long-term contract Gain Loss On Long Term Contract Total other income (expense) Other Income Expense Income before income tax provision Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest Income tax benefit (provision) Income Tax Expense Benefit Net income including noncontrolling interests Profit Loss Net income attributable to noncontrolling interests Net Income Loss Attributable To Noncontrolling Interest Net income attributable to Parsons Corporation Net Income Loss Earnings per share: Earnings Per Share [Abstract] Basic and diluted Earnings Per Share Basic And Diluted Statement Of Income And Comprehensive Income [Abstract] Net income including noncontrolling interests Other comprehensive income (loss), net of tax Other Comprehensive Income Loss Net Of Tax Period Increase Decrease [Abstract] Foreign currency translation adjustment, net of tax Other Comprehensive Income Loss Foreign Currency Transaction And Translation Adjustment Net Of Tax Pension adjustments, net of tax Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Adjustment Net Of Tax Comprehensive income including noncontrolling interests, net of tax Comprehensive Income Net Of Tax Including Portion Attributable To Noncontrolling Interest Comprehensive income attributable to noncontrolling interests, net of tax Comprehensive Income Net Of Tax Attributable To Noncontrolling Interest Comprehensive income attributable to Parsons Corporation, net of tax Comprehensive Income Net Of Tax Amortization of deferred gains. Increase (decrease) in prepaid expense and current assets. Increase (decrease) in accrued expenses and other current liabilities. Increase (decrease) in billings in excess of costs. Increase (decrease) in provision for contract losses. Payments for purchase of treasury stock. Statement Of Cash Flows [Abstract] Cash flows from operating activities: Net Cash Provided By Used In Operating Activities [Abstract] Adjustments to reconcile net income to net cash used in operating activities Adjustments To Reconcile Net Income Loss To Cash Provided By Used In Operating Activities [Abstract] Depreciation and amortization Depreciation And Amortization Amortization of deferred gain Amortization Of Deferred Gains Amortization of debt issue costs Amortization Of Financing Costs Gain associated with claim on long-term contract Gain Loss Related To Litigation Settlement Loss on disposal of property and equipment Gain Loss On Sale Of Property Plant Equipment Provision for doubtful accounts Provision For Doubtful Accounts Deferred taxes Deferred Income Tax Expense Benefit Foreign currency transaction gains and losses Foreign Currency Transaction Gain Loss Before Tax Equity in earnings of unconsolidated joint ventures Return on investments in unconsolidated joint ventures Equity Method Investment Dividends Or Distributions Stock-based compensation Share Based Compensation Contributions of treasury stock Other Postretirement Benefits Expense Reversal Of Expense Noncash Changes in assets and liabilities, net of acquisitions and newly consolidated joint ventures: Increase Decrease In Operating Capital [Abstract] Accounts receivable Increase Decrease In Accounts Receivable Contract assets Increase Decrease In Contract With Customer Asset Prepaid expenses and current assets Increase Decrease In Prepaid Expense And Current Assets Accounts payable Increase Decrease In Accounts Payable Accrued expenses and other current liabilities Increase Decrease In Accrued Expenses And Other Current Liabilities Billings in excess of costs Increase Decrease In Billings In Excess Of Costs Contract liabilities Increase Decrease In Contract With Customer Liability Provision for contract losses Increase Decrease In Provision For Contract Losses Income taxes Increase Decrease In Income Taxes Other long-term liabilities Increase Decrease In Other Noncurrent Liabilities Net cash provided by operating activities Net Cash Provided By Used In Operating Activities Cash flows from investing activities: Net Cash Provided By Used In Investing Activities [Abstract] Capital expenditures Payments To Acquire Productive Assets Proceeds from sale of property and equipment Proceeds From Sale Of Property Plant And Equipment Payments for acquisitions, net of cash acquired Payments To Acquire Businesses Net Of Cash Acquired Investments in unconsolidated joint ventures Payments To Acquire Interest In Joint Venture Return of investments in unconsolidated joint ventures Proceeds From Equity Method Investment Dividends Or Distributions Return Of Capital Net cash used in investing activities Net Cash Provided By Used In Investing Activities Cash flows from financing activities: Net Cash Provided By Used In Financing Activities [Abstract] Proceeds from borrowings Proceeds From Lines Of Credit Repayments of borrowings Repayments Of Lines Of Credit Payments for debt costs and credit agreement Payments Of Debt Issuance Costs Contributions by noncontrolling interests Proceeds From Minority Shareholders Distributions to noncontrolling interests Payments To Minority Shareholders Purchase of treasury stock Payments For Purchase Of Treasury Stock IPO proceeds, net Proceeds From Issuance Initial Public Offering Dividend paid Payments Of Dividends Net cash provided by financing activities Net Cash Provided By Used In Financing Activities Effect of exchange rate changes Effect Of Exchange Rate On Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Net decrease in cash, cash equivalents, and restricted cash Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Period Increase Decrease Including Exchange Rate Effect Cash, cash equivalents and restricted cash: Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Period Increase Decrease Excluding Exchange Rate Effect [Abstract] Cash, cash equivalents and restricted cash, beginning of period Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Cash, cash equivalents and restricted cash, end of period Minority interest increase (decrease) from contributions to noncontrolling interest holders. Accretion of redeemable common stock. Temporary equity purchase of treasury stock. Statement Of Stockholders Equity [Abstract] Retained Earnings (Accumulated Deficit) Statement Equity Components [Axis] Equity Component Equity Component [Domain] Redeemable common stock. Redeemable Common Stock Redeemable Common Stock [Member] Common Stock Common Stock [Member] Treasury Stock Treasury Stock [Member] Additional Paid-In Capital Additional Paid In Capital [Member] Retained Earnings (Accumulated Deficit) Retained Earnings [Member] Accumulated Other Comprehensive Income (Loss) Accumulated Other Comprehensive Income [Member] Total Parsons Deficit Parent [Member] Noncontrolling Interest Noncontrolling Interest [Member] Adjustments for New Accounting Pronouncements Adjustments For New Accounting Pronouncements [Axis] Type of Adoption Type Of Adoption [Member] ASC 842 Accounting Standards Update201602 [Member] ASC 606 Accounting Standards Update201409 [Member] Sale of Stock Subsidiary Sale Of Stock [Axis] Sale of Stock Sale Of Stock Name Of Transaction [Domain] IPO I P O [Member] Beginning balance Beginning balance, Temporary Equity Comprehensive income Comprehensive Income Net Of Tax Including Portion Attributable To Noncontrolling Interest [Abstract] Net income Foreign currency translation gain (loss), net Other Comprehensive Income Foreign Currency Transaction And Translation Gain Loss Arising During Period Net Of Tax Pension adjustments, net Adjustment due to adoption of ASC New Accounting Pronouncement Or Change In Accounting Principle Effect Of Adoption Quantification Purchase of treasury stock Treasury Stock Value Acquired Cost Method Contributions Minority Interest Increase Decrease From Contributions To Noncontrolling Interest Holders Distributions Minority Interest Decrease From Distributions To Noncontrolling Interest Holders Dividend paid Dividends Stock-based compensation Adjustments To Additional Paid In Capital Sharebased Compensation Requisite Service Period Recognition Value Conversion of S-Corp to C-Corp Stock Issued During Period Value Conversion Of Units Temporary equity stock issued during period value conversion of units. Temporary equity, Conversion of S-Corp to C-Corp Temporary Equity Stock Issued During Period Value Conversion Of Units IPO proceeds, net Stock Issued During Period Value New Issues Accretion of redeemable common stock Accretion Of Redeemable Common Stock Temporary equity, Accretion of redeemable common stock Temporary Equity Accretion To Redemption Value Ending Balance Ending Balance, Temporary Equity Temporary equity, Purchase of treasury stock Temporary Equity Purchase Of Treasury Stock ESOP shares at redemption value Stock Redeemed Or Called During Period Value Temporary stock redeemed or called during period value. Temporary equity, ESOP shares at redemption value Temporary Stock Redeemed Or Called During Period Value Description of operations disclosure. Description Of Operations Disclosure [Abstract] Description of Operations Nature Of Operations Organization Consolidation And Presentation Of Financial Statements [Abstract] Basis of Presentation and Principles of Consolidation Organization Consolidation And Presentation Of Financial Statements Disclosure [Text Block] Accounting Policies [Abstract] Recently Adopted Accounting Pronouncements New Accounting Pronouncements And Changes In Accounting Principles [Text Block] Business Combinations [Abstract] Acquisitions Business Combination Disclosure [Text Block] Revenue From Contract With Customer [Abstract] Contracts with Customers Revenue From Contract With Customer [Text Block] Leases [Abstract] Leases Leases Of Lessee Disclosure [Text Block] Goodwill And Intangible Assets Disclosure [Abstract] Goodwill Goodwill Disclosure [Text Block] Intangible Assets Intangible Assets Disclosure [Text Block] Property Plant And Equipment [Abstract] Property and Equipment, Net Property Plant And Equipment Disclosure [Text Block] Sale-Leasebacks Sale Leaseback Transaction Disclosure [Text Block] Debt Disclosure [Abstract] Debt and Credit Facilities Debt Disclosure [Text Block] Income Tax Disclosure [Abstract] Income Taxes Income Tax Disclosure [Text Block] Commitments And Contingencies Disclosure [Abstract] Commitments and Contingencies Commitments And Contingencies Disclosure [Text Block] Compensation And Retirement Disclosure [Abstract] Retirement and Other Benefit Plans Compensation And Employee Benefit Plans [Text Block] Equity Method Investments And Joint Ventures [Abstract] Investments in and Advances to Joint Ventures Equity Method Investments Disclosure [Text Block] Related Party Transactions [Abstract] Related Party Transactions Related Party Transactions Disclosure [Text Block] Fair Value Disclosures [Abstract] Fair Value of Financial Instruments Fair Value Disclosures [Text Block] Earnings Per Share Earnings Per Share [Text Block] Segment Reporting [Abstract] Segment Information Segment Reporting Disclosure [Text Block] Subsequent Events [Abstract] Subsequent Events Subsequent Events [Text Block] Accumulated Deficit Stockholders Equity Policy [Text Block] Fiscal Periods Fiscal Period Use of Estimates Use Of Estimates Inventory Inventory Policy [Text Block] Redeemable common stock policy. Redeemable Common Stock Redeemable Common Stock Policy Policy [Text Block] Leases Lessee Leases Policy [Text Block] Business Acquisition Business Acquisition [Axis] Business Acquisition, Acquiree Business Acquisition Acquiree [Domain] Polaris Alpha. Polaris Alpha Polaris Alpha [Member] OGSystems. OGSystems O G Systems [Member] QRC Technologies. QRC Technologies Q R C Technologies [Member] Summary of Estimated Fair Values of Assets Acquired and Liabilities Assumed on Preliminary Purchase Price Allocation Schedule Of Recognized Identified Assets Acquired And Liabilities Assumed Table [Text Block] Schedule of Intangible Assets Value on Purchase Price Schedule Of Finite Lived Intangible Assets Acquired As Part Of Business Combination [Text Block] Schedule of Supplemental Pro Forma Information Business Acquisition Pro Forma Information [Text Block] Summary of Disaggregation of Revenue Disaggregation Of Revenue Table [Text Block] Summary of Contract Assets and Contract Liabilities Contract With Customer Asset And Liability Table [Text Block] Schedule of change in contract assets and contract liabilities. Summary of Changes in Contract Assets and Contract Liabilities Schedule Of Change In Contract Assets And Contract Liabilities Table [Text Block] Summary of Accounts Receivable, Net Schedule Of Accounts Notes Loans And Financing Receivable [Text Block] Summary of Remaining Unsatisfied Performance Obligations Expect to Satisfy Revenue Remaining Performance Obligation Expected Timing Of Satisfaction Table [Text Block] Summary of Lease Costs Lease Cost Table [Text Block] Schedule of cash flow information related to leases. Schedule of Supplemental Cash Flow Information Related to Leases Schedule Of Cash Flow Information Related To Leases Table [Text Block] Schedule of balance sheet information related to leases. Schedule of Supplemental Balance Sheet and Other Information Related to Leases Schedule Of Balance Sheet Information Related To Leases Table [Text Block] Schedule of maturities of operating and finance lease liabilities. Schedule of Maturity Analysis of Future Undiscounted Cash Flows Schedule Of Maturities Of Operating And Finance Lease Liabilities Table [Text Block] Summary of Changes in Carrying Value of Goodwill by Reporting Segment Schedule Of Goodwill [Text Block] Schedule of Gross Amount and Accumulated Amortization of Intangible Assets Schedule Of Acquired Finite Lived Intangible Assets By Major Class [Text Block] Schedule of Estimated Amortization Expense Scheduleof Finite Lived Intangible Assets Future Amortization Expense Table [Text Block] Schedule of Property and equipment, net Property Plant And Equipment [Text Block] Schedule of Long Term Debt Schedule Of Debt Table [Text Block] Schedule of aggregate amount debt repayable. Schedule of Aggregate Amount Debt Repayable Schedule Of Aggregate Amount Debt Repayable Table [Text Block] Schedule of financial information of consolidated joint ventures. Summary of Financial Information for Consolidated Joint Ventures Schedule Of Financial Information Of Consolidated Joint Ventures Table [Text Block] Summary of Financial Information for Unconsolidated Joint Ventures Equity Method Investments [Text Block] Schedule of consolidated balance sheet related to unconsolidated joint ventures. Schedule of Consolidated Balance Sheet Related to Services Provided to Unconsolidated Joint Ventures Schedule Of Consolidated Balance Sheet Related To Unconsolidated Joint Ventures Table [Text Block] Summary of fair value assets associated with pension plan. Summary of Fair Value Assets Associated with Pension Plan Summary Of Fair Value Assets Associated With Pension Plan Table [Text Block] Schedule of fair value of redeemable common stock associated employee stock ownership plan. Schedule of Fair Value of Redeemable Common Stock Associated Employee Stock Ownership Plan Schedule Of Fair Value Of Redeemable Common Stock Associated Employee Stock Ownership Plan Table [Text Block] Schedule of Reconciliation Fair Value Measurements Using Significant Unobservable Inputs Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Text Block] Schedule of Weighted Average Number of Shares Used To Compute Basic and Diluted EPS Schedule Of Weighted Average Number Of Shares Table [Text Block] Summary of Business Segment Information Schedule Of Segment Reporting Information By Segment [Text Block] Summary of Adjusted EBITDA Business Segment Information Reconciliation Of Operating Profit Loss From Segments To Consolidated [Text Block] Summary of revenues and property and equipment, net by geographic area. Summary of Revenues and Property and Equipment, Net by Geographic Area Summary Of Revenues And Property And Equipment Net By Geographic Area Table [Text Block] Summary of Revenues by Business Lines Schedule Of Entity Wide Information Revenue From External Customers By Products And Services [Text Block] Purchase of additional shares upon exercise of options. Underwriting discount per share. Funds to dividends through public offering. Repayment on term loan through public offering. Description of operations disclosure. Description of operations disclosure. Description Of Operations Disclosure [Table] Description Of Operations Disclosure [Table] IPO Underwriters Over Allotment Option [Member] Description Of Operations Disclosure [Line Items] Description Of Operations Disclosure [Line Items] Common stock shares sold Stock Issued During Period Shares New Issues Common stock sold per share Sale Of Stock Price Per Share Purchase of additional shares upon exercise of options Purchase Of Additional Shares Upon Exercise Of Options Share price Share Price Underwriting discount per share Underwriting Discount Per Share Proceeds from IPO Funds to dividend through public offering Funds To Dividends Through Public Offering Repayment on term loan through public offering Repayment On Term Loan Through Public Offering Common stock dividend ratio. Dividend payable payment date. Common stock dividend ratio Common Stock Dividend Ratio Dividends payment, date Dividend Payable Payment Date New Accounting Pronouncements Or Change In Accounting Principle [Table] New Accounting Pronouncements Or Change In Accounting Principle [Table] Initial Application Period Cumulative Effect Transition Initial Application Period Cumulative Effect Transition [Axis] Initial Application Period Cumulative Effect Transition Initial Application Period Cumulative Effect Transition [Domain] Difference between Revenue Guidance in Effect before and after Topic 606 Difference Between Revenue Guidance In Effect Before And After Topic606 [Member] New Accounting Pronouncements Or Change In Accounting Principle [Line Items] New Accounting Pronouncements Or Change In Accounting Principle [Line Items] Retained earnings Schedule Of Business Acquisitions By Acquisition [Table] Schedule Of Business Acquisitions By Acquisition [Table] Income Statement Location Income Statement Location [Axis] Income Statement Location Income Statement Location [Domain] Indirect, General and Administrative Expense. Indirect, General and Administrative Expense Indirect General And Administrative Expense [Member] Short-term Debt, Type Short Term Debt Type [Axis] Short-term Debt, Type Short Term Debt Type [Domain] Term loan. Term Loan Term Loan [Member] Credit Facility Credit Facility [Axis] Credit Facility Credit Facility [Domain] Revolving Credit Facility Revolving Credit Facility [Member] Business Acquisition [Line Items] Business Acquisition [Line Items] Percentage of ownership interest acquired Business Acquisition Percentage Of Voting Interests Acquired Cash paid to acquire Payments To Acquire Businesses Gross Borrowed under credit agreement to partially fund the acquisition Business Combination Consideration Transferred Liabilities Incurred Acquisition related expenses Business Combination Acquisition Related Costs Cash and cash equivalents Business Combination Recognized Identifiable Assets Acquired And Liabilities Assumed Cash And Equivalents Accounts receivable Business Combination Recognized Identifiable Assets Acquired And Liabilities Assumed Current Assets Receivables Contract assets Prepaid expenses and other current assets Business Combination Recognized Identifiable Assets Acquired And Liabilities Assumed Current Assets Prepaid Expense And Other Assets Property and equipment Business Combination Recognized Identifiable Assets Acquired And Liabilities Assumed Property Plant And Equipment Right of use assets, operating leases Business Combination Recognized Identifiable Assets Acquired And Liabilities Assumed Operating Leases Right Of Use Assets Intangible assets Business Combination Recognized Identifiable Assets Acquired And Liabilities Assumed Intangible Assets Other Than Goodwill Deferred tax assets Business Combination Recognized Identifiable Assets Acquired And Liabilities Assumed Deferred Tax Assets Other noncurrent assets Business Combination Recognized Identifiable Assets Acquired And Liabilities Assumed Other Noncurrent Assets Accounts payable Business Combination Recognized Identifiable Assets Acquired And Liabilities Assumed Current Liabilities Accounts Payable Accrued expenses and other current liabilities Business Combination Recognized Identifiable Assets Acquired And Liabilities Assumed Current Liabilities Accrued Expenses And Other Liabilities Contract liabilities Short-term lease liabilities, operating leases Business Combination Recognized Identifiable Assets Acquired And Liabilities Assumed Operating Leases Short Term Lease Liabilities Income tax payable Business Combination Recognized Identifiable Assets Acquired And Liabilities Assumed Income Tax Payable Deferred tax liabilities Business Combination Recognized Identifiable Assets Acquired And Liabilities Assumed Deferred Tax Liabilities Noncurrent Long-term lease liabilities, operating leases Business Combination Recognized Identifiable Assets Acquired And Liabilities Assumed Operating Leases Long Term Lease Liabilities Other long-term liabilities Business Combination Recognized Identifiable Assets Acquired And Liabilities Assumed Noncurrent Liabilities Other Net assets acquired Business Combination Recognized Identifiable Assets Acquired And Liabilities Assumed Net Finite Lived Intangible Assets Acquired As Part Of Business Combination [Table] Finite Lived Intangible Assets Acquired As Part Of Business Combination [Table] Finite-Lived Intangible Assets by Major Class Finite Lived Intangible Assets By Major Class [Axis] Finite-Lived Intangible Assets, Major Class Name Finite Lived Intangible Assets Major Class Name [Domain] Developed Technology Developed Technology Rights [Member] Customer Relationships Customer Relationships [Member] Backlog Order Or Production Backlog [Member] Trade Name Trade Names [Member] Leases Lease Agreements [Member] Non compete Agreements Noncompete Agreements [Member] Statistical Measurement Range [Axis] Statistical Measurement Range [Member] Minimum Minimum [Member] Maximum Maximum [Member] Acquired Finite Lived Intangible Assets [Line Items] Acquired Finite Lived Intangible Assets [Line Items] Gross Carrying Amount Finitelived Intangible Assets Acquired1 Amortization Period (in years) Acquired Finite Lived Intangible Assets Weighted Average Useful Life Amortization of intangible assets Amortization Of Intangible Assets Goodwill deductible for tax purposes Business Acquisition Purchase Price Allocation Goodwill Expected Tax Deductible Amount Business acquisition, pro forma net income (loss), including portion attributable to noncontrolling interest. Pro forma revenue Business Acquisitions Pro Forma Revenue Pro forma net income including noncontrolling interests Business Acquisition Pro Forma Net Income Loss Including Portion Attributable To Noncontrolling Interest Disaggregation Of Revenue [Table] Disaggregation Of Revenue [Table] Contract with Customer, Basis of Pricing Contract With Customer Basis Of Pricing [Axis] Contract with Customer, Basis of Pricing Contract With Customer Basis Of Pricing [Domain] Fixed-Price Fixed Price Contract [Member] Time-and-Materials Time And Materials Contract [Member] Cost plus. Cost-Plus Cost Plus [Member] Disaggregation Of Revenue [Line Items] Disaggregation Of Revenue [Line Items] Contract with customer asset and liabilities net. Change in contract with customer assets and liabilities net. Change in contract with customer assets. Change in contract with customer liability. Contract assets Contract With Customer Asset Net Contract liabilities Contract With Customer Liability Net contract assets (liabilities) Contract With Customer Asset Liability Net Change in contract assets Change In Contract With Customer Assets Change in contract liabilities Change In Contract With Customer Liability Change in contract assets and liabilities Change In Contract With Customer Assets And Liabilities Net Contract with customer asset cumulative catchup adjustment to revenue change in measure of progress percent. Contract with customer liability cumulative catchup adjustment to revenue change in measure of progress percent. Contract with customer asset cumulative catchup adjustment to revenue change in measure of progress percent. Percentage change in contract assets Contract With Customer Asset Cumulative Catchup Adjustment To Revenue Change In Measure Of Progress Percent Percentage change in contract liabilities Contract With Customer Liability Cumulative Catchup Adjustment To Revenue Change In Measure Of Progress Percent Percentage change in contract assets and liabilities Contract With Customer Asset Liability Cumulative Catchup Adjustment To Revenue Change In Measure Of Progress Percent Contract retentions Contract Receivable Retainage Contract retentions, not expected to be paid in next 12 months Contract Receivable Retainage Due After One Year Contract assets, unapproved change orders, claims, and requests Contracts Receivable Claims And Uncertain Amounts Revenue recognized included contract liability Contract With Customer Liability Revenue Recognized Reversal of provision for contract losses. Acquired contract assets Contract With Customer Asset Increase Decrease For Contract Acquired In Business Combination Acquired contract liabilities Contract With Customer Liability Increase Decrease For Contract Acquired In Business Combination Change in the estimate of variable consideration Contract With Customer Liability Cumulative Catch Up Adjustment To Revenue Change In Estimate Of Transaction Price Reversal of provision for contract losses Reversal Of Provision For Contract Losses Increase in revenue due to reversal of provision for contract losses. Reversal for provision for contract losses Increase in revenue recorded in other income Increase In Revenue Due To Reversal Of Provision For Contract Losses Impairment of contract assets Capitalized Contract Cost Impairment Loss Contract with customer adjustment to revenue impact of changes in estimated claims or incentives over threshold. Impact of changes in estimated claims or incentives on revenue Contract With Customer Adjustment To Revenue Impact Of Changes In Estimated Claims Or Incentives Over Threshold Increase in revenue due to Impact of changes in estimated claims or incentives Contract With Customer Liability Cumulative Catch Up Adjustment To Revenue Change In Measure Of Progress Billed receivables current. Billed Billed Receivables Current Unbilled Unbilled Receivables Current Total accounts receivable, gross Accounts Receivable Gross Current Allowance for doubtful accounts Allowance For Doubtful Accounts Receivable Current Total accounts receivable, net Remaining unsatisfied performance obligations Revenue Remaining Performance Obligation Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Table] Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Table] Segments Statement Business Segments [Axis] Segments Segment [Domain] Federal Solution Segment. Federal Solution Segment Federal Solution Segment [Member] Critical Infrastructure Segment. Critical Infrastructure Critical Infrastructure Segment [Member] Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date Revenue Remaining Performance Obligation Expected Timing Of Satisfaction Start Date [Axis] Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items] Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items] Revenue, remaining performance obligation, expected timing of satisfaction, period Revenue Remaining Performance Obligation Expected Timing Of Satisfaction Period1 Lessee Lease Description [Table] Lessee Lease Description [Table] Accounting Standards Update 2016-02 Valuation Allowance by Deferred Tax Asset Valuation Allowance By Deferred Tax Asset [Axis] Deferred Tax Asset Deferred Tax Asset [Domain] Net deferred tax asset. Net Deferred Tax Asset Net Deferred Tax Asset [Member] Deferred tax asset. Deferred Tax Asset Deferred Tax Asset [Member] Minimum [Member] Maximum [Member] Lessee Lease Description [Line Items] Lessee Lease Description [Line Items] Cumulative effect adjustment to retained earnings Lessee lease term of contract. Lessee lease option to extend. Lessee lease option to terminate. Finance lease right of use assets accumulated depreciation. Lessee lease existence of option to extend. Lessee lease existence of option to terminate. Lease term of contract Lessee Lease Term Of Contract Lease option to extend Lessee Lease Option To Extend Lease existence of option to extend Lessee Lease Existence Of Option To Extend Lease option to terminate Lessee Lease Option To Terminate Lease existence of option to terminate Lessee Lease Existence Of Option To Terminate Finance lease right-of-use asset Finance Lease Right Of Use Asset Finance lease right of use assets accumulated depreciation Finance Lease Right Of Use Assets Accumulated Depreciation Operating lease cost Operating Lease Cost Short-term lease cost Short Term Lease Cost Amortization of right-of-use assets Finance Lease Right Of Use Asset Amortization Interest on lease liabilities Finance Lease Interest Expense Sublease income Sublease Income Total lease cost Lease Cost Operating cash flows for operating leases Operating Lease Payments Operating cash flows for financing activities Finance Lease Principal Payments Right-of-use assets obtained in exchange for new operating lease liabilities Right Of Use Asset Obtained In Exchange For Operating Lease Liability Right-of-use assets obtained in exchange for new finance lease liabilities Right Of Use Asset Obtained In Exchange For Finance Lease Liability Operating lease. Lease liabilities. Finance leases. Finance leases other assets noncurrent. Finance lease liabilities. Weighted average remaining lease term. Weighted average discount rate. Operating Leases: Operating Leases [Abstract] Lease liabilities: Lease Liabilities [Abstract] Total operating lease liabilities Operating Lease Liability Finance Leases: Finance Leases [Abstract] Other noncurrent assets Finance Leases Other Assets Noncurrent Lease liabilities: Finance Lease Liabilities [Abstract] Accrued expenses and other current liabilities Finance Lease Liability Current Finance Lease, Liability, Current, Statement of Financial Position [Extensible List] Finance Lease Liability Current Statement Of Financial Position Extensible List Other long-term liabilities Finance Lease Liability Noncurrent Finance Lease, Liability, Noncurrent, Statement of Financial Position [Extensible List] Finance Lease Liability Noncurrent Statement Of Financial Position Extensible List Total finance lease liabilities Finance Lease Liability Weighted Average Remaining Lease Term: Weighted Average Remaining Lease Term [Abstract] Operating leases Operating Lease Weighted Average Remaining Lease Term1 Finance leases Finance Lease Weighted Average Remaining Lease Term1 Weighted Average Discount Rate: Weighted Average Discount Rate [Abstract] Operating leases Operating Lease Weighted Average Discount Rate Percent Finance leases Finance Lease Weighted Average Discount Rate Percent Operating lease not yet commenced expense. Operating lease not yet commenced expense Operating Lease Not Yet Commenced Expense Operating lease not yet commenced term of contract Lessee Operating Lease Lease Not Yet Commenced Term Of Contract1 Operating Leases Operating Lease Liabilities Payments Due [Abstract] 2019 Lessee Operating Lease Liability Payments Remainder Of Fiscal Year 2020 Lessee Operating Lease Liability Payments Due Year Two 2021 Lessee Operating Lease Liability Payments Due Year Three 2022 Lessee Operating Lease Liability Payments Due Year Four 2023 Lessee Operating Lease Liability Payments Due Year Five Thereafter Lessee Operating Lease Liability Payments Due After Year Five Total lease payments Lessee Operating Lease Liability Payments Due Less: imputed interest Lessee Operating Lease Liability Undiscounted Excess Amount Total present value of lease liabilities Finance Leases Finance Lease Liabilities Payments Due [Abstract] 2019 Finance Lease Liability Payments Remainder Of Fiscal Year 2020 Finance Lease Liability Payments Due Year Two 2021 Finance Lease Liability Payments Due Year Three 2022 Finance Lease Liability Payments Due Year Four 2023 Finance Lease Liability Payments Due Year Five Thereafter Finance Lease Liability Payments Due After Year Five Total lease payments Finance Lease Liability Payments Due Less: imputed interest Finance Lease Liability Undiscounted Excess Amount Total present value of lease liabilities Operating leases future minimum payments receivable in six years. Minimum rental commitments on operating leases, current Operating Leases Future Minimum Payments Receivable Current Minimum rental commitments on operating leases, 2019 Operating Leases Future Minimum Payments Receivable In Two Years Minimum rental commitments on operating leases, 2020 Operating Leases Future Minimum Payments Receivable In Three Years Minimum rental commitments on operating leases, 2021 Operating Leases Future Minimum Payments Receivable In Four Years Minimum rental commitments on operating leases, 2022 Operating Leases Future Minimum Payments Receivable In Five Years Minimum rental commitments on operating leases, 2023 Operating Leases Future Minimum Payments Receivable In Six Years Minimum rental commitments on operating leases, thereafter Operating Leases Future Minimum Payments Receivable Thereafter Rent expense Operating Leases Rent Expense Net Schedule Of Goodwill [Table] Schedule Of Goodwill [Table] Federal Solutions Goodwill [Line Items] Goodwill [Line Items] Beginning Balance Acquisitions Goodwill Acquired During Period Foreign Exchange Goodwill Foreign Currency Translation Gain Loss Ending Balance Schedule Of Acquired Finite Lived Intangible Asset By Major Class [Table] Schedule Of Acquired Finite Lived Intangible Asset By Major Class [Table] Other Intangibles Other Intangible Assets [Member] Gross Carrying Amount Finite Lived Intangible Assets Gross Accumulated Amortization Finite Lived Intangible Assets Accumulated Amortization Net Carrying Amount Finite Lived Intangible Assets Net Amortization expense of intangible assets 2019 (remaining) Finite Lived Intangible Assets Amortization Expense Remainder Of Fiscal Year 2020 Finite Lived Intangible Assets Amortization Expense Year Two 2021 Finite Lived Intangible Assets Amortization Expense Year Three 2022 Finite Lived Intangible Assets Amortization Expense Year Four 2023 Finite Lived Intangible Assets Amortization Expense Year Five Thereafter Finite Lived Intangible Assets Amortization Expense After Year Five Schedule Of Property Plant And Equipment [Table] Schedule Of Property Plant And Equipment [Table] Property, Plant and Equipment, Type Property Plant And Equipment By Type [Axis] Property, Plant and Equipment, Type Property Plant And Equipment Type [Domain] Buildings and Leasehold Improvements Building And Building Improvements [Member] Furniture and Equipment Furniture And Fixtures [Member] Computer Systems and Equipment Computer Equipment [Member] Construction equipment. Construction Equipment Construction Equipment [Member] Property Plant And Equipment [Line Items] Property Plant And Equipment [Line Items] Property and equipment, gross Property Plant And Equipment Gross Accumulated depreciation Accumulated Depreciation Depletion And Amortization Property Plant And Equipment Property and equipment, net Useful lives (years) Property Plant And Equipment Useful Life Depreciation expense Depreciation Number of office buildings sold. Sale Leaseback Transaction [Table] Sale Leaseback Transaction [Table] Sale Leaseback Transaction [Line Items] Sale Leaseback Transaction [Line Items] Sale leaseback transaction, description Sale Leaseback Transaction Description Of Asset S Number of sale leaseback transaction associated with sale Number Of Office Buildings Sold Gain recognized to the sale leaseback transaction Sale And Leaseback Transaction Gain Loss Net Amortization of deferred gain Sale Leaseback Transaction Amortization Of Deferred Gain Deferred gain balance recognized New Accounting Pronouncement Or Change In Accounting Principle Cumulative Effect Of Change On Equity Or Net Assets1 Debt Instrument [Table] Debt Instrument [Table] Long-term Debt, Type Longterm Debt Type [Axis] Long-term Debt, Type Longterm Debt Type [Domain] Senior Notes Senior Notes [Member] Debt Instrument [Line Items] Debt Instrument [Line Items] Long-term debt Debt Instrument Carrying Amount Long-Term Debt issuance costs Deferred Finance Costs Noncurrent Net Total long-term Line of credit facility extended date. Credit agreement. Credit Agreement Credit Agreement [Member] Variable Rate Variable Rate [Axis] Variable Rate Variable Rate [Domain] Base Rate Base Rate [Member] LIBOR London Interbank Offered Rate L I B O R [Member] Private Placement Private Placement [Member] Balance Sheet Location Balance Sheet Location [Axis] Balance Sheet Location Balance Sheet Location [Domain] Accrued expenses and other current liabilities. Accrued Expenses and Other Current Liabilities Accrued Expenses And Other Current Liabilities [Member] Fair Value Hierarchy and NAV Fair Value By Fair Value Hierarchy Level [Axis] Fair Value Hierarchy and NAV Fair Value Measurements Fair Value Hierarchy [Domain] Level 2 Fair Value Inputs Level2 [Member] Amended and restated credit agreement date Line Of Credit Facility Initiation Date1 Debt issuance costs incurred Deferred Finance Costs Net Revolving credit facility Line Of Credit Facility Current Borrowing Capacity Increase in revolving credit facility Line Of Credit Facility Maximum Borrowing Capacity Credit agreement extended date Line Of Credit Facility Extended Date Margin interest rate Debt Instrument Basis Spread On Variable Rate1 Interest rate Debt Instrument Interest Rate Stated Percentage Letters of credit outstanding amount Letters Of Credit Outstanding Amount Interest expense Interest Expense Debt Repayment of outstanding balance Repayments Of Debt Series A senior note. Senior Note, Series A Series A Senior Note [Member] Series B senior note. Senior Note, Series B Series B Senior Note [Member] Series C senior note. Senior Note, Series C Series C Senior Note [Member] Series D senior note. Senior Note, Series D Series D Senior Note [Member] Debt Amount Debt Instrument Face Amount Maturity Date Debt Instrument Maturity Date Interest Rates Debt Instrument Interest Rate During Period Interest payments Debt Instrument Periodic Payment Interest payable Interest Payable Current Estimated fair value Long Term Debt Fair Value Effective Corporation tax benefit rate percentage Effective Income Tax Rate Continuing Operations U.S. corporate tax rate Effective Income Tax Rate Reconciliation At Federal Statutory Income Tax Rate Discrete income tax expense (benefit). Expected income tax expense benefit. Deferred tax benefit Revised estimated effects of change in tax status based upon forecasted temporary differences Subsequent Event Effect Of Change In Tax Status Expected Income tax benefit Expected Income Tax Expense Benefit Discrete tax benefit Discrete Income Tax Expense Benefit Deferred tax assets valuation allowance Deferred Tax Assets Valuation Allowance Liability for income taxes associated with uncertain tax positions Liability For Uncertain Tax Positions Current Loss contingency, number of claims. Legal Proceedings [Line Items] Legal Proceedings [Table] Legal Proceedings [Table] Legal Proceedings [Table] Legal Proceedings [Line Items] Legal Proceedings [Line Items] Number of claims outstanding Loss Contingency Number Of Claims Loss contingency damages value Loss Contingency Damages Sought Value Schedule Of Employee Stock Ownership Plan E S O P Disclosures [Table] Schedule Of Employee Stock Ownership Plan E S O P Disclosures [Table] Direct costs of contracts and indirect, general and administrative expense. Direct Costs of Contracts and Indirect, General and Administrative Expense Direct Costs Of Contracts And Indirect General And Administrative Expense [Member] Title of Individual Title Of Individual [Axis] Title of Individual Title Of Individual With Relationship To Entity [Domain] Board of Directors Board Of Directors Chairman [Member] Other Noncurrent Assets Other Noncurrent Assets [Member] Employee Stock Ownership Plan (ESOP) Disclosures [Line Items] Employee Stock Ownership Plan E S O P Disclosures [Line Items] Shares fully vested, Description Share Based Compensation Arrangement By Share Based Payment Award Description Shares fully vested after credited service Share Based Compensation Arrangement By Share Based Payment Award Award Vesting Period1 ESOP contribution expense Employee Stock Ownership Plan E S O P Compensation Expense Common stock dividend date. Initial public offering date. Common stock dividend payment date. Company's stock held by ESOP Employee Stock Ownership Plan E S O P Shares In E S O P ESOP shares aggregate redemption, value Temporary Equity Value Excluding Additional Paid In Capital Dividends payable, amount per share Dividends Payable Amount Per Share Dividends payable Dividends Payable Current And Noncurrent Common stock dividend ratio Common Stock Dividends Shares Common stock dividend date Common Stock Dividend Date Initial public offering date Initial Public Offering Date Common stock dividend payment date Common Stock Dividend Payment Date Dividends declared amount Dividends Common Stock Defined benefit pension plan, net assets position Defined Benefit Plan Assets For Plan Benefits Noncurrent Schedule Of Equity Method Investments [Table] Schedule Of Equity Method Investments [Table] Investment, Name Schedule Of Equity Method Investment Equity Method Investee Name [Axis] Investment, Name Equity Method Investee Name [Domain] Unconsolidated joint ventures. Unconsolidated Joint Ventures Unconsolidated Joint Ventures [Member] Schedule Of Equity Method Investments [Line Items] Schedule Of Equity Method Investments [Line Items] Current assets Noncurrent assets Assets Noncurrent Current liabilities Total joint venture equity Costs Net income attributable to noncontrolling interests Noncurrent liabilities Liabilities Noncurrent Total joint venture equity Equity in earnings of unconsolidated joint ventures Distributions from (contributions to) equity method investment. Net distributions from (contributions to) unconsolidated joint ventures Distributions From Contributions To Equity Method Investment Reimbursable cost incurred. Schedule Of Related Party Transactions By Related Party [Table] Schedule Of Related Party Transactions By Related Party [Table] Unconsolidated joint ventures Majority Owned Subsidiary Unconsolidated [Member] Related Party Transaction [Line Items] Related Party Transaction [Line Items] Revenues Related Party Transaction Other Revenues From Transactions With Related Party Reimbursable cost incurred Reimbursable Cost Incurred Accounts receivable Accounts Receivable Related Parties Current Fair Value By Balance Sheet Grouping [Table] Fair Value By Balance Sheet Grouping [Table] Investment Type Investment Type [Axis] Investments Investment Type Categorization [Member] Mutual Funds Mutual Fund [Member] Fixed Income Fixed Income Funds [Member] Cash and Cash Equivalents Cash And Cash Equivalents [Member] Level 1 Fair Value Inputs Level1 [Member] Level 3 Fair Value Inputs Level3 [Member] Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items] Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items] Assets, fair value disclosure Assets Fair Value Disclosure Redeemable equity common stock fair value. Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Table] Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Table] Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] Redeemable common stock Redeemable Equity Common Stock Fair Value Redeemable equity common stock carrying amount. Shares held by ESOP Employee Stock Ownership Plan E S O P Number Of Allocated Shares Shares held by ESOP, redemption values Redeemable Equity Common Stock Carrying Amount Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Liability Transfers Net [Abstract] Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Table] Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Table] Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items] Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items] Balance at December 31, 2018 Fair Value Measurement With Unobservable Inputs Reconciliations Recurring Basis Liability Value Transfer to Level 1 Fair Value Measurement With Unobservable Inputs Reconciliation Liability Transfers Out Of Level3 Balance at September 30, 2019 Dilutive securities outstanding Antidilutive Securities Excluded From Computation Of Earnings Per Share Amount Basic weighted average number of shares outstanding Weighted Average Number Of Shares Outstanding Basic Dilutive common share equivalents Weighted Average Number Diluted Shares Outstanding Adjustment Diluted weighted average number of shares outstanding Weighted Average Number Of Diluted Shares Outstanding Schedule Of Segment Reporting Information By Segment [Table] Schedule Of Segment Reporting Information By Segment [Table] Geographical Statement Geographical [Axis] Geographical Segment Geographical [Domain] United States UNITED STATES Revenue Sales [Member] Subsegments Subsegments [Axis] Subsegments Subsegments [Domain] Mobility solutions. Mobility Solutions Mobility Solutions [Member] Segment Reporting Information [Line Items] Segment Reporting Information [Line Items] Number of reportable segments Number Of Reportable Segments Total revenue Reconciliation from net income to adjusted EBITDA. Adjusted EBITDA attributable to Parsons Corporation Reconciliation From Net Income To Adjusted E B I T D A [Abstract] Adjusted EBITDA attributable to Parsons Corporation Adjusted E B I T D A Attributable To Parent Adjusted EBITDA attributable to noncontrolling interests Adjusted E B I T D A Attributable To Noncontrolling Interests Depreciation and amortization Interest expense, net Interest Income Expense Net Income tax (expense) benefit Litigation-related gains Amortization of deferred gain resulting from sale-leaseback transactions Equity-based compensation Allocated Share Based Compensation Expense Transaction-related costs Transaction Related Costs Restructuring Restructuring Charges Other Other Reconciliation From Net Income To Adjusted E B I T D A Net income attributable to noncontrolling interests Other nonoperating income. Other Income Other Nonoperating Income [Member] Reversal of accrued liability North America North America [Member] Middle East Middle East [Member] Rest of World Non Us [Member] Property and Equipment, Net Cyber & Intelligence. Cyber & Intelligence Cyber And Intelligence [Member] Defense. Defense Defense [Member] Mission solutions. Mission Solutions Mission Solutions [Member] Engineered systems. Engineered Systems Engineered Systems [Member] Geospatial. Geospatial Geospatial [Member] Connected Communities. Connected Communities Connected Communities [Member] Industrial. Industrial Industrial [Member] Revenue excluding claim settlement. Revenue Excluding Claim Settlement Revenue Excluding Claim Settlement Subsequent Event [Table] Subsequent Event [Table] Employee Stock Ownership Plan (ESOP) Name Employee Stock Ownership Plan E S O P Disclosures By Plan [Axis] Employee Stock Ownership Plan (ESOP), Plan Employee Stock Ownership Plan E S O P Plan [Domain] Employee Stock Ownership Plan. Employee Stock Ownership Plan (“ESOP”) Employee Stock Ownership Plan [Member] Subsequent Event Type Subsequent Event Type [Axis] Subsequent Event Type Subsequent Event Type [Domain] Subsequent Event Subsequent Event [Member] Subsequent Event [Line Items] Subsequent Event [Line Items] Repurchase of common stock, shares Stock Repurchased During Period Shares Repurchase of common stock Stock Repurchased During Period Value