Parsons (PSN) 10-Q 12 Nov 19 2019 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2019	Nov. 04, 2019
Cover [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2019
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q3
Trading Symbol	PSN
Entity Registrant Name	Parsons Corporation
Entity Central Index Key	0000275880
Current Fiscal Year End Date	--12-31
Entity Current Reporting Status	Yes
Entity Shell Company	false
Entity Filer Category	Non-accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Common Stock, Shares Outstanding		99,262,334
Entity File Number	001-07782
Entity Tax Identification Number	95-3232481
Entity Address, Address Line One	5875 Trinity Parkway #300
Entity Address, City or Town	Centreville
Entity Address, State or Province	VA
Entity Address, Postal Zip Code	20120
City Area Code	(703)
Local Phone Number	988-8500
Title of 12(b) Security	Common Stock, $1 par value
Security Exchange Name	NYSE
Document Quarterly Report	true
Document Transition Report	false
Entity Incorporation, State or Country Code	DE
Entity Interactive Data Current	Yes

Consolidated Balance Sheets (Un

Consolidated Balance Sheets (Unaudited) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Current assets:
Cash and cash equivalents (including $73,794 and $55,054 Cash of consolidated joint ventures)	$ 133,870	$ 280,221
Restricted cash and investments	12,592	974
Accounts receivable, net (including $180,325 and $164,460 Accounts receivable of consolidated joint ventures, net)	673,674	623,286
Contract assets (including $21,270 and $26,542 Contract assets of consolidated joint ventures)	583,670	515,319
Prepaid expenses and other current assets (including $11,837 and $8,149 Prepaid expenses and other current assets of consolidated joint ventures)	70,455	69,007
Total current assets	1,474,261	1,488,807
Property and equipment, net (including $2,561 and $3,171 Property and equipment of consolidated joint ventures, net)	109,238	91,849
Right of use assets, operating leases	219,207	0
Goodwill	1,050,077	736,938
Investments in and advances to unconsolidated joint ventures	66,584	63,560
Intangible assets, net	281,157	179,519
Deferred tax assets	111,610	5,680
Other noncurrent assets	50,510	46,225
Total assets	3,362,644	2,612,578
Current liabilities:
Accounts payable (including $87,914 and $90,692 Accounts payable of consolidated joint ventures)	226,563	226,345
Accrued expenses and other current liabilities (including $73,209 and $63,880 Accrued expenses and other current liabilities of consolidated joint ventures)	639,650	559,700
Contract liabilities (including $38,706 and $43,324 Contract liabilities of consolidated joint ventures)	231,032	208,576
Short-term lease liabilities, operating leases	49,074	0
Income taxes payable	9,940	11,540
Total current liabilities	1,156,259	1,006,161
Long-term employee incentives	45,749	41,913
Deferred gain resulting from sale-leaseback transactions	0	46,004
Long-term debt	249,306	429,164
Long-term lease liabilities, operating leases	188,571	0
Deferred tax liabilities	7,337	6,240
Other long-term liabilities	120,971	127,863
Total liabilities	1,768,193	1,657,345
Commitments and contingencies (Note 13)
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	2,577,011	1,876,309
Shareholders' equity (deficit):
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	21,296
Treasury stock, 46,918,140 and 46,959,082 shares at cost	(957,844)	(957,025)
Additional paid-in capital	8,772
Retained earnings (accumulated deficit)	(64,896)	12,445
Accumulated other comprehensive loss	(17,982)	(22,957)
Total Parsons Corporation shareholders' equity (deficit)	(1,010,654)	(967,537)
Noncontrolling interests	28,094	46,461
Total shareholders' equity (deficit)	(982,560)	(921,076)
Total liabilities, redeemable common stock and shareholders' equity (deficit)	$ 3,362,644	$ 2,612,578

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) (Unaudited) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Cash and cash equivalents	$ 133,870	$ 280,221
Accounts receivable, net	673,674	623,286
Contract assets	583,670	515,319
Prepaid expenses and other current assets	70,455	69,007
Property and equipment, net	109,238	91,849
Accounts payable	226,563	226,345
Accrued expenses and other current liabilities	639,650	559,700
Contract liabilities	$ 231,032	$ 208,576
Temporary equity, par value	$ 1	$ 1
Temporary equity, shares outstanding	78,138,602	78,172,809
Common stock, par value	$ 1	$ 1
Common stock, authorized	1,000,000,000	1,000,000,000
Common stock, issued	146,393,959	125,097,684
Common stock, outstanding	21,296,275	0
Treasury stock, shares	46,959,082	46,918,140
Consolidated Joint Ventures
Cash and cash equivalents	$ 55,054	$ 73,794
Accounts receivable, net	164,460	180,325
Contract assets	26,542	21,270
Prepaid expenses and other current assets	8,149	11,837
Property and equipment, net	3,171	2,561
Accounts payable	90,692	87,914
Accrued expenses and other current liabilities	63,880	73,209
Contract liabilities	$ 43,324	$ 38,706

Consolidated Statements of Inco

Consolidated Statements of Income (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 28, 2018	Sep. 30, 2019	Sep. 28, 2018
Income Statement [Abstract]
Revenues	$ 1,023,277	$ 976,157	$ 2,917,424	$ 2,631,568
Direct costs of contracts	798,552	783,018	2,297,512	2,054,201
Equity in earnings of unconsolidated joint ventures	7,274	12,707	29,305	25,577
Indirect, general and administrative expenses	178,550	150,733	581,428	422,028
Operating income	53,449	55,113	67,789	180,916
Interest income	427	351	1,129	2,358
Interest expense	(4,909)	(5,940)	(19,577)	(14,475)
Other income (expense), net	(3,127)	696	(1,580)	355
Gain associated with claim on long-term contract	0	0	0	74,578
Total other income (expense)	(7,609)	(4,893)	(20,028)	62,816
Income before income tax provision	45,840	50,220	47,761	243,732
Income tax benefit (provision)	15,453	(4,154)	67,063	(18,526)
Net income including noncontrolling interests	61,293	46,066	114,824	225,206
Net income attributable to noncontrolling interests	(4,481)	(4,844)	(8,012)	(10,316)
Net income attributable to Parsons Corporation	$ 56,812	$ 41,222	$ 106,812	$ 214,890
Earnings per share:
Basic and diluted	$ 0.57	$ 0.52	$ 1.19	$ 2.66

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 28, 2018	Sep. 30, 2019	Sep. 28, 2018
Statement Of Income And Comprehensive Income [Abstract]
Net income including noncontrolling interests	$ 61,293	$ 46,066	$ 114,824	$ 225,206
Other comprehensive income (loss), net of tax
Foreign currency translation adjustment, net of tax	171	2,303	4,958	(3,079)
Pension adjustments, net of tax	(9)	10	17	(27)
Comprehensive income including noncontrolling interests, net of tax	61,455	48,379	119,799	222,100
Comprehensive income attributable to noncontrolling interests, net of tax	(4,481)	(4,822)	(8,012)	(10,270)
Comprehensive income attributable to Parsons Corporation, net of tax	$ 56,974	$ 43,557	$ 111,787	$ 211,830

Consolidated Statements of Cash

Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2019	Sep. 28, 2018
Cash flows from operating activities:
Net income including noncontrolling interests	$ 114,824	$ 225,206
Adjustments to reconcile net income to net cash used in operating activities
Depreciation and amortization	92,692	46,656
Amortization of deferred gain	0	(5,440)
Amortization of debt issue costs	802	548
Gain associated with claim on long-term contract	0	(129,674)
Loss on disposal of property and equipment	1,045	59
Provision for doubtful accounts	(964)	9,094
Deferred taxes	(105,161)	1,281
Foreign currency transaction gains and losses	1,689	2,007
Equity in earnings of unconsolidated joint ventures	(29,305)	(25,577)
Return on investments in unconsolidated joint ventures	32,848	31,728
Stock-based compensation	9,224
Contributions of treasury stock	36,779	34,070
Changes in assets and liabilities, net of acquisitions and newly consolidated joint ventures:
Accounts receivable	(31,726)	384,216
Contract assets	(59,161)	(527,768)
Prepaid expenses and current assets	2,980	(13,028)
Accounts payable	(6,946)	38,424
Accrued expenses and other current liabilities	40,186	9,558
Billings in excess of costs	0	(151,892)
Contract liabilities	20,703	168,579
Provision for contract losses	0	(13,992)
Income taxes	(3,019)	3,250
Other long-term liabilities	13,138	12,517
Net cash provided by operating activities	130,628	99,822
Cash flows from investing activities:
Capital expenditures	(44,030)	(19,436)
Proceeds from sale of property and equipment	2,824	112
Payments for acquisitions, net of cash acquired	(495,690)	(481,163)
Investments in unconsolidated joint ventures	(11,446)	(4,276)
Return of investments in unconsolidated joint ventures	6,632	1,126
Net cash used in investing activities	(541,710)	(503,637)
Cash flows from financing activities:
Proceeds from borrowings	530,000	260,000
Repayments of borrowings	(710,000)	(20,000)
Payments for debt costs and credit agreement	(286)	(468)
Contributions by noncontrolling interests	8,999	13,768
Distributions to noncontrolling interests	(35,378)	(6,858)
Purchase of treasury stock	(819)	(73,308)
IPO proceeds, net	536,879	0
Dividend paid	(52,093)	0
Net cash provided by financing activities	277,302	173,134
Effect of exchange rate changes	(953)	(1,233)
Net decrease in cash, cash equivalents, and restricted cash	(134,733)	(231,914)
Cash, cash equivalents and restricted cash:
Cash, cash equivalents and restricted cash, beginning of period	281,195	446,144
Cash, cash equivalents and restricted cash, end of period	$ 146,462	$ 214,230

Consolidated Statements of Shar

Consolidated Statements of Shareholder's Equity (Deficit) (Unaudited) - USD ($) $ in Thousands	Total	IPO	Redeemable Common Stock	Common Stock	Common StockIPO	Treasury Stock	Additional Paid-In Capital	Additional Paid-In CapitalIPO	Retained Earnings (Accumulated Deficit)	Accumulated Other Comprehensive Income (Loss)	Total Parsons Deficit	Total Parsons DeficitIPO	Noncontrolling Interest	Noncontrolling InterestIPO
Beginning balance at Dec. 29, 2017	$ (1,049,916)					$ (876,372)			$ (186,035)	$ (15,003)	$ (1,077,410)		$ 27,494
Beginning balance, Temporary Equity at Dec. 29, 2017			$ 1,855,305
Comprehensive income
Net income	225,206								214,890		214,890		10,316
Foreign currency translation gain (loss), net	(3,079)									(3,063)	(3,063)		(16)
Pension adjustments, net	(27)									(27)	(27)
Adjustment due to adoption of ASC | ASC 606	(4,632)								(4,735)		(4,735)		103
Purchase of treasury stock	0					(73,308)			73,308		0
Contributions	13,768												13,768
Distributions	(6,858)												(6,858)
Ending Balance at Sep. 28, 2018	(825,538)			$ 0		(949,680)	$ 0		97,428	(18,093)	(870,345)		44,807
Ending Balance, Temporary Equity at Sep. 28, 2018			1,781,997
Comprehensive income
Temporary equity, Purchase of treasury stock			(73,308)
Beginning balance at Jun. 29, 2018	(869,936)			0		(909,368)	0		15,894	(20,397)	(913,871)		43,935
Beginning balance, Temporary Equity at Jun. 29, 2018			1,822,309
Comprehensive income
Net income	46,066								41,222		41,222		4,844
Foreign currency translation gain (loss), net	2,303									2,294	2,294		9
Pension adjustments, net	10									10	10
Purchase of treasury stock	0					(40,312)			40,312		0
Contributions	115												115
Distributions	(4,096)												(4,096)
Ending Balance at Sep. 28, 2018	(825,538)			0		(949,680)	0		97,428	(18,093)	(870,345)		44,807
Ending Balance, Temporary Equity at Sep. 28, 2018			1,781,997
Comprehensive income
Temporary equity, Purchase of treasury stock			(40,312)
Beginning balance at Dec. 31, 2018	(921,076)			0		(957,025)	0		12,445	(22,957)	(967,537)		46,461
Beginning balance, Temporary Equity at Dec. 31, 2018	1,876,309		1,876,309
Comprehensive income
Net income	114,824								106,812		106,812		8,012
Foreign currency translation gain (loss), net	4,958									4,958	4,958		0
Pension adjustments, net	17									17	17
Adjustment due to adoption of ASC | ASC 842	52,608								52,608		52,608
Purchase of treasury stock	0					(819)			819		0
Contributions	8,999												8,999
Distributions	(35,378)												(35,378)
Dividend paid	(52,093)								(52,093)		(52,093)		0
Stock-based compensation	9,224						9,224				9,224
Conversion of S-Corp to C-Corp	(25,877)								(25,877)		(25,877)
Temporary equity, Conversion of S-Corp to C-Corp			25,877
IPO proceeds, net		$ 536,878			$ 21,296			$ 515,582				$ 536,878		$ 0
Accretion of redeemable common stock	(675,644)						(516,034)		(159,610)		(675,644)
Temporary equity, Accretion of redeemable common stock			675,644
Ending Balance at Sep. 30, 2019	(982,560)			21,296		(957,844)	8,772		(64,896)	(17,982)	(1,010,654)		28,094
Ending Balance, Temporary Equity at Sep. 30, 2019	2,577,011		2,577,011
Comprehensive income
Temporary equity, Purchase of treasury stock			(819)
Beginning balance at Jun. 30, 2019	(1,342,226)			21,296		(957,844)	0		(424,886)	(18,144)	(1,379,578)		37,352
Beginning balance, Temporary Equity at Jun. 30, 2019			2,880,189
Comprehensive income
Net income	61,293								56,812		56,812		4,481
Foreign currency translation gain (loss), net	171									171	171		0
Pension adjustments, net	(9)									(9)	(9)
Contributions	852												852
Distributions	(14,591)												(14,591)
Stock-based compensation	9,224						9,224				9,224
IPO proceeds, net		$ (452)						$ (452)				$ (452)
Accretion of redeemable common stock	303,178								303,178		303,178
Temporary equity, Accretion of redeemable common stock			(303,178)
Ending Balance at Sep. 30, 2019	(982,560)			$ 21,296		$ (957,844)	$ 8,772		$ (64,896)	$ (17,982)	$ (1,010,654)		$ 28,094
Ending Balance, Temporary Equity at Sep. 30, 2019	$ 2,577,011		$ 2,577,011

Description of Operations

Description of Operations	9 Months Ended
	Sep. 30, 2019
Description Of Operations Disclosure [Abstract]
Description of Operations	1. Description of Operations Organization Parsons Corporation, a Delaware corporation, and its subsidiaries (collectively, the “Company”) provide sophisticated design, engineering and technical services, and smart and agile software to the United States federal government and Critical Infrastructure customers worldwide. The Company performs work in various foreign countries through local subsidiaries, joint ventures and foreign offices maintained to carry out specific projects. Initial Public Offering On May 8, 2019, the Company consummated its initial public offering (“IPO”) whereby the Company sold 18,518,500 shares of common stock for $27.00 per share. The underwriters exercised their share option on May 14, 2019 to purchase an additional 2,777,775 shares at the share price of $25.515 which was the IPO share price of $27.00 less the underwriting discount of $1.485 per share. The net proceeds of the IPO and the underwriters’ share option were $536.9 million, after deducting underwriting discounts and other fees, and were used to fund an IPO dividend of $52.1 million, repay the outstanding balance of $150.0 million under our Term Loan, and repay outstanding indebtedness under our Revolving Credit Facility. Stock Dividend On April 15, 2019, the board of directors of the Company declared a common stock dividend in a ratio of two shares of common stock for every one share of common stock presently held by the Company’s stockholder (the “Stock Dividend”). The record date of this common Stock Dividend, which the Company refers to as the Stock Dividend was May 7, 2019, the day immediately prior to the consummation of the Company’s IPO on May 8, 2019, and the payment date of the Stock Dividend was May 8, 2019. Purchasers of the Company’s common stock in the Company’s public offering were not entitled to receive any portion of the Stock Dividend.

Basis of Presentation and Princ

Basis of Presentation and Principles of Consolidation	9 Months Ended
	Sep. 30, 2019
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Basis of Presentation and Principles of Consolidation	2 . The accompanying unaudited consolidated financial statements and related notes of the Company have been prepared in accordance with generally accepted accounting principles in the United States of America ("GAAP") and pursuant to the interim period reporting requirements of Form 10-Q. They do not include all of the information and footnotes required by GAAP for complete financial statements and, therefore, should be read in conjunction with our consolidated financial statements and the notes thereto included in the Company’s Form S-1/A filed on April 29, 2019. In the opinion of management, the consolidated financial statements reflect all normal recurring adjustments necessary for a fair statement of the financial position, results of operations and cash flows for the interim periods presented. The results of operations and cash flows for any interim period are not necessarily indicative of results for the full year or for future years. This Quarterly Report on Form 10-Q includes the accounts of our wholly-owned subsidiaries, and joint ventures of which we are the primary beneficiary. The equity method of accounting is applied for the joint ventures in which the Company does not have a controlling interest, but exerts a significant influence (see “Note 15 – In the first quarter of 2019 the Company adopted Accounting Standards Update (‘ASU”) 2016-02, “Leases” (“Topic 842”), using the modified retrospective method. The new guidance was applied to leases that existed or were entered into on or after January 1, 2019. The Company’s results for the reporting period beginning January 1, 2019 have been presented under Topic 842, while prior period amounts have not been adjusted and continue to be reported in accordance with previous guidance. See “Note 6 – Leases” for further discussion of the adoption and the impact on the Company’s financial statements. Accumulated Deficit The Company's accounting policy is to record dividends and accretion of redeemable stock as a reduction of retained earnings. In the absence of retained earnings, the Company will charge the dividends and/or accretion of redeemable stock to Additional Paid-in Capital Fiscal Periods In October 2018, our board of directors approved a change in our annual and quarterly fiscal period ends from the last Friday on or before the calendar year or quarterly month-end to the last day of the calendar year or quarterly month-end. Accordingly, the period end for the first, second, and third quarters of fiscal 2018 and fiscal 2019 are March 30, 2018, June 29, 2018, and September 28, 2018, respectively, and March 31, 2019, June 30, 2019, and September 30, 2019, respectively. The number of days in the three- and nine-month periods ended September 28, 2018 and September 30, 2019 were 91 and 273, respectively, and 92 and 273, respectively. Use of Estimates The preparation of the consolidated financial statements in accordance with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Actual amounts could differ from those estimates. The Company’s most significant estimates and judgments involve revenue recognition with respect to the determination of the costs to complete contracts and transaction price; determination of self-insurance reserves; valuation of the Company’s fair value of common stock (for periods prior to the IPO); useful lives of property and equipment and intangible assets; calculation of allowance for doubtful accounts; valuation of deferred income tax assets and uncertain tax positions, among others. Please see “Note 2 – Summary of Significant Accounting Policies” of Notes to Consolidated Financial Statements included in the Company’s Form S-1/A filed April 29, 2019, for a discussion of the significant estimates and assumptions affecting our consolidated financial statements. Estimates of costs to complete contracts are continually evaluated as work progresses and are revised when necessary. When a change in estimate is determined to have an impact on contract profit, the Company records a positive or negative adjustment to the consolidated statement of income. Inventory Included in Prepaid expenses and other current assets Redeemable Common Stock In connection with the Company’s IPO on May 8, 2019, all Employee Stock Ownership Plan (“ESOP”) shares were contingently redeemable for cash during the 180-day lock-up period which ended on November 3, 2019. During the 180-day lock-up period, the Company presented all shares held by the ESOP as temporary equity on the consolidated balance sheets as Redeemable common stock held by Employee Stock Ownership Plan (ESOP)

Recently Adopted Accounting Pro

Recently Adopted Accounting Pronouncements	9 Months Ended
	Sep. 30, 2019
Accounting Policies [Abstract]
Recently Adopted Accounting Pronouncements	3 . In the first quarter of 2019, the Company adopted Topic 842. See “Note 6 – Leases” for further discussion of the adoption and the impact on the Company’s financial statements. In the first quarter of 2019, the Company adopted ASU 2018-02, “Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income” under which the Company did not elect to reclassify the income tax effects stranded in accumulated other comprehensive income to retained earnings as a result of the enactment of comprehensive tax legislation, commonly referred to as the Tax Cuts and Jobs Act. As a result, there was no impact on the Company’s financial position, results of operations or cash flows. On December 30, 2017, the Company adopted ASC 606, “Revenue from Contracts with Customers,” using the modified retrospective method, which provides for a cumulative effect adjustment to retained earnings beginning in fiscal 2018 for those uncompleted contracts impacted by the adoption of the new standard. The difference between the recognition criteria under ASC 606 and our previous recognition practices under ASC 605-35 was recognized through a cumulative adjustment of $4.7 million that was made to the opening balance of accumulated deficit as of December 30, 2017. In January 2017, the Financial Accounting Standards Board (“FASB”) issued ASU 2017-04, Simplifying the Test for Goodwill Impairment. ASU 2017-04 simplifies the test for goodwill impairment by removing the second step of the goodwill impairment test, which requires a hypothetical purchase price allocation. A goodwill impairment will now be the amount by which a reporting unit’s carrying value exceeds its fair value, not to exceed the carrying amount of goodwill. The guidance is effective for interim and annual reporting periods beginning after December 15, 2019 and should be applied prospectively with early adoption permitted. The Company early adopted the new standard as of the beginning of fiscal 2018 and its adoption did not have a material impact on the consolidated financial statements.

Acquisitions

Acquisitions	9 Months Ended
	Sep. 30, 2019
Business Combinations [Abstract]
Acquisitions	4 . Polaris Alpha On May 31, 2018, the Company acquired a 100% ownership interest in Polaris Alpha, a privately owned, advanced technology-focused provider of innovative mission solutions for complex defense, intelligence, and security customers, as well as other U.S. federal government customers, for $489.1 million paid in cash. The Company borrowed $260 million under the credit agreement, as described in “Note 11 – Debt and Credit Facilities,” to partially fund the acquisition. In connection with this acquisition, the Company recognized $6.2 million of acquisition-related expenses in “Indirect, general and administrative expense” in the consolidated statements of income for the fiscal year ended December 31, 2018, including legal fees, consulting fees, and other miscellaneous direct expenses associated with the acquisition. Polaris Alpha enhances the Company’s artificial intelligence and data analytics expertise with new technologies and solutions. Customers of both companies will benefit from existing, complementary technologies and increased scale, enabling end-to-end solutions under the shared vision of rapid prototyping and agile development. The following table summarizes the estimated fair values of the assets acquired and liabilities assumed (in thousands): Amount Cash and cash equivalents $ 7,914 Accounts receivable 29,688 Contract assets 35,229 Prepaid expenses and other current assets 9,295 Property and equipment 9,024 Goodwill 243,471 Intangible assets 199,520 Other noncurrent assets 2,203 Accounts payable (13,942 ) Accrued expenses and other current liabilities (26,419 ) Contract liabilities (3,529 ) Deferred tax liabilities (2,231 ) Other long-term liabilities (1,146 ) Net assets acquired $ 489,077 Of the total purchase price, the following values were assigned to intangible assets (in thousands, except for years): Gross Carrying Amount Amortization Period (in years) Developed technology $ 84,900 4 Customer relationships 76,000 8 Backlog 34,900 2 Trade name 3,600 1 Leases $ 120 6 Amortization expense of $13.0 million and $13.2 million related to these intangible assets was recorded for the three months ended September 28, 2018 and September 30, 2019, respectively, and $17.3 million and $41.2 million for the nine months ended September 28, 2018 and September 30, 2019, respectively. The entire value of goodwill of $243.5 million was assigned to the Parsons Federal reporting unit and represents synergies expected to be realized from this business combination. Goodwill of $50.1 million is The amount of revenue generated by Polaris Alpha and included within consolidated revenues is $94.8 million and $96.9 million for the three months ended September 28, 2018 and September 30, 2019, respectively, and $124.7 million and $293.0 million for the nine months ended September 28, 2018 and September 30, 2019, respectively. The Company has determined that the presentation of net income from the date of acquisition is impracticable due to the integration of general corporate functions upon acquisition. Supplemental Pro Forma Information Supplemental information on an unaudited pro forma operating results assuming the Polaris Alpha acquisition had been consummated as of the beginning of fiscal year 2018 (December 31, 2017) (in thousands) is as follows: Three Months Ended Nine Months Ended September 28, 2018 September 28, 2018 Pro forma revenue $ 976,157 $ 2,784,864 Pro forma net income including noncontrolling interests $ 46,848 $ 179,071 The unaudited pro forma supplemental information is based on estimates and assumptions which the Company believes are reasonable and reflects the pro forma impact of additional amortization related to the fair value of acquired intangible assets, pro forma impact of reflecting acquisition costs, which consisted of legal, advisory and due diligence fees and expenses and the additional pro forma interest expense related to the borrowings under the credit agreement as of the assumed acquisition date. This supplemental pro forma information has been prepared for comparative purposes and does not purport to be indicative of what would have occurred had the acquisition been consummated during the periods for which pro forma information is presented. OGSystems On January 7, 2019, the Company acquired a 100% ownership interest in OGSystems, a privately owned company, for $292.4 million paid in cash. OGSystems provides geospatial intelligence, big data analytics and threat mitigation for defense and intelligence customers. The Company borrowed $110 million under the credit agreement and $150 million on a short-term loan, as described in “Note 11 – Debt and Credit Facilities,” to partially fund the acquisition. In connection with this acquisition, the Company recognized $0.6 million and $5.5 million of acquisition-related expenses in “Indirect, general and administrative expense” in the consolidated statements of income for the three and nine months ended September 30, 2019, respectively, including legal fees, consulting fees, and other miscellaneous direct expenses associated with the acquisition. OGSystems enhances the Company’s artificial intelligence and data analytics expertise with new technologies and solutions. Customers of both companies will benefit from existing, complementary technologies and increased scale, enabling end-to-end solutions under the shared vision of rapid prototyping and agile development. The following table summarizes the estimated fair values of the assets acquired and liabilities assumed based on the preliminary purchase price allocation as of the date of acquisition (in thousands): Amount Cash and cash equivalents $ 5,772 Accounts receivable 9,904 Contract assets 9,747 Prepaid expenses and other current assets 4,307 Property and equipment 4,085 Right of use assets, operating leases 8,826 Goodwill 183,540 Intangible assets 92,300 Other noncurrent assets 10 Accounts payable (5,450 ) Accrued expenses and other current liabilities (7,147 ) Contract liabilities (1,300 ) Short-term lease liabilities, operating leases (805 ) Income tax payable (1,469 ) Deferred tax liabilities (904 ) Long-term lease liabilities, operating leases (8,021 ) Other long-term liabilities (1,015 ) Net assets acquired $ 292,380 Of the total purchase price, the following values were assigned to intangible assets (in thousands, except for years): Gross Carrying Amount Amortization Period (in years) Customer relationships $ 57,100 5 Backlog 27,700 3 Trade name 3,800 2 Non-compete agreements 2,400 3 Developed technologies $ 1,300 3 The Company is still in the process of finalizing its valuation of developed technology acquired. Amortization expense of $5.9 million and $17.8 million related to these intangible assets was recorded for the three and nine months ended September 30, 2019, respectively. The entire value of goodwill of $183.5 million was assigned to the Parsons Federal reporting unit and represents synergies expected to be realized from this business combination. Goodwill of $16.0 million is deductible for tax purposes. The amount of revenue generated by OGSystems since the acquisition and included within consolidated revenues for the three and nine months ended September 30, 2019 is $33.7 million and $108.7 million, respectively. The Company has determined that the presentation of net income from the date of acquisition is impracticable due to the integration of general corporate functions upon acquisition. Supplemental Pro Forma Information Supplemental information on an unaudited pro forma operating results assuming the OGSystems acquisition had been consummated as of the beginning of fiscal year 2018 (December 31, 2017) (in thousands) is as follows: Three Months Ended Nine Months Ended September 28, 2018 September 30, 2019 September 28, 2018 September 30, 2019 Pro forma revenue $ 1,007,793 $ 1,023,277 $ 2,715,572 $ 2,919,379 Pro forma net income including noncontrolling interests $ 39,224 $ 61,293 $ 196,905 $ 118,896 The unaudited pro forma supplemental information is based on estimates and assumptions which the Company believes are reasonable and reflects the pro forma impact of additional amortization related to the fair value of acquired intangible assets, pro forma impact of reflecting acquisition costs, which consisted of legal, advisory and due diligence fees and expenses and the additional pro forma interest expense related to the borrowings under the credit agreement as of the assumed acquisition date. This supplemental pro forma information has been prepared for comparative purposes and does not purport to be indicative of what would have occurred had the acquisition been consummated during the periods for which pro forma information is presented. QRC Technologies On July 31, 2019 the Company acquired a 100% ownership interest in QRC Technologies (“QRC”), a privately owned company, for $214.1 million in cash. QRC provides design and development of open-architecture radio-frequency products. The company borrowed $140.0 million under the Revolving Credit Facility to partially fund the transaction. In connection with this acquisition, the Company recognized $4.7 million of acquisition-related expenses in “Indirect, general and administrative expense” in the consolidated statements of income for the three and nine months ended September 30, 2019 including legal fees, consulting fees, and other miscellaneous direct expenses associated with the acquisition. QRC is an agile, disruptive product company that specializes in radio frequency spectrum survey, record and playback; signals intelligence; and electronic warfare missions. QRC complements our existing portfolio, increases our presence in the high-growth markets of spectrum awareness and surveillance, adds critical intellectual property that complements and expands our available capabilities for the Special Operations and Intelligence Communities. The following table summarizes the estimated fair values of the assets acquired and liabilities assumed based on the preliminary purchase price allocation as of the date of acquisition (in thousands): Amount Cash and cash equivalents $ 5,925 Accounts receivable 5,587 Prepaid expenses and other current assets 5,467 Property and equipment 1,205 Right of use assets, operating leases 5,228 Goodwill 128,387 Intangible assets 72,900 Accounts payable (1,567 ) Accrued expenses and other current liabilities (3,771 ) Short-term lease liabilities, operating leases (545 ) Long-term lease liabilities, operating leases (4,683 ) Net assets acquired $ 214,133 Of the total purchase price, the following values were assigned to intangible assets (in thousands, except for years): Gross Carrying Amount Amortization Period (in years) Customer relationships $ 47,600 12 Backlog 700 1 Trade name 800 2 Non-compete agreements 1,200 4 Developed technologies $ 22,600 3-5 The Company is still in the process of finalizing its valuation of the net assets acquired. Amortization expense of $1.9 million related to these intangible assets was recorded for the three and nine months ended September 30, 2019, respectively. The entire value of goodwill of $128.4 million was assigned to the Parsons Federal reporting unit and represents synergies expected to be realized from this business combination. Goodwill in it’s entirety is deductible for tax purposes. The amount of revenue generated by QRC since the acquisition and included within consolidated revenues for both the three and nine months ended September 30, 2019 is $5.6 million. The Company has determined that the presentation of net income from the date of acquisition is impracticable due to the integration of general corporate functions upon acquisition. Supplemental Pro Forma Information Supplemental information on an unaudited pro forma operating results assuming the QRC Technologies acquisition had been consummated as of the beginning of fiscal year 2018 (December 31, 2017) (in thousands) is as follows: Three Months Ended Nine Months Ended September 28, 2018 September 30, 2019 September 28, 2018 September 30, 2019 Pro forma revenue $ 987,343 $ 1,026,831 $ 2,657,105 $ 2,938,973 Pro forma net income including noncontrolling interests $ 44,944 $ 65,782 $ 212,728 $ 117,399

Contracts with Customers

Contracts with Customers	9 Months Ended
	Sep. 30, 2019
Revenue From Contract With Customer [Abstract]
Contracts with Customers	5 . Contracts with Customers Disaggregation of Revenue The Company’s contracts contain both fixed-price and cost reimbursable components. Contract types are based on the component that represents the majority of the contract. The following table presents revenue disaggregated by contract type (in thousands): Three Months Ended Nine Months Ended September 28, 2018 September 30, 2019 September 28, 2018 September 30, 2019 Fixed-Price $ 300,225 $ 288,316 $ 833,224 $ 850,658 Time-and-Materials 254,435 285,586 732,555 810,656 Cost-Plus 421,497 449,375 1,065,789 1,256,110 Total $ 976,157 $ 1,023,277 $ 2,631,568 $ 2,917,424 See “Note 19 – Segments Information” for the Company’s revenues by business lines. Contract Assets and Contract Liabilities Contract assets and contract liabilities balances at December 31, 2018 and September 30, 2019 were as follows (in thousands): December 31, 2018 September 30, 2019 $ change % change Contract assets $ 515,319 $ 583,670 $ 68,351 13.3 % Contract liabilities 208,576 231,032 22,456 10.8 % Net contract assets (liabilities) (1) $ 306,743 $ 352,638 $ 45,895 15.0 % (1) During the three months ended September 28, 2018 and September 30, 2019, the Company recognized revenue of $0.8 million and December 31, 2018 September 30, 2019 Acquired contract assets $ 35,229 $ 9,747 Acquired contract liabilities 3,529 1,300 Change in the estimate of variable consideration - 14,506 Reversal of provision for contract losses (1) $ 133,180 $ - (1) Reversal of provision for contract losses of $133.2 million, of which $55.1 million was recorded as an increase in revenue with the remainder recorded as other income. There was no significant impairment of contract assets recognized during the three and nine months ended September 28, 2018 and September 30, 2019. Revisions in estimates, such as changes in estimated claims or incentives, related to performance obligations partially satisfied in previous periods that individually had an impact of $5 million or more on revenue resulted in an increase in revenue of $9.1 million for the three and nine months ended September 30, 2019, and no amounts for the three and nine months ended September 28, 2018. Accounts Receivable, net Accounts receivable, net consisted of the following as of December 31, 2018 and September 30, 2019 (in thousands): December 31, 2018 September 30, 2019 Billed $ 538,808 $ 516,099 Unbilled 135,180 200,477 Total accounts receivable, gross 673,988 716,576 Allowance for doubtful accounts (50,702 ) (42,902 ) Total accounts receivable, net $ 623,286 $ 673,674 Billed accounts receivable represents amounts billed to clients that have not been collected. Unbilled accounts receivable represents amounts where the Company has a present contractual right to bill but an invoice has not been issued to the customer at the period-end date. The allowance for doubtful accounts was determined based on consideration of trends in actual and forecasted credit quality of clients, including delinquency and payment history, type of client, such as a government agency or commercial sector client, and general economic conditions and particular industry conditions that may affect a client’s ability to pay. Transaction Price Allocated to the Remaining Unsatisfied Performance Obligations The Company’s remaining unsatisfied performance obligations (“RUPO”) as of September 30, 2019 represent a measure of the total dollar value of work to be performed on contracts awarded and in progress. The Company had $5.1 billion in RUPO as of September 30, 2019. RUPO will increase with awards of new contracts and decrease as the Company performs work and recognizes revenue on existing contracts. Projects are included within RUPO at such time the project is awarded and agreement on contract terms has been reached. The difference between RUPO and backlog relates to unexercised option years that are included within backlog and the value of Indefinite Delivery/Indefinite Quantity (“IDIQ”) contracts included in backlog for which delivery orders have not been issued. RUPO is comprised of: (a) original transaction price, (b) change orders for which written confirmations from our customers have been received, (c) pending change orders for which the Company expects to receive confirmations in the ordinary course of business, and (d) claim amounts that the Company has made against customers for which it has determined that it has a legal basis under existing contractual arrangements and a significant reversal of revenue is not probable, less revenue recognized to-date. The Company expects to satisfy its RUPO as of September 30, 2019 over the following periods (in thousands): Period RUPO Will Be Satisfied Within One Year Within One to Two Years Thereafter Federal Solutions $ 1,198,634 $ 436,620 $ 208,734 Critical Infrastructure 1,636,525 960,469 643,170 Total $ 2,835,159 $ 1,397,089 $ 851,904

Leases

Leases	9 Months Ended
	Sep. 30, 2019
Leases [Abstract]
Leases	6 . In February 2016, the FASB issued ASU 2016-02 “Leases (Topic 842)”, which is a new standard related to leases to increase transparency and comparability among organizations by requiring the recognition of right-of-use (“ROU”) assets obtained in exchange for lease liabilities on the balance sheet. Most prominent among the changes in the standard is the recognition of ROU assets and lease liabilities by lessees for those leases classified as operating leases. Under the standard, disclosures are required to meet the objective of enabling users of financial statements to assess the amount, timing, and uncertainty of cash flows arising from leases. The Company elected to adopt the standard, and available practical expedients, effective January 1, 2019. These practical expedients allowed the Company to keep the lease classification assessed under the previous lease accounting standard (ASC 840) without reassessment under the new standard, and allowed all separate lease components, including non-lease components, to be accounted for as a single lease component for all existing leases prior to adoption of the new standard. Furthermore, the Company made an accounting policy election to not recognize a lease liability and ROU asset for leases with lease terms of twelve months or less. The Company adopted this new standard under the modified retrospective transition approach without adjusting comparative periods in the financial statements, as allowed under Topic 842, and implemented internal controls and key system functionality to enable the preparation of financial information on adoption. The standard had a material impact on the Company’s consolidated balance sheets but did not have an impact on the consolidated income statements. The most significant impact was the recognition of ROU assets and lease liabilities for operating leases, while accounting for finance leases remained substantially unchanged. As a result of the adoption, the Company recorded a cumulative-effect adjustment to retained earnings of $52.6 million net of deferred tax asset adjustment of $0.7 million, representing the unamortized portion of a deferred gain previously recorded as a sale-leaseback transaction associated with the sale of an office building in 2011. The Company concluded the transaction resulted in the transfer of control of the office building to the buyer-lessor at market terms and would have qualified as a sale under Topic 842 with gain recognition in the period the sale was recognized. The Company determines if an arrangement is a lease at inception. Operating leases are included in operating lease ROU assets and current and long-term operating lease liabilities in the consolidated balance sheets. Finance leases are included in other noncurrent assets, accrued expenses and other current liabilities and other long-term liabilities in the consolidated balance sheets. ROU assets represent the Company’s right to use an underlying asset for the lease term and lease liabilities represent our obligation to make lease payments arising from the lease. Operating lease ROU assets and liabilities are recognized at commencement date based on the present value of lease payments over the lease term. As most of the Company’s leases do not provide an implicit rate, incremental borrowing rates are used based on the information available at commencement date in determining the present value of lease payments. The operating lease ROU asset also includes any lease payments made and excludes lease incentives. Lease terms may include options to extend or terminate the lease when it is reasonably certain that we will exercise that option. Lease expense for operating lease payments is recognized on a straight-line basis over the lease term. We have lease agreements with lease and non-lease components, which are generally accounted for separately. For certain equipment leases, such as vehicles, we account for the lease and non-lease components as a single lease component. Additionally, for certain equipment leases, we apply a portfolio approach to effectively account for the operating lease ROU assets and liabilities. The Company has operating and finance leases for corporate and project office spaces, vehicles, heavy machinery and office equipment. Our leases have remaining lease terms of one year to 10 years, some of which may include options to extend the leases for up to five years, and some of which may include options to terminate the leases up to the seventh year. As of September 30, 2019, assets recorded under finance leases were $1.8 million The components of lease costs for the three and nine months ended September 30, 2019 are as follows (in thousands): Three Months Ended Nine Months Ended September 30, 2019 September 30, 2019 Operating lease cost $ 17,969 $ 53,835 Short-term lease cost 5,429 10,925 Amortization of right-of-use assets 120 455 Interest on lease liabilities 15 46 Sublease income (712 ) (2,727 ) Total lease cost $ 22,821 $ 62,534 Supplemental cash flow information related to leases for the nine months ended September 30, 2019 is as follows (in thousands): Nine Months Ended September 30, 2019 Operating cash flows for operating leases $ 52,056 Operating cash flows for financing activities 570 Right-of-use assets obtained in exchange for new operating lease liabilities 274,212 Right-of-use assets obtained in exchange for new finance lease liabilities $ 1,818 Supplemental balance sheet and other information related to leases as of September 30, 2019 is as follows (in thousands): September 30, 2019 Operating Leases: Right-of-use assets $ 219,207 Lease liabilities: Current $ 49,074 Long-term 188,571 Total operating lease liabilities $ 237,645 Finance Leases: Other noncurrent assets $ 1,362 Lease liabilities: Accrued expenses and other current liabilities $ 558 Other long-term liabilities 736 Total finance lease liabilities $ 1,294 Weighted Average Remaining Lease Term: Operating leases 6 years Finance leases 3 years Weighted Average Discount Rate: Operating leases 4.3 % Finance leases 4.4 % As of September 30, 2019, the Company has additional operating leases, primarily for office spaces, that have not yet commenced of $37.0 million. These operating leases will commence in 2019 with lease terms of 2 years to 11 years. A maturity analysis of the future undiscounted cash flows associated with the Company’s operating and finance lease liabilities as of September 30, 2019 is as follows (in thousands): Operating Leases Finance Leases 2019 $ 15,409 $ 160 2020 54,561 574 2021 50,333 421 2022 44,160 187 2023 36,996 25 Thereafter 64,423 - Total lease payments 265,882 1,367 Less: imputed interest (28,237 ) (73 ) Total present value of lease liabilities $ 237,645 $ 1,294 As of December 31, 2018, $276.7 million of minimum rental commitments on operating leases was payable as follows: $67.9 million in 2019, $51.0 million in 2020, $42.5 million in 2021, $35.9 million in 2022, $29.4 million in 2023, and $50.0 million thereafter. Rental expense for the three and nine months ended September 28, 2018 was $21.7 million and $59.7 million, respectively.

Goodwill

Goodwill	9 Months Ended
	Sep. 30, 2019
Goodwill And Intangible Assets Disclosure [Abstract]
Goodwill	7 . The following table summarizes the changes in the carrying value of goodwill by reporting segment at December 31, 2018 and September 30, 2019 (in thousands): December 31, 2018 Acquisitions Foreign Exchange September 30, 2019 Federal Solutions $ 666,841 $ 311,860 $ - $ 978,701 Critical Infrastructure 70,097 - 1,279 71,376 Total $ 736,938 $ 311,860 $ 1,279 $ 1,050,077

Intangible Assets

Intangible Assets	9 Months Ended
	Sep. 30, 2019
Goodwill And Intangible Assets Disclosure [Abstract]
Intangible Assets	8 . The gross amount and accumulated amortization of intangible assets with finite useful lives included in “Intangible assets, net” on the consolidated balance sheets are as follows (in thousands except for years): December 31, 2018 September 30, 2019 Weighted Average Gross Carrying Amount Accumulated Amortization Net Carrying Amount Gross Carrying Amount Accumulated Amortization Net Carrying Amount Amortization Period (in years) Backlog $ 80,754 $ (58,295 ) $ 22,459 $ 109,155 $ (80,321 ) $ 28,834 3 Customer relationships 121,629 (38,974 ) 82,655 226,329 (60,266 ) 166,063 7 Leases 670 (561 ) 109 670 (576 ) 94 5 Developed technology 87,839 (15,174 ) 72,665 111,739 (32,545 ) 79,194 4 Trade name 3,600 (2,100 ) 1,500 8,200 (5,092 ) 3,108 1 Non-compete agreements - - - 3,600 (650 ) 2,950 3 Other intangibles 275 (145 ) 130 1,076 (162 ) 914 10 Total intangible assets $ 294,767 $ (115,249 ) $ 179,518 $ 460,769 $ (179,612 ) $ 281,157 The aggregate amortization expense of intangible assets for the three months ended September 28, 2018 and September 30, 2019 was $14.8 million and $22.1 million, respectively, and for the nine months ended September 30, 2018 and September 30, 2019 was $22.7 million and $64.5 million, respectively. Estimated amortization expense in each of the next five years and beyond is as follows (in thousands): September 30, 2019 2019 (remaining) $ 23,049 2020 83,511 2021 78,778 2022 34,517 2023 22,599 Thereafter 38,703 Total $ 281,157

Property and Equipment, Net

Property and Equipment, Net	9 Months Ended
	Sep. 30, 2019
Property Plant And Equipment [Abstract]
Property and Equipment, Net	9 . Property and equipment consisted of the following at December 31, 2018 and September 30, 2019 (in thousands): December 31, 2018 September 30, 2019 Useful lives (years) Buildings and leasehold improvements $ 54,348 $ 71,698 1-15 Furniture and equipment 81,705 85,322 3-10 Computer systems and equipment 148,255 168,241 3-10 Construction equipment 12,074 11,753 5-7 Accumulated depreciation (204,533 ) (227,776 ) Property and equipment, net $ 91,849 $ 109,238 Depreciation expense for the three months ended September 28, 2018 and September 30, 2019 was

Sale-Leasebacks

Sale-Leasebacks	9 Months Ended
	Sep. 30, 2019
Leases [Abstract]
Sale-Leasebacks	1 0 . During fiscal 2011, the Company consummated two sale-leaseback transactions associated with the sale of two office buildings from which the Company recognized a total gain in the consolidated statements of income (loss) of $106.7 million and a total deferred gain of $107.8 million. The current and long-term portion of the deferred gain had been recorded in “Accrued expenses and other current liabilities” and “Deferred gain resulting from sale-leaseback transactions” on the consolidated balance sheet at December 31, 2018, respectively, and was being recognized ratably over the minimum lease terms to which they relate, as an offset to rental expense in “Indirect, general and administrative expenses” in the consolidated statements of income. Amortization of the deferred gain was $1.8 million

Debt and Credit Facilities

Debt and Credit Facilities	9 Months Ended
	Sep. 30, 2019
Debt Disclosure [Abstract]
Debt and Credit Facilities	1 1 . Debt consisted of the following (in thousands): Long-Term: December 31, 2018 September 30, 2019 Revolving credit facility $ 180,000 $ - Senior notes 250,000 250,000 Debt issuance costs (836 ) (694 ) Total long-term $ 429,164 $ 249,306 In November 2017, the Company entered into an amended and restated Credit Agreement. The Company incurred $2.0 million of costs in connection with this amendment. Under the agreement, the Company’s revolving credit facility was increased from $500 million to $550 million and the term of the agreement was extended through November 2022. The borrowings under the Credit Agreement bear interest, at the Company’s option, at either the Base Rate (as defined in the Credit Agreement), plus an applicable margin, or LIBOR plus an applicable margin. The applicable margin for Base Rate loans is a range of 0.125% to 1.00% and the applicable margin for LIBOR loans is a range of 1.125% to 2.00%, both based on the leverage ratio of the Company at the end of each fiscal quarter. The rates at December 31, 2018 and September 30, 2019 were 4.253% and 3.350%, respectively. Borrowings under this Credit Agreement are guaranteed by certain of the Company’s operating subsidiaries. Letters of credit commitments outstanding under this agreement aggregated to $49.8 million and $45.2 million at December 31, 2018 and September 30, 2019, respectively, which reduced borrowing limits available to the Company. Interest expense related to the credit agreement was $1.1 million and $6.4 million for the three and nine months ended September 30, 2019, respectively, and for the three and nine months ended September 28, 2018 was $2.5 million and $3.5 million, respectively. On July 1, 2014, the Company finalized a private placement whereby the Company raised an aggregate amount of $250.0 million in debt repayable as follows (in thousands): Tranche Debt Amount Maturity Date Interest Rates Senior Note, Series A $ 50,000 July 15, 2021 4.44 % Senior Note, Series B 100,000 July 15, 2024 4.98 % Senior Note, Series C 60,000 July 15, 2026 5.13 % Senior Note, Series D $ 40,000 July 15, 2029 5.38 % The Company incurred $1.1 million of debt issuance costs in connection with the private placement. On August 10, 2018, the Company finalized an amended and restated intercreditor agreement related to this private placement to more closely align certain covenants and definitions with the terms under the 2017 amended and restated Credit Agreement and incurred $0.5 million of additional issuance costs. These costs are presented as a direct deduction from the debt on the face of the consolidated balance sheets. Interest expense related to the Senior Notes for both the three and nine months ended September 28, 2018 and September 30, 2019 was $3.1 million and $9.3 million, respectively. The amortization of debt issuance costs and interest expense are recorded in “Interest expense” on the consolidated statements of income. The Company made interest payments related to the Senior Notes for both the three and nine months ended September 28, 2018 and September 30, 2019 of $6.2 million and $12.4 million, respectively. Interest payable of $5.7 million and $2.6 million is recorded in “Accrued expenses and other current liabilities” on the consolidated balance sheets at December 31, 2018 and September 30, 2019, respectively, related to the Senior Notes. The Credit Agreement and private placement includes various covenants, including restrictions on indebtedness, liens, acquisitions, investments or dispositions, payment of dividends and maintenance of certain financial ratios and conditions. The Company was in compliance with these covenants at December 31, 2018 and September 30, 2019. The Company also has in place several secondary bank credit lines for issuing letters of credit, principally for foreign contracts, to support performance and completion guarantees. Letters of credit commitments outstanding under these bank lines aggregated $223.0 million and $220.6 million at December 31, 2018 and September 30, 2019, respectively. Using a discounted cash flow technique that incorporates a market interest yield curve with adjustments for duration, optionality, and risk profile, the Company estimated the fair value (level 2) of its senior notes at September 30, 2019 approximates $269.3 million. See “Note 17 – Fair Value of Financial Instruments” for the definition of level 2 of the fair value hierarchy. In January 2019, the Company borrowed $150.0 million under our Term Loan Agreement to partially finance the OGSystems acquisition. On May 10, 2019, the Company used proceeds from its May 8, 2019 IPO to repay the $150.0 million outstanding balance under the Term Loan and this loan is now closed. Interest expense related to the term loan was $0 and $2.3 million for the three and nine months ended September 30, 2019, respectively. Amortization of debt issuance costs for all the Company’s debt and credit facilities for the three months ended September 28, 2018 and September 30, 2019 was $0.2 million and $0.2 million, respectively and $0.5 million and $0.8 million for the nine months ended September 28, 2018 and September 30, 2019, respectively.

Income Taxes

Income Taxes	9 Months Ended
	Sep. 30, 2019
Income Tax Disclosure [Abstract]
Income Taxes	1 2 . Historically, the Company had elected to be taxed under the provisions of Subchapter “S” of the Internal Revenue Code for federal tax purposes. As a result, income had not been subject to U.S. federal income taxes or state income taxes in those states where the “S” Corporation status is recognized. Therefore, previously, no provision or liability for federal or state income tax had been provided in the consolidated financial statements except for those states where the “S” Corporation status was not recognized, or where states imposed a tax on “S” Corporations. In connection with the Company’s IPO on May 8, 2019, the “S” Corporation status was terminated, and the Company is now treated as a “C” Corporation under the Code. The termination of the “S” Corporation election has had a material impact on the Company’s results of operations, financial condition, and cash flows as reflected in the June 30 and September 30, 2019 consolidated financial statements. The effective income tax rate has increased and net income has decreased as compared to the Company’s “S” Corporation tax years, since the Company is now subject to both U.S. federal and state corporate income taxes on its earnings. For US corporate income tax purposes, the Company will apportion its 2019 taxable income ratably between the “S” Corporation and “C” Corporation periods, as allowed by law. This allocation of income will effectively result in a blended income tax rate for the 2019 year, as only the C corporation earnings will be subject to both U.S. federal and state corporate income tax while the “S” Corporation earnings will be subject to tax in those states that tax “S” Corporations or do not recognize “S” Corporation status. The Company has estimated our 2019 effective tax benefit rate to be (69.69)%. The most significant item contributing to the difference between the effective rate and the statutory U.S. Federal income tax rate of 21.0% for the quarter ended September 30, 2019 is the tax impact of updating the revaluation of deferred tax assets and liabilities, resulting from the conversion from an “S” to a “C” Corporation. The termination for the “S” Corporation status has been treated as a change in tax status under Accounting Standards Codification 740, “Income Taxes”. These rules require that the deferred tax effects of a change in tax status be recorded to income from continuing operations on the date the “S” Corporation status terminates. During the quarter ended June 30, 2019 the Company recorded a discrete deferred tax benefit of $56 million for the estimated effect of the change in tax status, relating to the recognition of net deferred tax assets for temporary differences in existence on the date of conversion to a “C” Corporation. During the quarter ended September 30, 2019, the Company has updated the estimate to $85 million, representing an increase in expected benefit of $29 million. The update primarily relates to a change in the forecasted temporary differences as of the conversion, changes in deferred tax assets resulting from 2018 tax return-to-provision adjustments, and changes in tax accounting methods that were made with the 2018 tax return during the third quarter. This amount is subject to additional revision based upon actual results for the current year. The $29 million increase was recorded as a discrete tax benefit in the three months ended September 30, 2019. The US government enacted comprehensive tax legislation on December 22, 2017, which is commonly referred to as the Tax Cuts and Jobs Act ("TCJA"). The TCJA significantly revised the U.S. corporate income tax regime by, among other things, lowering the U.S. corporate tax rate from 35% to 21% effective January 1, 2018. The TCJA also repealed the deduction for domestic production activities, limited the deductibility of certain executive compensation, and implemented a modified territorial tax system with the introduction of the Global Intangible Low-Taxed Income (“GILTI”) tax rules. The TCJA also imposes a one-time transition tax on deemed repatriation of historical earnings of foreign subsidiaries. As a Subchapter “S” corporation the TCJA had a limited effect on the Company’s 2018 effective tax rate. The Company calculated that as a “C” corporation in 2019, the provisions of TCJA, except for the statutory rate, will not have a material impact on the income tax provision. Under GAAP, the Company is allowed to make an accounting policy election of either: (i) treating taxes due on future U.S. inclusions in taxable income related to GILTI as a current-period expense when incurred (the “period cost ” method); or (ii) factoring such amounts into the Company’s measurement of its deferred taxes (the “deferred” method). For taxable income inclusions due to the GILTI tax rules, the Company has elected the period cost method and has included the impact in the estimated annual effective tax rate as of September 30, 2019. As of September 30, 2019, the Company’s deferred tax assets included a valuation allowance of $18.1 million primarily related to foreign net operating loss carryforwards, foreign tax credit carryforwards, and capital losses that the Company determined are not more likely than not to be realized. The factors used to assess the likelihood of realization were the past performance of the related entities, forecasts of future taxable income, future reversals of existing taxable temporary differences, and available tax planning strategies that could be implemented to realize the deferred tax assets. The ability or failure to achieve the forecasted taxable income in these entities could affect the ultimate realization of deferred tax assets. As of December 31,2018 and September 30, 2019, the liability for income taxes associated with uncertain tax positions was $9.9 million and $14.6 million, respectively. Management believes it is unlikely that the liability for unrecognized tax benefits related to existing matters would increase or decrease within the next 12 months by a material amount. The Company is routinely subject to tax audit in several jurisdictions. Although adjustments could result from these audits, the Company is not aware of any issue that would materially change the liability for uncertain tax positions.

Commitment and Contingencies

Commitment and Contingencies	9 Months Ended
	Sep. 30, 2019
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	1 3 . The Company is subject to certain lawsuits, claims and assessments that arise in the ordinary course of business. Additionally, the Company has been named as a defendant in lawsuits alleging personal injuries as a result of contact with asbestos products at various project sites. Management believes that any significant costs relating to these claims will be reimbursed by applicable insurance and, although there can be no assurance that these matters will be resolved favorably, management believes that the ultimate resolution of any of these claims will not have a material adverse effect on our consolidated financial position, results of operations, or cash flows. A liability is recorded when it is both probable that a loss has been incurred and the amount of loss or range of loss can be reasonably estimated. When using a range of loss estimate, the Company records the liability using the low end of the range. The Company records a corresponding receivable for costs covered under its insurance policies. Management judgment is required to determine the outcome and the estimated amount of a loss related to such matters. Management believes that there are no claims or assessments outstanding which would materially affect the consolidated results of operations or the Company’s financial position. On or about March 1, 2017, the Peninsula Corridor Joint Powers Board, or the JPB, filed a lawsuit against Parsons Transportation Group, Inc., or PTG, in the Superior Court of California, County of San Mateo, in connection with a positive train control project on which PTG was engaged prior to termination of its contract by the JPB. PTG had previously filed a lawsuit against the JPB for breach of contract and wrongful termination. The JPB seeks damages in excess of $100.0 million, which the Company is currently disputing. In addition to filing a complaint for breach of contract and wrongful termination, the Company has denied the allegations raised by the JPB and, accordingly, filed affirmative defenses. The Company is currently defending against the JPB’s claims and the parties are still engaged in discovery. The Company also has a professional liability insurance policy to the extent the JPB proves any errors or omissions occurred. At this time, we are unable to determine the probability of the outcome of the litigation or determine a potential range of loss, if any. The Company has also filed a third-party claim against a subcontractor for indemnification in connection with this matter. In September 2015, a former Parsons employee filed an action in the United States District Court for the Northern District of Alabama against us as a qui tam relator on behalf of the United States (the “Relator”) alleging violation of the False Claims Act. The United States government did not intervene in this matter as it is allowed to do so under the statute. The Company filed a motion to dismiss the lawsuit on the grounds that the Relator did not meet the applicable statute of limitations. The District Court granted the motion to dismiss. The Relator’s attorney appealed the decision to the United States Court of Appeals of the Eleventh Circuit, which ultimately ruled in favor of the Relator, and the Company petitioned the United States Supreme Court to review the decision. The Supreme Court reviewed the decision and accepted the position of the Relator. The case was thus remanded to the United States District Court for the Northern District of Alabama. The defendants, including Parsons, will file appropriate pleadings opposing the allegations. At this time, we are unable to determine the probability of the outcome of the litigation or determine a potential range of loss, if any. Federal government contracts are subject to audits, which are performed for the most part by the Defense Contract Audit Agency (“DCAA”). Audits by the DCAA and other agencies consist of reviews of our overhead rates, operating systems and cost proposals to ensure that we account for such costs in accordance with the Cost Accounting Standards (“CAS”). If the DCAA determines we have not accounted for such costs in accordance with the CAS, the DCAA may disallow these costs. The disallowance of such costs may result in a reduction of revenue and additional liability for the Company. Historically, the Company has not experienced any material disallowed costs as a result of government audits. However, the Company can provide no assurance that the DCAA or other government audits will not result in material disallowances for incurred costs in the future. All audits of costs incurred on work performed through 2010 have been closed, and years thereafter remain open. Although there can be no assurance that these matters will be resolved favorably, management believes that their ultimate resolution will not have a material adverse impact on the Company’s consolidated financial position, results of operations, or cash flows.

Retirement and Other Benefit Pl

Retirement and Other Benefit Plans	9 Months Ended
	Sep. 30, 2019
Compensation And Retirement Disclosure [Abstract]
Retirement and Other Benefit Plans	1 4 . The Company’s principal retirement benefit plan is the Parsons Employee Stock Ownership Plan (“ESOP”), a stock bonus plan, established in 1975 to cover eligible employees of the Company and certain affiliated companies. Contributions of treasury stock to the ESOP are made annually in amounts determined by the Company’s board of directors and are held in trust for the sole benefit of the participants. Shares allocated to a participant’s account are fully vested after six years of credited service, or in the event(s) of reaching age 65, death or disability while an active employee of the Company. All of the Company’s common stock was acquired by the ESOP in conjunction with a reorganization in 1984, which was financed by the Company. Upon retirement, death, termination due to permanent disability, a severe financial hardship, conflict of interest or the exercise of diversification rights, participants’ interests in their ESOP accounts are redeemable at the current price per share of the stock. There is a lock-up agreement in place through November 3, 2019 affecting the ability of the ESOP Trustee to trade shares of the Company’s stock. During the lock-up period, the Trustee will redeem eligible participants’ interests in their ESOP accounts for cash, funded by the May 10, 2019 IPO Dividend described below. If that cash is exhausted before the end of the lock-up period, participants will put their shares to the Company which will redeem them for cash. Upon the expiration of the lock-up period, all shares held by the ESOP will be redeemable by participants in shares of the Company’s stock once vesting and eligibility requirements have been met. The Company presents all shares held by the ESOP as temporary equity on the consolidated balance sheets at their redemption value. The Company elected the policy to adjust the temporary equity balance to the maximum redemption amount at each balance sheet date for units that are not currently redeemable. Accordingly, at each balance sheet date, the Company will adjust the temporary equity balance to its maximum redemption amount with a corresponding offset to retained earnings. Total ESOP contribution expense was $11.4 million and $12.3 million for the three months ended September 28, 2018 and September 30, 2019, respectively, and $34.1 million and $36.8 million for the nine months ended September 28, 2018 and September 30, 2019, respectively. The expense is recorded in “Direct costs of contracts” and “Indirect, general and administrative expense” in the consolidated statements of income. The fiscal 2019 ESOP contribution has not yet been made. The amount is currently included in accrued liabilities. At December 31, 2018 and September 30, 2019, 78,172,809 shares and 78,138,602 shares of the Company’s stock were held by the ESOP which the Company recorded at their aggregate redemption value of $1.9 billion and $2.6 billion, respectively. On April 3, 2019, the board of directors of the Company declared a cash dividend to the Company’s sole existing shareholder at that time, the ESOP, in the amount of $2.00 per share, or $52.1 million in the aggregate (the “IPO Dividend”). The IPO Dividend was paid on May 10, 2019. On April 15, 2019, the board of directors of the Company declared a common stock dividend in a ratio of two shares of common stock for every one share of common stock then held by the Company’s shareholder (the “Stock Dividend”). The record date of the Stock Dividend was May 7, 2019, the day immediately prior to the consummation of the Company’s IPO on May 8, 2019, and the payment date of the Stock Dividend was May 8, 2019. Purchasers of the Company’s common stock in the Company’s public offering were not entitled to receive any portion of the Stock Dividend. During the year ended December 31, 2018, the Company did not declare any dividends. Please see the Company’s As part of an acquisition in 2014, the Company acquired a defined contribution pension plan, a defined benefit pension plan, and supplemental retirement plan. For the defined contribution pension plan, the Company contributes a base amount plus an additional amount based upon a predetermined formula. At December 31, 2018 and September 30, 2019, the defined benefit pension plan was in a net asset position of $1.7 million and $1.7 million, respectively, which is recorded in “Other noncurrent assets” on the consolidated balance sheets.

Investments in and Advances to

Investments in and Advances to Joint Ventures	9 Months Ended
	Sep. 30, 2019
Equity Method Investments And Joint Ventures [Abstract]
Investments in and Advances to Joint Ventures	1 5 . The Company participates in joint ventures to bid, negotiate and complete specific projects. The Company is required to consolidate these joint ventures if it holds the majority voting interest or if the Company meets the criteria under the consolidation model, as described below. The Company performs an analysis to determine whether its variable interests give the Company a controlling financial interest in a Variable Interest Entity (“VIE”) for which the Company is the primary beneficiary and should, therefore, be consolidated. Such analysis requires the Company to assess whether it has the power to direct the activities of the VIE and the obligation to absorb losses or the right to receive benefits that could potentially be significant to the VIE. The Company analyzed all of its joint ventures and classified them into two groups: (1) joint ventures that must be consolidated because they are either not VIEs and the Company holds the majority voting interest, or because they are VIEs and the Company is the primary beneficiary; and (2) joint ventures that do not need to be consolidated because they are either not VIEs and the Company holds a minority voting interest, or because they are VIEs and the Company is not the primary beneficiary. Many of the Company’s joint venture agreements provide for capital calls to fund operations, as necessary; however, such funding is infrequent and is not anticipated to be material. Letters of credit outstanding described in “Note 11 – Debt and Credit Facilities” that relate to project ventures are $76.8 million and $72.4 million at December 31, 2018 and September 30, 2019, respectively. In the table below, aggregated financial information relating to the Company’s joint ventures is provided because their nature, risk and reward characteristics are similar. None of the Company’s current joint ventures that meet the characteristics of a VIE are individually significant to the consolidated financial statements. Consolidated Joint Ventures The following represents financial information for consolidated joint ventures included in the consolidated financial statements (in thousands): December 31, 2018 September 30, 2019 Current assets $ 287,227 $ 254,204 Noncurrent assets 2,689 2,836 Total assets 289,916 257,040 Current liabilities 199,833 198,079 Total liabilities 199,833 198,079 Total joint venture equity $ 90,083 $ 58,961 Three Months Ended Nine Months Ended September 28, 2018 September 30, 2019 September 28, 2018 September 30, 2019 Revenue $ 126,480 $ 117,611 $ 413,548 $ 341,719 Costs 116,468 108,839 262,146 322,826 Net income $ 10,012 $ 8,772 $ 151,402 $ 18,893 Net income attributable to noncontrolling interests $ 4,844 $ 4,481 $ 10,316 $ 8,012 The assets of the consolidated joint ventures are restricted for use only by the particular joint venture and are not available for the Company’s general operations. Unconsolidated Joint Ventures The Company accounts for its unconsolidated joint ventures using the equity method of accounting. Under this method, the Company recognizes its proportionate share of the net earnings of these joint ventures as “Equity in earnings (loss) of unconsolidated joint ventures” in the consolidated statements of income. The Company’s maximum exposure to loss as a result of its investments in unconsolidated VIEs is typically limited to the aggregate of the carrying value of the investment and future funding commitments. The following represents the financial information of the Company’s unconsolidated joint ventures as presented in their unaudited financial statements (in thousands): December 31, 2018 September 30, 2019 Current assets $ 707,457 $ 778,876 Noncurrent assets 876,385 956,367 Total assets 1,583,842 1,735,243 Current liabilities 560,306 625,949 Noncurrent liabilities 813,269 895,514 Total liabilities 1,373,575 1,521,463 Total joint venture equity 210,267 213,780 Investments in and advances to unconsolidated joint ventures $ 63,560 $ 66,584 Three Months Ended Nine Months Ended September 28, 2018 September 30, 2019 September 28, 2018 September 30, 2019 Revenue $ 482,634 $ 474,600 $ 1,234,946 $ 1,225,284 Costs 462,042 452,001 1,186,184 1,166,008 Net income $ 20,592 $ 22,599 $ 48,762 $ 59,276 Equity in earnings of unconsolidated joint ventures $ 12,707 $ 7,274 $ 25,577 $ 29,305 The Company received net distributions from (made contributions to) its unconsolidated joint ventures for the three months ended September 28, 2018 and September 30, 2019 of $20.1 million and $13.7 million, respectively, and $28.6 million and $28.0 million for the nine months ended September 28, 2018 and September 30, 2019, respectively.

Related Party Transactions

Related Party Transactions	9 Months Ended
	Sep. 30, 2019
Related Party Transactions [Abstract]
Related Party Transactions	1 6 . The Company often provides services to unconsolidated joint ventures and revenues include amounts related to recovering overhead costs for these services. Revenues related to services the Company provided to unconsolidated joint ventures for the three months ended September 28, 2018 and September 30, 2019, were $36.6 million and $28.8 million December 31, 2018 September 30, 2019 Accounts receivable $ 38,742 $ 44,637 Contract assets 2,648 2,734 Contract liabilities $ 10,861 $ 5,517

Fair Value of Financial Instrum

Fair Value of Financial Instruments	9 Months Ended
	Sep. 30, 2019
Fair Value Disclosures [Abstract]
Fair Value of Financial Instruments	1 7 . The authoritative guidance on fair value measurement defines fair value as the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date (referred to as an “exit price”). At December 31, 2018 and September 30, 2019, the Company’s financial instruments include cash, cash equivalents, accounts receivable, accounts payable, and other liabilities. The fair values of these financial instruments approximate their carrying values due to their short-term maturities. Investments measured at fair value are based on one or more of the following three valuation techniques: • Market approach —Prices and other relevant information generated by market transactions involving identical or comparable assets or liabilities; • Cost approach —Amount that would be required to replace the service capacity of an asset (i.e., replacement cost); and • Income approach —Techniques to convert future amounts to a single present amount based on market expectations (including present value techniques, option-pricing models and lattice models). In addition, the guidance establishes a fair value hierarchy that prioritizes the inputs to valuation techniques used to measure fair value. The hierarchy gives the highest priority to unadjusted quoted market prices in active markets for identical assets and liabilities (Level 1 measurements) and the lowest priority to unobservable inputs (Level 3 measurements). The three levels of the fair value hierarchy are: Level 1 Unadjusted quoted prices in active markets that are accessible at the measurement date for identical assets and liabilities; Level 2 Pricing inputs that include quoted prices for similar assets and liabilities in active markets and inputs that are observable for the asset or liability, either directly or indirectly, for substantially the full term of the instrument; and Level 3 Prices or valuations that require inputs that are both significant to the fair value measurements and unobservable. The methods described above may produce a fair value calculation that may not be indicative of net realizable value or reflective of future fair values. Furthermore, while the Company believes its valuation methods are appropriate and consistent with other market participants, the use of different methodologies or assumptions to determine the fair value of certain financial instruments could result in a different fair value measurement at the reporting date. The following table sets forth assets associated with the pension plan in “Note 14 – Retirement and Other Benefit Plans” that are accounted for at fair value by Level within the fair value hierarchy. Fair value as of December 31, 2018 (in thousands): Level 1 Level 2 Level 3 Total Mutual funds $ 2,539 $ - $ - $ 2,539 Fixed income - 10,168 - 10,168 Cash and cash equivalents 361 - - 361 $ 2,900 $ 10,168 $ - $ 13,068 Fair value as of September 30, 2019 (in thousands): Level 1 Level 2 Level 3 Total Mutual funds $ 2,888 $ - $ - $ 2,888 Fixed income - 10,579 - 10,579 Cash and cash equivalents 294 - - 294 $ 3,182 $ 10,579 $ - $ 13,761 As described in “Note 14 – Retirement and Other Benefit Plans,” the Company acquired a defined contribution pension plan, a defined benefit pension plan, and supplemental retirement plans. At December 31, 2018 and September 30, 2019, the Company measured the mutual funds held within the defined benefit pension plan at fair value using unadjusted quoted prices in active markets that are accessible for identical assets. The Company measured the fixed income securities using market bid and ask prices. The inputs that are significant to valuation of fixed income securities are generally observable and therefore have been classified as Level 2. The following table sets forth redeemable common stock associated with the ESOP in as described in “Note 14 – Retirement and Other Benefit Plans” that is accounted for at fair value by Level within the fair value hierarchy. Fair value as of December 31, 2018 (in thousands): Level 1 Level 2 Level 3 Total Redeemable common stock $ - $ - $ 1,876,309 $ 1,876,309 Fair value as of September 30, 2019 (in thousands): Level 1 Level 2 Level 3 Total Redeemable common stock $ 2,577,011 $ - $ - $ 2,577,011 As described in “Note 14 – Retirement and Other Benefit Plans,” the Company is obligated to redeem eligible participants’ interests in their ESOP accounts for cash upon an employee’s election. All shares held by the ESOP are eventually redeemable in the future for cash at the option of the holder once vesting and eligibility requirements have been met. The Company presents all shares held by the ESOP as temporary equity on the consolidated balance sheets at their redemption value. At December 31, 2018 and September 30, 2019, 78,172,809 shares and 78,138,602 shares, respectively, of the Company’s stock were held by the ESOP which the Company recorded at their aggregate redemption values of $1.9 billion and $2.6 billion, respectively. The following tables present a reconciliation of the beginning and ending balances of the fair value measurements using significant unobservable inputs (Level 3) (in thousands): Balance at December 31, 2018 $ 1,876,309 Transfer to Level 1 (1,876,309 ) Balance at September 30, 2019 $ -

Earnings Per Share

Earnings Per Share	9 Months Ended
	Sep. 30, 2019
Earnings Per Share [Abstract]
Earnings Per Share	1 8 . Basic earnings per common share is computed using the weighted average number of shares outstanding during the period and income available to shareholders. Diluted earnings per share (“EPS”) is computed similar to basic EPS, except the weighted average number of shares outstanding is increased to include the dilutive effects of outstanding stock options and other stock-based awards. There were no dilutive securities outstanding for the three and nine months ended September 28, 2018 and September 30, 2019. The weighted average number of shares used to compute basic and diluted EPS were: Three Months Ended Nine Months Ended September 28, 2018 September 30, 2019 September 28, 2018 September 30, 2019 Basic weighted average number of shares outstanding 79,185,527 99,434,877 80,702,032 89,977,493 Dilutive common share equivalents - - - - Diluted weighted average number of shares outstanding 79,185,527 99,434,877 80,702,032 89,977,493

Segment Information

Segment Information	9 Months Ended
	Sep. 30, 2019
Segment Reporting [Abstract]
Segment Information	19 . The Company operates in two reportable segments: Federal Solutions and Critical Infrastructure. The Federal Solutions segment provides advanced technical solutions to the U.S. government, delivering timely, cost-effective hardware, software and services for mission-critical projects. The segment provides advanced technologies, supporting national security missions in cybersecurity, missile defense, and military facility modernization, logistics support, hazardous material remediation and engineering services. The Critical Infrastructure segment provides integrated engineering and management services for complex physical and digital infrastructure around the globe. The Critical Infrastructure segment is a technology innovator focused on next generation digital systems and complex structures. Industry leading capabilities in engineering and project management allow the Company to deliver significant value to customers by employing cutting-edge technologies, improving timelines and reducing costs. The Company defines its reportable segments based on the way the chief operating decision maker (“CODM”), currently its Chairman and Chief Executive Officer, evaluates the performance of each segment and manages the operations of the Company for purposes of allocating resources among the segments. The CODM evaluates segment operating performance using segment Revenue and segment Adjusted EBITDA attributable to Parsons Corporation. The following table summarizes business segment revenue for the periods presented (in thousands): Three Months Ended Nine Months Ended September 28, 2018 September 30, 2019 September 28, 2018 September 30, 2019 Federal Solutions revenue $ 443,725 $ 486,175 $ 1,076,125 $ 1,387,484 Critical Infrastructure revenue 532,432 537,102 1,555,443 1,529,940 Total revenue $ 976,157 $ 1,023,277 $ 2,631,568 $ 2,917,424 The Company defines Adjusted EBITDA attributable to Parsons Corporation as Adjusted EBITDA excluding Adjusted EBITDA attributable to noncontrolling interests. The Company defines Adjusted EBITDA as net income (loss) attributable to Parsons Corporation, adjusted to include net income (loss) attributable to noncontrolling interests and to exclude interest expense (net of interest income), provision for income taxes, depreciation and amortization and certain other items that are not considered in the evaluation of ongoing operating performance. These other items include net income (loss) attributable to noncontrolling interests, asset impairment charges, income and expense recognized on litigation matters, expenses incurred in connection with acquisitions and other non-recurring transaction costs and expenses related to our prior restructuring. The following table reconciles business segment Adjusted EBITDA attributable to Parsons Corporation to Net Income attributable to Parsons Corporation for the periods presented (in thousands): Three Months Ended Nine Months Ended Adjusted EBITDA attributable to Parsons Corporation September 28, 2018 September 30, 2019 September 28, 2018 September 30, 2019 Federal Solutions $ 45,556 $ 50,359 $ 101,052 $ 126,658 Critical Infrastructure 38,006 33,976 80,296 102,177 Adjusted EBITDA attributable to Parsons Corporation 83,562 84,335 181,348 228,835 Adjusted EBITDA attributable to noncontrolling interests 5,002 4,655 10,681 8,384 Depreciation and amortization (23,599 ) (31,027 ) (46,656 ) (92,692 ) Interest expense, net (5,589 ) (4,482 ) (12,117 ) (18,448 ) Income tax (expense) benefit (4,154 ) 15,453 (18,526 ) 67,063 Litigation-related gains(a) - - 129,674 - Amortization of deferred gain resulting from sale-leaseback transactions(b) 1,798 - 5,440 - Equity-based compensation (5,049 ) 1,657 (13,198 ) (45,504 ) Transaction-related costs(c) (2,456 ) (9,891 ) (7,511 ) (26,961 ) Restructuring(d) - (309 ) - (2,880 ) Other(e) (3,449 ) 902 (3,929 ) (2,973 ) Net income including noncontrolling interests 46,066 61,293 225,206 114,824 Net income attributable to noncontrolling interests 4,844 4,481 10,316 8,012 Net income attributable to Parsons Corporation $ 41,222 $ 56,812 $ 214,890 $ 106,812 (a) Reversal of an accrued liability, with $55.1 million recorded to revenue and $74.6 million recorded to other income (“gain associated with claim on long-term contract”) in results of operations, associated with a lawsuit against a joint venture in which the Company is the managing partner. Please see “Note 14 – Commitments and Contingencies” in the Company’s Form S-1/A filed on April 29, 2019, for a description of this matter, which was resolved in favor of the Company on June 13, 2018 (b) Reflects recognized deferred gains related to sales-leaseback transactions described in “Note 10 – Sale-Leasebacks.” ( c ) Reflects costs incurred in connection with acquisitions, the IPO, and other non-recurring transaction costs, primarily fees paid for professional services and employee retention. ( d ) Reflects costs associated with corporate restructuring initiatives. ( e ) Includes a combination of gain/loss related to sale of fixed assets, software implementation costs, and other individually insignificant items that are non-recurring in nature. Asset information by segment is not a key measure of performance used by the CODM. The following tables presents revenues and property and equipment, net by geographic area (in thousands): Three Months Ended Nine Months Ended September 28, 2018 September 30, 2019 September 28, 2018 September 30, 2019 Revenue North America $ 805,320 $ 849,839 $ 2,131,562 $ 2,400,124 Middle East 164,677 169,028 485,377 504,604 Rest of World 6,160 4,410 14,629 12,696 Total Revenue $ 976,157 $ 1,023,277 $ 2,631,568 $ 2,917,424 The geographic location of revenue is determined by the location of the customer. The prior reporting of revenue by geographic location has been conformed to the current presentation. December 31, 2018 September 30, 2019 Property and Equipment, Net North America $ 86,847 $ 103,690 Middle East 5,002 5,548 Total Property and Equipment, Net $ 91,849 $ 109,238 North America includes revenue in the United States for the three months ended September 28, 2018 and September 30, 2019 of $747.7 million and $774.2 million, respectively, and for the nine months ended September 28, 2018 and September 30, 2019, $2.0 billion and $2.2 billion, respectively. North America property and equipment, net includes $79.9 million and $97.3 million of property and equipment, net in the United States at December 31, 2018 and September 30, 2019, respectively. The following table presents revenues by business lines (in thousands): Three Months Ended Nine Months Ended September 28, 2018 September 30, 2019 September 28, 2018 September 30, 2019 Revenue Cyber & Intelligence $ 68,895 $ 90,429 $ 177,838 $ 247,710 Defense 133,259 144,160 297,318 425,603 Mission Solutions 122,780 87,936 280,902 237,914 Engineered Systems 118,791 129,989 320,067 367,542 Geospatial - 33,661 - 108,715 Federal Solutions revenues 443,725 486,175 1,076,125 1,387,484 Connected Communities 165,529 151,779 491,444 459,277 Mobility Solutions 300,523 286,199 894,796 836,779 Industrial 66,380 99,124 169,203 233,884 Critical Infrastructure revenues 532,432 537,102 1,555,443 1,529,940 Total Revenue $ 976,157 $ 1,023,277 $ 2,631,568 $ 2,917,424 Revenue for the three and nine months ended September 28, 2018 included $55.1 million related to the settlement of a claim that was resolved in favor of the Company in the Mobility Solutions business line of our Critical Infrastructure segment. Please see “Note 14 – Commitments and Contingencies”

Subsequent Events

Subsequent Events	9 Months Ended
	Sep. 30, 2019
Subsequent Events [Abstract]
Subsequent Events	2 0 . On October 14, 2019, the Board of Directors of the Company approved the repurchase by the Company of shares of its Common Stock pursuant to the Company’s ESOP. The ESOP provides that, if, prior to the expiration of the lock-up period in connection with the Company’s initial public offering, the trust administering the ESOP has insufficient cash to fund all requested distributions, then, with respect to any distribution election received after the date the ESOP trustee determines it will no longer have sufficient cash to fund all requested distributions during the lock-up period, and provides at least 10 business days' written notice to the Company of such determination, the Company shall automatically, and without further action by the Company or the ESOP trustee, repurchase such number of shares of the Company's Common Stock held by the trust as is subject to any such election. The Company repurchased approximately 157,100 shares of its Common Stock for approximately $5.4 million. Pursuant to expiration of the lock-up period, the ESOP will commence regular distributions of shares to brokerage accounts of retired participants who have met the requirements for distribution.

Basis of Presentation and Pri_2

Basis of Presentation and Principles of Consolidation (Policies)	9 Months Ended
	Sep. 30, 2019
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Accumulated Deficit	Accumulated Deficit The Company's accounting policy is to record dividends and accretion of redeemable stock as a reduction of retained earnings. In the absence of retained earnings, the Company will charge the dividends and/or accretion of redeemable stock to Additional Paid-in Capital
Fiscal Periods	Fiscal Periods In October 2018, our board of directors approved a change in our annual and quarterly fiscal period ends from the last Friday on or before the calendar year or quarterly month-end to the last day of the calendar year or quarterly month-end. Accordingly, the period end for the first, second, and third quarters of fiscal 2018 and fiscal 2019 are March 30, 2018, June 29, 2018, and September 28, 2018, respectively, and March 31, 2019, June 30, 2019, and September 30, 2019, respectively. The number of days in the three- and nine-month periods ended September 28, 2018 and September 30, 2019 were 91 and 273, respectively, and 92 and 273, respectively.
Use of Estimates	Use of Estimates The preparation of the consolidated financial statements in accordance with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Actual amounts could differ from those estimates. The Company’s most significant estimates and judgments involve revenue recognition with respect to the determination of the costs to complete contracts and transaction price; determination of self-insurance reserves; valuation of the Company’s fair value of common stock (for periods prior to the IPO); useful lives of property and equipment and intangible assets; calculation of allowance for doubtful accounts; valuation of deferred income tax assets and uncertain tax positions, among others. Please see “Note 2 – Summary of Significant Accounting Policies” of Notes to Consolidated Financial Statements included in the Company’s Form S-1/A filed April 29, 2019, for a discussion of the significant estimates and assumptions affecting our consolidated financial statements. Estimates of costs to complete contracts are continually evaluated as work progresses and are revised when necessary. When a change in estimate is determined to have an impact on contract profit, the Company records a positive or negative adjustment to the consolidated statement of income.
Inventory	Inventory Included in Prepaid expenses and other current assets
Redeemable Common Stock	Redeemable Common Stock In connection with the Company’s IPO on May 8, 2019, all Employee Stock Ownership Plan (“ESOP”) shares were contingently redeemable for cash during the 180-day lock-up period which ended on November 3, 2019. During the 180-day lock-up period, the Company presented all shares held by the ESOP as temporary equity on the consolidated balance sheets as Redeemable common stock held by Employee Stock Ownership Plan (ESOP)
Leases	Leases In February 2016, the FASB issued ASU 2016-02 “Leases (Topic 842)”, which is a new standard related to leases to increase transparency and comparability among organizations by requiring the recognition of right-of-use (“ROU”) assets obtained in exchange for lease liabilities on the balance sheet. Most prominent among the changes in the standard is the recognition of ROU assets and lease liabilities by lessees for those leases classified as operating leases. Under the standard, disclosures are required to meet the objective of enabling users of financial statements to assess the amount, timing, and uncertainty of cash flows arising from leases. The Company elected to adopt the standard, and available practical expedients, effective January 1, 2019. These practical expedients allowed the Company to keep the lease classification assessed under the previous lease accounting standard (ASC 840) without reassessment under the new standard, and allowed all separate lease components, including non-lease components, to be accounted for as a single lease component for all existing leases prior to adoption of the new standard. Furthermore, the Company made an accounting policy election to not recognize a lease liability and ROU asset for leases with lease terms of twelve months or less. The Company adopted this new standard under the modified retrospective transition approach without adjusting comparative periods in the financial statements, as allowed under Topic 842, and implemented internal controls and key system functionality to enable the preparation of financial information on adoption. The standard had a material impact on the Company’s consolidated balance sheets but did not have an impact on the consolidated income statements. The most significant impact was the recognition of ROU assets and lease liabilities for operating leases, while accounting for finance leases remained substantially unchanged. As a result of the adoption, the Company recorded a cumulative-effect adjustment to retained earnings of $52.6 million net of deferred tax asset adjustment of $0.7 million, representing the unamortized portion of a deferred gain previously recorded as a sale-leaseback transaction associated with the sale of an office building in 2011. The Company concluded the transaction resulted in the transfer of control of the office building to the buyer-lessor at market terms and would have qualified as a sale under Topic 842 with gain recognition in the period the sale was recognized. The Company determines if an arrangement is a lease at inception. Operating leases are included in operating lease ROU assets and current and long-term operating lease liabilities in the consolidated balance sheets. Finance leases are included in other noncurrent assets, accrued expenses and other current liabilities and other long-term liabilities in the consolidated balance sheets. ROU assets represent the Company’s right to use an underlying asset for the lease term and lease liabilities represent our obligation to make lease payments arising from the lease. Operating lease ROU assets and liabilities are recognized at commencement date based on the present value of lease payments over the lease term. As most of the Company’s leases do not provide an implicit rate, incremental borrowing rates are used based on the information available at commencement date in determining the present value of lease payments. The operating lease ROU asset also includes any lease payments made and excludes lease incentives. Lease terms may include options to extend or terminate the lease when it is reasonably certain that we will exercise that option. Lease expense for operating lease payments is recognized on a straight-line basis over the lease term. We have lease agreements with lease and non-lease components, which are generally accounted for separately. For certain equipment leases, such as vehicles, we account for the lease and non-lease components as a single lease component. Additionally, for certain equipment leases, we apply a portfolio approach to effectively account for the operating lease ROU assets and liabilities. The Company has operating and finance leases for corporate and project office spaces, vehicles, heavy machinery and office equipment. Our leases have remaining lease terms of one year to 10 years, some of which may include options to extend the leases for up to five years, and some of which may include options to terminate the leases up to the seventh year. As of September 30, 2019, assets recorded under finance leases were $1.8 million

Acquisitions (Tables)

Acquisitions (Tables)	9 Months Ended
	Sep. 30, 2019
Polaris Alpha
Summary of Estimated Fair Values of Assets Acquired and Liabilities Assumed on Preliminary Purchase Price Allocation	The following table summarizes the estimated fair values of the assets acquired and liabilities assumed (in thousands): Amount Cash and cash equivalents $ 7,914 Accounts receivable 29,688 Contract assets 35,229 Prepaid expenses and other current assets 9,295 Property and equipment 9,024 Goodwill 243,471 Intangible assets 199,520 Other noncurrent assets 2,203 Accounts payable (13,942 ) Accrued expenses and other current liabilities (26,419 ) Contract liabilities (3,529 ) Deferred tax liabilities (2,231 ) Other long-term liabilities (1,146 ) Net assets acquired $ 489,077
Schedule of Intangible Assets Value on Purchase Price	Of the total purchase price, the following values were assigned to intangible assets (in thousands, except for years): Gross Carrying Amount Amortization Period (in years) Developed technology $ 84,900 4 Customer relationships 76,000 8 Backlog 34,900 2 Trade name 3,600 1 Leases $ 120 6
Schedule of Supplemental Pro Forma Information	Supplemental information on an unaudited pro forma operating results assuming the Polaris Alpha acquisition had been consummated as of the beginning of fiscal year 2018 (December 31, 2017) (in thousands) is as follows: Three Months Ended Nine Months Ended September 28, 2018 September 28, 2018 Pro forma revenue $ 976,157 $ 2,784,864 Pro forma net income including noncontrolling interests $ 46,848 $ 179,071
OGSystems
Summary of Estimated Fair Values of Assets Acquired and Liabilities Assumed on Preliminary Purchase Price Allocation	The following table summarizes the estimated fair values of the assets acquired and liabilities assumed based on the preliminary purchase price allocation as of the date of acquisition (in thousands): Amount Cash and cash equivalents $ 5,772 Accounts receivable 9,904 Contract assets 9,747 Prepaid expenses and other current assets 4,307 Property and equipment 4,085 Right of use assets, operating leases 8,826 Goodwill 183,540 Intangible assets 92,300 Other noncurrent assets 10 Accounts payable (5,450 ) Accrued expenses and other current liabilities (7,147 ) Contract liabilities (1,300 ) Short-term lease liabilities, operating leases (805 ) Income tax payable (1,469 ) Deferred tax liabilities (904 ) Long-term lease liabilities, operating leases (8,021 ) Other long-term liabilities (1,015 ) Net assets acquired $ 292,380
Schedule of Intangible Assets Value on Purchase Price	Of the total purchase price, the following values were assigned to intangible assets (in thousands, except for years): Gross Carrying Amount Amortization Period (in years) Customer relationships $ 57,100 5 Backlog 27,700 3 Trade name 3,800 2 Non-compete agreements 2,400 3 Developed technologies $ 1,300 3
Schedule of Supplemental Pro Forma Information	Supplemental information on an unaudited pro forma operating results assuming the OGSystems acquisition had been consummated as of the beginning of fiscal year 2018 (December 31, 2017) (in thousands) is as follows: Three Months Ended Nine Months Ended September 28, 2018 September 30, 2019 September 28, 2018 September 30, 2019 Pro forma revenue $ 1,007,793 $ 1,023,277 $ 2,715,572 $ 2,919,379 Pro forma net income including noncontrolling interests $ 39,224 $ 61,293 $ 196,905 $ 118,896
QRC Technologies
Summary of Estimated Fair Values of Assets Acquired and Liabilities Assumed on Preliminary Purchase Price Allocation	The following table summarizes the estimated fair values of the assets acquired and liabilities assumed based on the preliminary purchase price allocation as of the date of acquisition (in thousands): Amount Cash and cash equivalents $ 5,925 Accounts receivable 5,587 Prepaid expenses and other current assets 5,467 Property and equipment 1,205 Right of use assets, operating leases 5,228 Goodwill 128,387 Intangible assets 72,900 Accounts payable (1,567 ) Accrued expenses and other current liabilities (3,771 ) Short-term lease liabilities, operating leases (545 ) Long-term lease liabilities, operating leases (4,683 ) Net assets acquired $ 214,133
Schedule of Intangible Assets Value on Purchase Price	Of the total purchase price, the following values were assigned to intangible assets (in thousands, except for years): Gross Carrying Amount Amortization Period (in years) Customer relationships $ 47,600 12 Backlog 700 1 Trade name 800 2 Non-compete agreements 1,200 4 Developed technologies $ 22,600 3-5
Schedule of Supplemental Pro Forma Information	Supplemental information on an unaudited pro forma operating results assuming the QRC Technologies acquisition had been consummated as of the beginning of fiscal year 2018 (December 31, 2017) (in thousands) is as follows: Three Months Ended Nine Months Ended September 28, 2018 September 30, 2019 September 28, 2018 September 30, 2019 Pro forma revenue $ 987,343 $ 1,026,831 $ 2,657,105 $ 2,938,973 Pro forma net income including noncontrolling interests $ 44,944 $ 65,782 $ 212,728 $ 117,399

Contracts with Customers (Table

Contracts with Customers (Tables)	9 Months Ended
	Sep. 30, 2019
Revenue From Contract With Customer [Abstract]
Summary of Disaggregation of Revenue	The Company’s contracts contain both fixed-price and cost reimbursable components. Contract types are based on the component that represents the majority of the contract. The following table presents revenue disaggregated by contract type (in thousands): Three Months Ended Nine Months Ended September 28, 2018 September 30, 2019 September 28, 2018 September 30, 2019 Fixed-Price $ 300,225 $ 288,316 $ 833,224 $ 850,658 Time-and-Materials 254,435 285,586 732,555 810,656 Cost-Plus 421,497 449,375 1,065,789 1,256,110 Total $ 976,157 $ 1,023,277 $ 2,631,568 $ 2,917,424
Summary of Contract Assets and Contract Liabilities	Contract assets and contract liabilities balances at December 31, 2018 and September 30, 2019 were as follows (in thousands): December 31, 2018 September 30, 2019 $ change % change Contract assets $ 515,319 $ 583,670 $ 68,351 13.3 % Contract liabilities 208,576 231,032 22,456 10.8 % Net contract assets (liabilities) (1) $ 306,743 $ 352,638 $ 45,895 15.0 % (1)
Summary of Changes in Contract Assets and Contract Liabilities	The changes in contract assets and contract liabilities were the result of normal business activity and not significantly impacted by other factors, except as follows: December 31, 2018 September 30, 2019 Acquired contract assets $ 35,229 $ 9,747 Acquired contract liabilities 3,529 1,300 Change in the estimate of variable consideration - 14,506 Reversal of provision for contract losses (1) $ 133,180 $ - (1) Reversal of provision for contract losses of $133.2 million, of which $55.1 million was recorded as an increase in revenue with the remainder recorded as other income.
Summary of Accounts Receivable, Net	Accounts receivable, net consisted of the following as of December 31, 2018 and September 30, 2019 (in thousands): December 31, 2018 September 30, 2019 Billed $ 538,808 $ 516,099 Unbilled 135,180 200,477 Total accounts receivable, gross 673,988 716,576 Allowance for doubtful accounts (50,702 ) (42,902 ) Total accounts receivable, net $ 623,286 $ 673,674
Summary of Remaining Unsatisfied Performance Obligations Expect to Satisfy	The Company expects to satisfy its RUPO as of September 30, 2019 over the following periods (in thousands): Period RUPO Will Be Satisfied Within One Year Within One to Two Years Thereafter Federal Solutions $ 1,198,634 $ 436,620 $ 208,734 Critical Infrastructure 1,636,525 960,469 643,170 Total $ 2,835,159 $ 1,397,089 $ 851,904

Leases (Tables)

Leases (Tables)	9 Months Ended
	Sep. 30, 2019
Leases [Abstract]
Summary of Lease Costs	The components of lease costs for the three and nine months ended September 30, 2019 are as follows (in thousands): Three Months Ended Nine Months Ended September 30, 2019 September 30, 2019 Operating lease cost $ 17,969 $ 53,835 Short-term lease cost 5,429 10,925 Amortization of right-of-use assets 120 455 Interest on lease liabilities 15 46 Sublease income (712 ) (2,727 ) Total lease cost $ 22,821 $ 62,534
Schedule of Supplemental Cash Flow Information Related to Leases	Supplemental cash flow information related to leases for the nine months ended September 30, 2019 is as follows (in thousands): Nine Months Ended September 30, 2019 Operating cash flows for operating leases $ 52,056 Operating cash flows for financing activities 570 Right-of-use assets obtained in exchange for new operating lease liabilities 274,212 Right-of-use assets obtained in exchange for new finance lease liabilities $ 1,818
Schedule of Supplemental Balance Sheet and Other Information Related to Leases	Supplemental balance sheet and other information related to leases as of September 30, 2019 is as follows (in thousands): September 30, 2019 Operating Leases: Right-of-use assets $ 219,207 Lease liabilities: Current $ 49,074 Long-term 188,571 Total operating lease liabilities $ 237,645 Finance Leases: Other noncurrent assets $ 1,362 Lease liabilities: Accrued expenses and other current liabilities $ 558 Other long-term liabilities 736 Total finance lease liabilities $ 1,294 Weighted Average Remaining Lease Term: Operating leases 6 years Finance leases 3 years Weighted Average Discount Rate: Operating leases 4.3 % Finance leases 4.4 %
Schedule of Maturity Analysis of Future Undiscounted Cash Flows	A maturity analysis of the future undiscounted cash flows associated with the Company’s operating and finance lease liabilities as of September 30, 2019 is as follows (in thousands): Operating Leases Finance Leases 2019 $ 15,409 $ 160 2020 54,561 574 2021 50,333 421 2022 44,160 187 2023 36,996 25 Thereafter 64,423 - Total lease payments 265,882 1,367 Less: imputed interest (28,237 ) (73 ) Total present value of lease liabilities $ 237,645 $ 1,294

Goodwill (Tables)

Goodwill (Tables)	9 Months Ended
	Sep. 30, 2019
Goodwill And Intangible Assets Disclosure [Abstract]
Summary of Changes in Carrying Value of Goodwill by Reporting Segment	The following table summarizes the changes in the carrying value of goodwill by reporting segment at December 31, 2018 and September 30, 2019 (in thousands): December 31, 2018 Acquisitions Foreign Exchange September 30, 2019 Federal Solutions $ 666,841 $ 311,860 $ - $ 978,701 Critical Infrastructure 70,097 - 1,279 71,376 Total $ 736,938 $ 311,860 $ 1,279 $ 1,050,077

Intangible Assets (Tables)

Intangible Assets (Tables)	9 Months Ended
	Sep. 30, 2019
Goodwill And Intangible Assets Disclosure [Abstract]
Schedule of Gross Amount and Accumulated Amortization of Intangible Assets	The gross amount and accumulated amortization of intangible assets with finite useful lives included in “Intangible assets, net” on the consolidated balance sheets are as follows (in thousands except for years): December 31, 2018 September 30, 2019 Weighted Average Gross Carrying Amount Accumulated Amortization Net Carrying Amount Gross Carrying Amount Accumulated Amortization Net Carrying Amount Amortization Period (in years) Backlog $ 80,754 $ (58,295 ) $ 22,459 $ 109,155 $ (80,321 ) $ 28,834 3 Customer relationships 121,629 (38,974 ) 82,655 226,329 (60,266 ) 166,063 7 Leases 670 (561 ) 109 670 (576 ) 94 5 Developed technology 87,839 (15,174 ) 72,665 111,739 (32,545 ) 79,194 4 Trade name 3,600 (2,100 ) 1,500 8,200 (5,092 ) 3,108 1 Non-compete agreements - - - 3,600 (650 ) 2,950 3 Other intangibles 275 (145 ) 130 1,076 (162 ) 914 10 Total intangible assets $ 294,767 $ (115,249 ) $ 179,518 $ 460,769 $ (179,612 ) $ 281,157
Schedule of Estimated Amortization Expense	Estimated amortization expense in each of the next five years and beyond is as follows (in thousands): September 30, 2019 2019 (remaining) $ 23,049 2020 83,511 2021 78,778 2022 34,517 2023 22,599 Thereafter 38,703 Total $ 281,157

Property and Equipment, Net (Ta

Property and Equipment, Net (Tables)	9 Months Ended
	Sep. 30, 2019
Property Plant And Equipment [Abstract]
Schedule of Property and equipment, net	Property and equipment consisted of the following at December 31, 2018 and September 30, 2019 (in thousands): December 31, 2018 September 30, 2019 Useful lives (years) Buildings and leasehold improvements $ 54,348 $ 71,698 1-15 Furniture and equipment 81,705 85,322 3-10 Computer systems and equipment 148,255 168,241 3-10 Construction equipment 12,074 11,753 5-7 Accumulated depreciation (204,533 ) (227,776 ) Property and equipment, net $ 91,849 $ 109,238

Debt and Credit Facilities (Tab

Debt and Credit Facilities (Tables)	9 Months Ended
	Sep. 30, 2019
Debt Disclosure [Abstract]
Schedule of Long Term Debt	Debt consisted of the following (in thousands): Long-Term: December 31, 2018 September 30, 2019 Revolving credit facility $ 180,000 $ - Senior notes 250,000 250,000 Debt issuance costs (836 ) (694 ) Total long-term $ 429,164 $ 249,306
Schedule of Aggregate Amount Debt Repayable	On July 1, 2014, the Company finalized a private placement whereby the Company raised an aggregate amount of $250.0 million in debt repayable as follows (in thousands): Tranche Debt Amount Maturity Date Interest Rates Senior Note, Series A $ 50,000 July 15, 2021 4.44 % Senior Note, Series B 100,000 July 15, 2024 4.98 % Senior Note, Series C 60,000 July 15, 2026 5.13 % Senior Note, Series D $ 40,000 July 15, 2029 5.38 %

Investments in and Advances t_2

Investments in and Advances to Joint Ventures (Tables)	9 Months Ended
	Sep. 30, 2019
Equity Method Investments And Joint Ventures [Abstract]
Summary of Financial Information for Consolidated Joint Ventures	The following represents financial information for consolidated joint ventures included in the consolidated financial statements (in thousands): December 31, 2018 September 30, 2019 Current assets $ 287,227 $ 254,204 Noncurrent assets 2,689 2,836 Total assets 289,916 257,040 Current liabilities 199,833 198,079 Total liabilities 199,833 198,079 Total joint venture equity $ 90,083 $ 58,961 Three Months Ended Nine Months Ended September 28, 2018 September 30, 2019 September 28, 2018 September 30, 2019 Revenue $ 126,480 $ 117,611 $ 413,548 $ 341,719 Costs 116,468 108,839 262,146 322,826 Net income $ 10,012 $ 8,772 $ 151,402 $ 18,893 Net income attributable to noncontrolling interests $ 4,844 $ 4,481 $ 10,316 $ 8,012
Summary of Financial Information for Unconsolidated Joint Ventures	The following represents the financial information of the Company’s unconsolidated joint ventures as presented in their unaudited financial statements (in thousands): December 31, 2018 September 30, 2019 Current assets $ 707,457 $ 778,876 Noncurrent assets 876,385 956,367 Total assets 1,583,842 1,735,243 Current liabilities 560,306 625,949 Noncurrent liabilities 813,269 895,514 Total liabilities 1,373,575 1,521,463 Total joint venture equity 210,267 213,780 Investments in and advances to unconsolidated joint ventures $ 63,560 $ 66,584 Three Months Ended Nine Months Ended September 28, 2018 September 30, 2019 September 28, 2018 September 30, 2019 Revenue $ 482,634 $ 474,600 $ 1,234,946 $ 1,225,284 Costs 462,042 452,001 1,186,184 1,166,008 Net income $ 20,592 $ 22,599 $ 48,762 $ 59,276 Equity in earnings of unconsolidated joint ventures $ 12,707 $ 7,274 $ 25,577 $ 29,305

Related Party Transactions (Tab

Related Party Transactions (Tables)	9 Months Ended
	Sep. 30, 2019
Related Party Transactions [Abstract]
Schedule of Consolidated Balance Sheet Related to Services Provided to Unconsolidated Joint Ventures	Amounts included in the consolidated balance sheets related to services the Company provided to unconsolidated joint ventures is as follows (in thousands): December 31, 2018 September 30, 2019 Accounts receivable $ 38,742 $ 44,637 Contract assets 2,648 2,734 Contract liabilities $ 10,861 $ 5,517

Fair Value of Financial Instr_2

Fair Value of Financial Instruments (Tables)	9 Months Ended
	Sep. 30, 2019
Fair Value Disclosures [Abstract]
Summary of Fair Value Assets Associated with Pension Plan	The following table sets forth assets associated with the pension plan in “Note 14 – Retirement and Other Benefit Plans” that are accounted for at fair value by Level within the fair value hierarchy. Fair value as of December 31, 2018 (in thousands): Level 1 Level 2 Level 3 Total Mutual funds $ 2,539 $ - $ - $ 2,539 Fixed income - 10,168 - 10,168 Cash and cash equivalents 361 - - 361 $ 2,900 $ 10,168 $ - $ 13,068 Fair value as of September 30, 2019 (in thousands): Level 1 Level 2 Level 3 Total Mutual funds $ 2,888 $ - $ - $ 2,888 Fixed income - 10,579 - 10,579 Cash and cash equivalents 294 - - 294 $ 3,182 $ 10,579 $ - $ 13,761
Schedule of Fair Value of Redeemable Common Stock Associated Employee Stock Ownership Plan	The following table sets forth redeemable common stock associated with the ESOP in as described in “Note 14 – Retirement and Other Benefit Plans” that is accounted for at fair value by Level within the fair value hierarchy. Fair value as of December 31, 2018 (in thousands): Level 1 Level 2 Level 3 Total Redeemable common stock $ - $ - $ 1,876,309 $ 1,876,309 Fair value as of September 30, 2019 (in thousands): Level 1 Level 2 Level 3 Total Redeemable common stock $ 2,577,011 $ - $ - $ 2,577,011
Schedule of Reconciliation Fair Value Measurements Using Significant Unobservable Inputs	The following tables present a reconciliation of the beginning and ending balances of the fair value measurements using significant unobservable inputs (Level 3) (in thousands): Balance at December 31, 2018 $ 1,876,309 Transfer to Level 1 (1,876,309 ) Balance at September 30, 2019 $ -

Earnings Per Share (Tables)

Earnings Per Share (Tables)	9 Months Ended
	Sep. 30, 2019
Earnings Per Share [Abstract]
Schedule of Weighted Average Number of Shares Used To Compute Basic and Diluted EPS	The weighted average number of shares used to compute basic and diluted EPS were: Three Months Ended Nine Months Ended September 28, 2018 September 30, 2019 September 28, 2018 September 30, 2019 Basic weighted average number of shares outstanding 79,185,527 99,434,877 80,702,032 89,977,493 Dilutive common share equivalents - - - - Diluted weighted average number of shares outstanding 79,185,527 99,434,877 80,702,032 89,977,493

Segment Information (Tables)

Segment Information (Tables)	9 Months Ended
	Sep. 30, 2019
Segment Reporting [Abstract]
Summary of Business Segment Information	The following table summarizes business segment revenue for the periods presented (in thousands): Three Months Ended Nine Months Ended September 28, 2018 September 30, 2019 September 28, 2018 September 30, 2019 Federal Solutions revenue $ 443,725 $ 486,175 $ 1,076,125 $ 1,387,484 Critical Infrastructure revenue 532,432 537,102 1,555,443 1,529,940 Total revenue $ 976,157 $ 1,023,277 $ 2,631,568 $ 2,917,424
Summary of Adjusted EBITDA Business Segment Information	The following table reconciles business segment Adjusted EBITDA attributable to Parsons Corporation to Net Income attributable to Parsons Corporation for the periods presented (in thousands): Three Months Ended Nine Months Ended Adjusted EBITDA attributable to Parsons Corporation September 28, 2018 September 30, 2019 September 28, 2018 September 30, 2019 Federal Solutions $ 45,556 $ 50,359 $ 101,052 $ 126,658 Critical Infrastructure 38,006 33,976 80,296 102,177 Adjusted EBITDA attributable to Parsons Corporation 83,562 84,335 181,348 228,835 Adjusted EBITDA attributable to noncontrolling interests 5,002 4,655 10,681 8,384 Depreciation and amortization (23,599 ) (31,027 ) (46,656 ) (92,692 ) Interest expense, net (5,589 ) (4,482 ) (12,117 ) (18,448 ) Income tax (expense) benefit (4,154 ) 15,453 (18,526 ) 67,063 Litigation-related gains(a) - - 129,674 - Amortization of deferred gain resulting from sale-leaseback transactions(b) 1,798 - 5,440 - Equity-based compensation (5,049 ) 1,657 (13,198 ) (45,504 ) Transaction-related costs(c) (2,456 ) (9,891 ) (7,511 ) (26,961 ) Restructuring(d) - (309 ) - (2,880 ) Other(e) (3,449 ) 902 (3,929 ) (2,973 ) Net income including noncontrolling interests 46,066 61,293 225,206 114,824 Net income attributable to noncontrolling interests 4,844 4,481 10,316 8,012 Net income attributable to Parsons Corporation $ 41,222 $ 56,812 $ 214,890 $ 106,812 (a) Reversal of an accrued liability, with $55.1 million recorded to revenue and $74.6 million recorded to other income (“gain associated with claim on long-term contract”) in results of operations, associated with a lawsuit against a joint venture in which the Company is the managing partner. Please see “Note 14 – Commitments and Contingencies” in the Company’s Form S-1/A filed on April 29, 2019, for a description of this matter, which was resolved in favor of the Company on June 13, 2018 (b) Reflects recognized deferred gains related to sales-leaseback transactions described in “Note 10 – Sale-Leasebacks.” ( c ) Reflects costs incurred in connection with acquisitions, the IPO, and other non-recurring transaction costs, primarily fees paid for professional services and employee retention. ( d ) Reflects costs associated with corporate restructuring initiatives. ( e ) Includes a combination of gain/loss related to sale of fixed assets, software implementation costs, and other individually insignificant items that are non-recurring in nature.
Summary of Revenues and Property and Equipment, Net by Geographic Area	The following tables presents revenues and property and equipment, net by geographic area (in thousands): Three Months Ended Nine Months Ended September 28, 2018 September 30, 2019 September 28, 2018 September 30, 2019 Revenue North America $ 805,320 $ 849,839 $ 2,131,562 $ 2,400,124 Middle East 164,677 169,028 485,377 504,604 Rest of World 6,160 4,410 14,629 12,696 Total Revenue $ 976,157 $ 1,023,277 $ 2,631,568 $ 2,917,424 The geographic location of revenue is determined by the location of the customer. The prior reporting of revenue by geographic location has been conformed to the current presentation. December 31, 2018 September 30, 2019 Property and Equipment, Net North America $ 86,847 $ 103,690 Middle East 5,002 5,548 Total Property and Equipment, Net $ 91,849 $ 109,238
Summary of Revenues by Business Lines	The following table presents revenues by business lines (in thousands): Three Months Ended Nine Months Ended September 28, 2018 September 30, 2019 September 28, 2018 September 30, 2019 Revenue Cyber & Intelligence $ 68,895 $ 90,429 $ 177,838 $ 247,710 Defense 133,259 144,160 297,318 425,603 Mission Solutions 122,780 87,936 280,902 237,914 Engineered Systems 118,791 129,989 320,067 367,542 Geospatial - 33,661 - 108,715 Federal Solutions revenues 443,725 486,175 1,076,125 1,387,484 Connected Communities 165,529 151,779 491,444 459,277 Mobility Solutions 300,523 286,199 894,796 836,779 Industrial 66,380 99,124 169,203 233,884 Critical Infrastructure revenues 532,432 537,102 1,555,443 1,529,940 Total Revenue $ 976,157 $ 1,023,277 $ 2,631,568 $ 2,917,424

Description of Operations - Add

Description of Operations - Additional Information (Details) - USD ($)	May 31, 2019	May 14, 2019	May 08, 2019	Apr. 15, 2019	Sep. 30, 2019	Sep. 28, 2018
Description Of Operations Disclosure [Line Items]
Proceeds from IPO					$ 536,879,000	$ 0
Funds to dividend through public offering		$ 52,100,000
Repayment on term loan through public offering		$ 150,000
Common stock dividend ratio				200.00%
Dividends payment, date				May 8, 2019
IPO | Common Stock
Description Of Operations Disclosure [Line Items]
Common stock shares sold			18,518,500
Common stock sold per share			$ 27
Share price		$ 25.515
Proceeds from IPO		$ 536,900,000
Underwriters | Common Stock
Description Of Operations Disclosure [Line Items]
Purchase of additional shares upon exercise of options	2,777,775
Underwriting discount per share		$ 1.485
Proceeds from IPO		$ 536,900,000

Recently Adopted Accounting P_2

Recently Adopted Accounting Pronouncements - Additional Information (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018	Dec. 30, 2017
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Retained earnings	$ (64,896)	$ 12,445
Difference between Revenue Guidance in Effect before and after Topic 606 | ASC 606
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Retained earnings			$ 4,700

Acquisitions - Additional Infor

Acquisitions - Additional Information (Details) - USD ($) $ in Thousands	Jul. 31, 2019	Jan. 07, 2019	May 31, 2018	Sep. 30, 2019	Sep. 28, 2018	Sep. 30, 2019	Sep. 30, 2018	Sep. 28, 2018	Dec. 31, 2018
Business Acquisition [Line Items]
Amortization of intangible assets				$ 22,100	$ 14,800	$ 64,500	$ 22,700
Goodwill				1,050,077		1,050,077			$ 736,938
Revenues				1,023,277	976,157	2,917,424		$ 2,631,568
Polaris Alpha
Business Acquisition [Line Items]
Percentage of ownership interest acquired			100.00%
Cash paid to acquire			$ 489,100
Borrowed under credit agreement to partially fund the acquisition			260,000
Amortization of intangible assets				13,200	13,000	41,200		17,300
Goodwill			$ 243,471	243,500		243,500
Goodwill deductible for tax purposes				50,100		50,100
Revenues				96,900	$ 94,800	293,000		$ 124,700
Polaris Alpha | Indirect, General and Administrative Expense
Business Acquisition [Line Items]
Acquisition related expenses									$ 6,200
OGSystems
Business Acquisition [Line Items]
Percentage of ownership interest acquired		100.00%
Cash paid to acquire		$ 292,400
Borrowed under credit agreement to partially fund the acquisition		110,000
Amortization of intangible assets		0		5,900		17,800
Goodwill		183,540
Goodwill deductible for tax purposes		16,000
Revenues				33,700		108,700
OGSystems | Term Loan
Business Acquisition [Line Items]
Borrowed under credit agreement to partially fund the acquisition		$ 150,000
OGSystems | Indirect, General and Administrative Expense
Business Acquisition [Line Items]
Acquisition related expenses				600		5,500
QRC Technologies
Business Acquisition [Line Items]
Percentage of ownership interest acquired	100.00%
Cash paid to acquire	$ 214,100
Amortization of intangible assets				1,900		1,900
Goodwill	128,387
Revenues				5,600		5,600
QRC Technologies | Revolving Credit Facility
Business Acquisition [Line Items]
Borrowed under credit agreement to partially fund the acquisition	$ 140,000
QRC Technologies | Indirect, General and Administrative Expense
Business Acquisition [Line Items]
Acquisition related expenses				$ 4,700		$ 4,700

Acquisitions - Summary of Estim

Acquisitions - Summary of Estimated Fair Values of Assets Acquired and Liabilities Assumed on Preliminary Purchase Price Allocation (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Jul. 31, 2019	Jan. 07, 2019	Dec. 31, 2018	May 31, 2018
Business Acquisition [Line Items]
Contract assets	$ 583,670			$ 515,319
Goodwill	1,050,077			736,938
Contract liabilities	(231,032)			$ (208,576)
Polaris Alpha
Business Acquisition [Line Items]
Cash and cash equivalents					$ 7,914
Accounts receivable					29,688
Contract assets					35,229
Prepaid expenses and other current assets					9,295
Property and equipment					9,024
Goodwill	$ 243,500				243,471
Intangible assets					199,520
Other noncurrent assets					2,203
Accounts payable					(13,942)
Accrued expenses and other current liabilities					(26,419)
Contract liabilities					(3,529)
Deferred tax liabilities					(2,231)
Other long-term liabilities					(1,146)
Net assets acquired					$ 489,077
OGSystems
Business Acquisition [Line Items]
Cash and cash equivalents			$ 5,772
Accounts receivable			9,904
Contract assets			9,747
Prepaid expenses and other current assets			4,307
Property and equipment			4,085
Right of use assets, operating leases			8,826
Goodwill			183,540
Intangible assets			92,300
Other noncurrent assets			10
Accounts payable			(5,450)
Accrued expenses and other current liabilities			(7,147)
Contract liabilities			(1,300)
Short-term lease liabilities, operating leases			(805)
Income tax payable			(1,469)
Deferred tax liabilities			(904)
Long-term lease liabilities, operating leases			(8,021)
Other long-term liabilities			(1,015)
Net assets acquired			$ 292,380
QRC Technologies
Business Acquisition [Line Items]
Cash and cash equivalents		$ 5,925
Accounts receivable		5,587
Prepaid expenses and other current assets		5,467
Property and equipment		1,205
Right of use assets, operating leases		5,228
Goodwill		128,387
Intangible assets		72,900
Accounts payable		(1,567)
Accrued expenses and other current liabilities		(3,771)
Short-term lease liabilities, operating leases		(545)
Long-term lease liabilities, operating leases		(4,683)
Net assets acquired		$ 214,133

Acquisitions - Schedule of Inta

Acquisitions - Schedule of Intangible Assets Value on Purchase Price (Details) - USD ($) $ in Thousands	Jul. 31, 2019	Jan. 07, 2019	May 31, 2018	Sep. 30, 2019
Developed Technology
Acquired Finite Lived Intangible Assets [Line Items]
Amortization Period (in years)				4 years
Developed Technology | Polaris Alpha
Acquired Finite Lived Intangible Assets [Line Items]
Gross Carrying Amount			$ 84,900
Amortization Period (in years)			4 years
Developed Technology | OGSystems
Acquired Finite Lived Intangible Assets [Line Items]
Gross Carrying Amount		$ 1,300
Amortization Period (in years)		3 years
Developed Technology | QRC Technologies
Acquired Finite Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 22,600
Developed Technology | QRC Technologies | Minimum
Acquired Finite Lived Intangible Assets [Line Items]
Amortization Period (in years)	3 years
Developed Technology | QRC Technologies | Maximum
Acquired Finite Lived Intangible Assets [Line Items]
Amortization Period (in years)	5 years
Customer Relationships
Acquired Finite Lived Intangible Assets [Line Items]
Amortization Period (in years)				7 years
Customer Relationships | Polaris Alpha
Acquired Finite Lived Intangible Assets [Line Items]
Gross Carrying Amount			$ 76,000
Amortization Period (in years)			8 years
Customer Relationships | OGSystems
Acquired Finite Lived Intangible Assets [Line Items]
Gross Carrying Amount		$ 57,100
Amortization Period (in years)		5 years
Customer Relationships | QRC Technologies
Acquired Finite Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 47,600
Amortization Period (in years)	12 years
Backlog
Acquired Finite Lived Intangible Assets [Line Items]
Amortization Period (in years)				3 years
Backlog | Polaris Alpha
Acquired Finite Lived Intangible Assets [Line Items]
Gross Carrying Amount			$ 34,900
Amortization Period (in years)			2 years
Backlog | OGSystems
Acquired Finite Lived Intangible Assets [Line Items]
Gross Carrying Amount		$ 27,700
Amortization Period (in years)		3 years
Backlog | QRC Technologies
Acquired Finite Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 700
Amortization Period (in years)	1 year
Trade Name
Acquired Finite Lived Intangible Assets [Line Items]
Amortization Period (in years)				1 year
Trade Name | Polaris Alpha
Acquired Finite Lived Intangible Assets [Line Items]
Gross Carrying Amount			$ 3,600
Amortization Period (in years)			1 year
Trade Name | OGSystems
Acquired Finite Lived Intangible Assets [Line Items]
Gross Carrying Amount		$ 3,800
Amortization Period (in years)		2 years
Trade Name | QRC Technologies
Acquired Finite Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 800
Amortization Period (in years)	2 years
Leases
Acquired Finite Lived Intangible Assets [Line Items]
Amortization Period (in years)				5 years
Leases | Polaris Alpha
Acquired Finite Lived Intangible Assets [Line Items]
Gross Carrying Amount			$ 120
Amortization Period (in years)			6 years
Non compete Agreements
Acquired Finite Lived Intangible Assets [Line Items]
Amortization Period (in years)				3 years
Non compete Agreements | OGSystems
Acquired Finite Lived Intangible Assets [Line Items]
Gross Carrying Amount		$ 2,400
Amortization Period (in years)		3 years
Non compete Agreements | QRC Technologies
Acquired Finite Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 1,200
Amortization Period (in years)	4 years

Acquisitions - Schedule of Supp

Acquisitions - Schedule of Supplemental Pro Forma Information (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 28, 2018	Sep. 30, 2019	Sep. 28, 2018
Polaris Alpha
Business Acquisition [Line Items]
Pro forma revenue		$ 976,157		$ 2,784,864
Pro forma net income including noncontrolling interests		46,848		179,071
OGSystems
Business Acquisition [Line Items]
Pro forma revenue	$ 1,023,277	1,007,793	$ 2,919,379	2,715,572
Pro forma net income including noncontrolling interests	61,293	39,224	118,896	196,905
QRC Technologies
Business Acquisition [Line Items]
Pro forma revenue	1,026,831	987,343	2,938,973	2,657,105
Pro forma net income including noncontrolling interests	$ 65,782	$ 44,944	$ 117,399	$ 212,728

Contracts with Customers - Summ

Contracts with Customers - Summary of Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 28, 2018	Sep. 30, 2019	Sep. 28, 2018
Disaggregation Of Revenue [Line Items]
Revenues	$ 1,023,277	$ 976,157	$ 2,917,424	$ 2,631,568
Fixed-Price
Disaggregation Of Revenue [Line Items]
Revenues	288,316	300,225	850,658	833,224
Time-and-Materials
Disaggregation Of Revenue [Line Items]
Revenues	285,586	254,435	810,656	732,555
Cost-Plus
Disaggregation Of Revenue [Line Items]
Revenues	$ 449,375	$ 421,497	$ 1,256,110	$ 1,065,789

Contracts with Customers - Su_2

Contracts with Customers - Summary of Contract Assets and Contract Liabilities (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2019	Dec. 31, 2018
Revenue From Contract With Customer [Abstract]
Contract assets	$ 583,670	$ 515,319
Contract liabilities	231,032	208,576
Net contract assets (liabilities)	352,638	$ 306,743
Change in contract assets	68,351
Change in contract liabilities	22,456
Change in contract assets and liabilities	$ 45,895
Percentage change in contract assets	13.30%
Percentage change in contract liabilities	10.80%
Percentage change in contract assets and liabilities	15.00%

Contracts with Customers - Su_3

Contracts with Customers - Summary of Contract Assets and Contract Liabilities (Parenthetical) (Details) - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018
Revenue From Contract With Customer [Abstract]
Contract retentions	$ 87.1	$ 89.6
Contract retentions, not expected to be paid in next 12 months	39.7
Contract assets, unapproved change orders, claims, and requests	$ 58.9	$ 47.1

Contracts with Customers - Addi

Contracts with Customers - Additional Information (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 28, 2018	Sep. 30, 2019	Sep. 28, 2018
Revenue From Contract With Customer [Abstract]
Revenue recognized included contract liability	$ 2,100,000	$ 800,000	$ 115,100,000	$ 100,400,000
Impairment of contract assets	0	0	0	0
Impact of changes in estimated claims or incentives on revenue	5,000,000	0	5,000,000	0
Increase in revenue due to Impact of changes in estimated claims or incentives	9,100,000	$ 0	9,100,000	$ 0
Remaining unsatisfied performance obligations	$ 5,100,000,000		$ 5,100,000,000

Contracts with Customers - Su_4

Contracts with Customers - Summary of Changes in Contract Assets and Contract Liabilities (Details) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2019	Dec. 31, 2018
Revenue From Contract With Customer [Abstract]
Acquired contract assets	$ 9,747	$ 35,229
Acquired contract liabilities	1,300	3,529
Change in the estimate of variable consideration	14,506	0
Reversal of provision for contract losses	$ 0	$ 133,180

Contracts with Customers - Su_5

Contracts with Customers - Summary of Changes in Contract Assets and Contract Liabilities (Parenthetical) (Details) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2019	Dec. 31, 2018
Revenue From Contract With Customer [Abstract]
Reversal for provision for contract losses	$ 0	$ 133,180
Increase in revenue recorded in other income		$ 55,100

Contracts with Customers - Su_6

Contracts with Customers - Summary of Accounts Receivable, Net (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Revenue From Contract With Customer [Abstract]
Billed	$ 516,099	$ 538,808
Unbilled	200,477	135,180
Total accounts receivable, gross	716,576	673,988
Allowance for doubtful accounts	(42,902)	(50,702)
Total accounts receivable, net	$ 673,674	$ 623,286

Contracts with Customers - Su_7

Contracts with Customers - Summary of Remaining Unsatisfied Performance Obligations Expect to Satisfy (Details) $ in Thousands	Sep. 30, 2019USD ($)
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Remaining unsatisfied performance obligations	$ 5,100,000
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2019-10-01
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Remaining unsatisfied performance obligations	$ 2,835,159
Revenue, remaining performance obligation, expected timing of satisfaction, period	3 months
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2020-01-01
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Remaining unsatisfied performance obligations	$ 1,397,089
Revenue, remaining performance obligation, expected timing of satisfaction, period	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2021-01-01
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Remaining unsatisfied performance obligations	$ 851,904
Revenue, remaining performance obligation, expected timing of satisfaction, period
Federal Solution Segment | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2019-10-01
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Remaining unsatisfied performance obligations	$ 1,198,634
Revenue, remaining performance obligation, expected timing of satisfaction, period	3 months
Federal Solution Segment | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2020-01-01
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Remaining unsatisfied performance obligations	$ 436,620
Revenue, remaining performance obligation, expected timing of satisfaction, period	1 year
Federal Solution Segment | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2021-01-01
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Remaining unsatisfied performance obligations	$ 208,734
Revenue, remaining performance obligation, expected timing of satisfaction, period
Critical Infrastructure | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2019-10-01
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Remaining unsatisfied performance obligations	$ 1,636,525
Revenue, remaining performance obligation, expected timing of satisfaction, period	3 months
Critical Infrastructure | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2020-01-01
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Remaining unsatisfied performance obligations	$ 960,469
Revenue, remaining performance obligation, expected timing of satisfaction, period	1 year
Critical Infrastructure | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2021-01-01
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Remaining unsatisfied performance obligations	$ 643,170
Revenue, remaining performance obligation, expected timing of satisfaction, period

Leases - Additional Information

Leases - Additional Information (Details) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended	9 Months Ended
	Jan. 31, 2019	Sep. 28, 2018	Sep. 30, 2019	Sep. 28, 2018	Dec. 31, 2018
Lessee Lease Description [Line Items]
Lease option to extend			five years
Lease existence of option to extend			true
Lease option to terminate			seventh year
Lease existence of option to terminate			true
Finance lease right-of-use asset			$ 1,800
Finance lease right of use assets accumulated depreciation			500
Operating lease not yet commenced expense			$ 37,000
Minimum rental commitments on operating leases, current					$ 276,700
Minimum rental commitments on operating leases, 2019					67,900
Minimum rental commitments on operating leases, 2020					51,000
Minimum rental commitments on operating leases, 2021					42,500
Minimum rental commitments on operating leases, 2022					35,900
Minimum rental commitments on operating leases, 2023					29,400
Minimum rental commitments on operating leases, thereafter					$ 50,000
Rent expense		$ 21,700		$ 59,700
Minimum [Member]
Lessee Lease Description [Line Items]
Lease term of contract			1 year
Operating lease not yet commenced term of contract			2 years
Maximum [Member]
Lessee Lease Description [Line Items]
Lease term of contract			10 years
Operating lease not yet commenced term of contract			11 years
Accounting Standards Update 2016-02
Lessee Lease Description [Line Items]
Cumulative effect adjustment to retained earnings			$ 52,608
Accounting Standards Update 2016-02 | Net Deferred Tax Asset
Lessee Lease Description [Line Items]
Cumulative effect adjustment to retained earnings			52,600
Accounting Standards Update 2016-02 | Deferred Tax Asset
Lessee Lease Description [Line Items]
Cumulative effect adjustment to retained earnings	$ 700		$ 700

Leases - Summary of Lease Costs

Leases - Summary of Lease Costs (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2019
Leases [Abstract]
Operating lease cost	$ 17,969	$ 53,835
Short-term lease cost	5,429	10,925
Amortization of right-of-use assets	120	455
Interest on lease liabilities	15	46
Sublease income	(712)	(2,727)
Total lease cost	$ 22,821	$ 62,534

Leases - Schedule of Supplement

Leases - Schedule of Supplemental Cash Flow Information Related to Leases (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2019USD ($)
Leases [Abstract]
Operating cash flows for operating leases	$ 52,056
Operating cash flows for financing activities	570
Right-of-use assets obtained in exchange for new operating lease liabilities	274,212
Right-of-use assets obtained in exchange for new finance lease liabilities	$ 1,818

Leases - Schedule of Suppleme_2

Leases - Schedule of Supplemental Balance Sheet and Other Information Related to Leases (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Operating Leases:
Right of use assets, operating leases	$ 219,207	$ 0
Lease liabilities:
Short-term lease liabilities, operating leases	49,074	0
Long-term lease liabilities, operating leases	188,571	$ 0
Total operating lease liabilities	237,645
Finance Leases:
Other noncurrent assets	1,362
Lease liabilities:
Accrued expenses and other current liabilities	$ 558
Finance Lease, Liability, Current, Statement of Financial Position [Extensible List]	psn:AccruedExpensesAndOtherCurrentLiabilities
Other long-term liabilities	$ 736
Finance Lease, Liability, Noncurrent, Statement of Financial Position [Extensible List]	us-gaap:OtherLiabilitiesNoncurrent
Total finance lease liabilities	$ 1,294
Weighted Average Remaining Lease Term:
Operating leases	6 years
Finance leases	3 years
Weighted Average Discount Rate:
Operating leases	4.30%
Finance leases	4.40%

Leases - Schedule of Maturity A

Leases - Schedule of Maturity Analysis of Future Undiscounted Cash Flows (Details) $ in Thousands	Sep. 30, 2019USD ($)
Operating Leases
2019	$ 15,409
2020	54,561
2021	50,333
2022	44,160
2023	36,996
Thereafter	64,423
Total lease payments	265,882
Less: imputed interest	(28,237)
Total present value of lease liabilities	237,645
Finance Leases
2019	160
2020	574
2021	421
2022	187
2023	25
Thereafter	0
Total lease payments	1,367
Less: imputed interest	(73)
Total present value of lease liabilities	$ 1,294

Goodwill - Summary of Changes i

Goodwill - Summary of Changes in Carrying Value of Goodwill by Reporting Segment (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2019USD ($)
Goodwill [Line Items]
Beginning Balance	$ 736,938
Acquisitions	311,860
Foreign Exchange	1,279
Ending Balance	1,050,077
Federal Solutions
Goodwill [Line Items]
Beginning Balance	666,841
Acquisitions	311,860
Foreign Exchange	0
Ending Balance	978,701
Critical Infrastructure
Goodwill [Line Items]
Beginning Balance	70,097
Acquisitions	0
Foreign Exchange	1,279
Ending Balance	$ 71,376

Intangible Assets - Schedule of

Intangible Assets - Schedule of Gross Amount and Accumulated Amortization of Intangible Assets (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2019	Dec. 31, 2018
Acquired Finite Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 460,769	$ 294,767
Accumulated Amortization	(179,612)	(115,249)
Net Carrying Amount	281,157	179,518
Backlog
Acquired Finite Lived Intangible Assets [Line Items]
Gross Carrying Amount	109,155	80,754
Accumulated Amortization	(80,321)	(58,295)
Net Carrying Amount	$ 28,834	22,459
Amortization Period (in years)	3 years
Customer Relationships
Acquired Finite Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 226,329	121,629
Accumulated Amortization	(60,266)	(38,974)
Net Carrying Amount	$ 166,063	82,655
Amortization Period (in years)	7 years
Leases
Acquired Finite Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 670	670
Accumulated Amortization	(576)	(561)
Net Carrying Amount	$ 94	109
Amortization Period (in years)	5 years
Developed Technology
Acquired Finite Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 111,739	87,839
Accumulated Amortization	(32,545)	(15,174)
Net Carrying Amount	$ 79,194	72,665
Amortization Period (in years)	4 years
Trade Name
Acquired Finite Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 8,200	3,600
Accumulated Amortization	(5,092)	(2,100)
Net Carrying Amount	$ 3,108	1,500
Amortization Period (in years)	1 year
Non compete Agreements
Acquired Finite Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 3,600	0
Accumulated Amortization	(650)	0
Net Carrying Amount	$ 2,950	0
Amortization Period (in years)	3 years
Other Intangibles
Acquired Finite Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 1,076	275
Accumulated Amortization	(162)	(145)
Net Carrying Amount	$ 914	$ 130
Amortization Period (in years)	10 years

Intangible Assets - Additional

Intangible Assets - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 28, 2018	Sep. 30, 2019	Sep. 30, 2018
Goodwill And Intangible Assets Disclosure [Abstract]
Amortization expense of intangible assets	$ 22.1	$ 14.8	$ 64.5	$ 22.7

Intangible Assets - Schedule _2

Intangible Assets - Schedule of Estimated Amortization Expense (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Goodwill And Intangible Assets Disclosure [Abstract]
2019 (remaining)	$ 23,049
2020	83,511
2021	78,778
2022	34,517
2023	22,599
Thereafter	38,703
Net Carrying Amount	$ 281,157	$ 179,518

Property and Equipment, Net (De

Property and Equipment, Net (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2019	Dec. 31, 2018
Property Plant And Equipment [Line Items]
Accumulated depreciation	$ (227,776)	$ (204,533)
Property and equipment, net	109,238	91,849
Buildings and Leasehold Improvements
Property Plant And Equipment [Line Items]
Property and equipment, gross	$ 71,698	54,348
Buildings and Leasehold Improvements | Minimum [Member]
Property Plant And Equipment [Line Items]
Useful lives (years)	1 year
Buildings and Leasehold Improvements | Maximum [Member]
Property Plant And Equipment [Line Items]
Useful lives (years)	15 years
Furniture and Equipment
Property Plant And Equipment [Line Items]
Property and equipment, gross	$ 85,322	81,705
Furniture and Equipment | Minimum [Member]
Property Plant And Equipment [Line Items]
Useful lives (years)	3 years
Furniture and Equipment | Maximum [Member]
Property Plant And Equipment [Line Items]
Useful lives (years)	10 years
Computer Systems and Equipment
Property Plant And Equipment [Line Items]
Property and equipment, gross	$ 168,241	148,255
Computer Systems and Equipment | Minimum [Member]
Property Plant And Equipment [Line Items]
Useful lives (years)	3 years
Computer Systems and Equipment | Maximum [Member]
Property Plant And Equipment [Line Items]
Useful lives (years)	10 years
Construction Equipment
Property Plant And Equipment [Line Items]
Property and equipment, gross	$ 11,753	$ 12,074
Construction Equipment | Minimum [Member]
Property Plant And Equipment [Line Items]
Useful lives (years)	5 years
Construction Equipment | Maximum [Member]
Property Plant And Equipment [Line Items]
Useful lives (years)	7 years

Property and Equipment, Net - A

Property and Equipment, Net - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 28, 2018	Sep. 30, 2019	Sep. 28, 2018
Property Plant And Equipment [Abstract]
Depreciation expense	$ 8.9	$ 8.8	$ 28.2	$ 24

Sale-Leasebacks - Additional In

Sale-Leasebacks - Additional Information (Detail) $ in Thousands	1 Months Ended	3 Months Ended		9 Months Ended		12 Months Ended
	Jan. 31, 2019USD ($)	Sep. 30, 2019USD ($)	Sep. 28, 2018USD ($)	Sep. 30, 2019USD ($)	Sep. 28, 2018USD ($)	Dec. 31, 2011USD ($)building	Dec. 31, 2018USD ($)
Sale Leaseback Transaction [Line Items]
Sale leaseback transaction, description				During fiscal 2011, the Company consummated two sale-leaseback transactions associated with the sale of two office buildings
Number of sale leaseback transaction associated with sale | building						2
Gain recognized to the sale leaseback transaction						$ 106,700
Deferred gain resulting from sale-leaseback transactions		$ 0		$ 0		$ 107,800	$ 46,004
Amortization of deferred gain		$ 0	$ 1,798	0	$ 5,440
Accounting Standards Update 2016-02
Sale Leaseback Transaction [Line Items]
Deferred gain balance recognized							$ 53,300
Cumulative effect adjustment to retained earnings				52,608
Accounting Standards Update 2016-02 | Deferred Tax Asset
Sale Leaseback Transaction [Line Items]
Cumulative effect adjustment to retained earnings	$ 700			$ 700

Debt and Credit Facilities - Sc

Debt and Credit Facilities - Schedule of Long Term Debt (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Debt Instrument [Line Items]
Long-Term Debt issuance costs	$ (694)	$ (836)
Total long-term	249,306	429,164
Revolving Credit Facility
Debt Instrument [Line Items]
Long-term debt	0	180,000
Senior Notes
Debt Instrument [Line Items]
Long-term debt	$ 250,000	$ 250,000

Debt and Credit Facilities - Ad

Debt and Credit Facilities - Additional Information (Details) - USD ($)	May 10, 2019	Jul. 01, 2014	Sep. 30, 2019	Sep. 28, 2018	Sep. 30, 2019	Sep. 28, 2018	Jan. 31, 2019	Dec. 31, 2018
Debt Instrument [Line Items]
Debt issuance costs incurred			$ 500,000		$ 500,000
Letters of credit outstanding amount			220,600,000		220,600,000			$ 223,000,000
Amortization of debt issue costs			200,000	$ 200,000	802,000	$ 548,000
Term Loan
Debt Instrument [Line Items]
Interest expense			0		2,300,000
Repayment of outstanding balance	$ 150,000,000
Debt Amount							$ 150,000,000
Accrued Expenses and Other Current Liabilities
Debt Instrument [Line Items]
Interest payable			2,600,000		2,600,000			5,700,000
Senior Notes
Debt Instrument [Line Items]
Interest expense			9,300,000	3,100,000	9,300,000	3,100,000
Interest payments			12,400,000	6,200,000	12,400,000	6,200,000
Senior Notes | Level 2
Debt Instrument [Line Items]
Estimated fair value			269,300,000		269,300,000
Private Placement
Debt Instrument [Line Items]
Debt issuance costs incurred			1,100,000		$ 1,100,000
Repayment of outstanding balance		$ 250,000,000
Credit Agreement
Debt Instrument [Line Items]
Amended and restated credit agreement date					Nov. 30, 2017
Debt issuance costs incurred			2,000,000		$ 2,000,000
Revolving credit facility			500,000,000		500,000,000
Increase in revolving credit facility			550,000,000		$ 550,000,000
Credit agreement extended date					Nov. 30, 2022
Letters of credit outstanding amount			45,200,000		$ 45,200,000			$ 49,800,000
Interest expense			$ 1,100,000	$ 2,500,000	$ 6,400,000	$ 3,500,000
Credit Agreement | Minimum
Debt Instrument [Line Items]
Interest rate								4.253%
Credit Agreement | Maximum
Debt Instrument [Line Items]
Interest rate			3.35%		3.35%
Credit Agreement | Base Rate | Minimum
Debt Instrument [Line Items]
Margin interest rate					0.125%
Credit Agreement | Base Rate | Maximum
Debt Instrument [Line Items]
Margin interest rate					1.00%
Credit Agreement | LIBOR | Minimum
Debt Instrument [Line Items]
Margin interest rate					1.125%
Credit Agreement | LIBOR | Maximum
Debt Instrument [Line Items]
Margin interest rate					2.00%

Debt and Credit Facilities - _2

Debt and Credit Facilities - Schedule of Aggregate Amount Debt Repayable (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2019USD ($)
Senior Note, Series A
Debt Instrument [Line Items]
Debt Amount	$ 50,000
Maturity Date	Jul. 15, 2021
Interest Rates	4.44%
Senior Note, Series B
Debt Instrument [Line Items]
Debt Amount	$ 100,000
Maturity Date	Jul. 15, 2024
Interest Rates	4.98%
Senior Note, Series C
Debt Instrument [Line Items]
Debt Amount	$ 60,000
Maturity Date	Jul. 15, 2026
Interest Rates	5.13%
Senior Note, Series D
Debt Instrument [Line Items]
Debt Amount	$ 40,000
Maturity Date	Jul. 15, 2029
Interest Rates	5.38%

Income Taxes - Additional Infor

Income Taxes - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2019	Jun. 30, 2019	Sep. 30, 2019	Sep. 28, 2018	Dec. 29, 2017	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Effective Corporation tax benefit rate percentage			69.69%
U.S. corporate tax rate	21.00%		21.00%		35.00%
Deferred tax benefit		$ 56,000	$ 105,161	$ (1,281)
Revised estimated effects of change in tax status based upon forecasted temporary differences	$ 85,000
Expected Income tax benefit	29,000
Discrete tax benefit	29,000
Deferred tax assets valuation allowance	18,100		18,100
Liability for income taxes associated with uncertain tax positions	$ 14,600		$ 14,600			$ 9,900

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Details)	Mar. 01, 2017USD ($)	Sep. 30, 2019Claim
Legal Proceedings [Line Items]
Number of claims outstanding | Claim		0
Minimum
Legal Proceedings [Line Items]
Loss contingency damages value | $	$ 100,000,000

Retirement and Other Benefit _2

Retirement and Other Benefit Plans - Additional Information (Details) - USD ($)	Apr. 15, 2019	Apr. 03, 2019	Sep. 30, 2019	Sep. 28, 2018	Sep. 30, 2019	Sep. 28, 2018	Dec. 31, 2018
Employee Stock Ownership Plan (ESOP) Disclosures [Line Items]
Shares fully vested, Description					Shares allocated to a participant’s account are fully vested after six years of credited service, or in the event(s) of reaching age 65, death or disability while an active employee of the Company.
Shares fully vested after credited service					6 years
Company's stock held by ESOP			78,138,602		78,138,602		78,172,809
ESOP shares aggregate redemption, value			$ 2,600,000,000		$ 2,600,000,000		$ 1,900,000,000
Dividends payment, date	May 8, 2019
Dividends declared amount							0
Other Noncurrent Assets
Employee Stock Ownership Plan (ESOP) Disclosures [Line Items]
Defined benefit pension plan, net assets position			1,700,000		1,700,000		$ 1,700,000
Board of Directors
Employee Stock Ownership Plan (ESOP) Disclosures [Line Items]
Common stock dividend ratio	2
Common stock dividend date	May 7, 2019
Initial public offering date	May 8, 2019
Common stock dividend payment date	May 8, 2019
IPO | Board of Directors
Employee Stock Ownership Plan (ESOP) Disclosures [Line Items]
Dividends payable, amount per share		$ 2
Dividends payable		$ 52,100,000
Dividends payment, date		May 10, 2019
Direct Costs of Contracts and Indirect, General and Administrative Expense
Employee Stock Ownership Plan (ESOP) Disclosures [Line Items]
ESOP contribution expense			$ 12,300,000	$ 11,400,000	$ 36,800,000	$ 34,100,000

Investments in and Advances t_3

Investments in and Advances to Joint Ventures - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 28, 2018	Sep. 30, 2019	Sep. 28, 2018	Dec. 31, 2018
Schedule Of Equity Method Investments [Line Items]
Letters of credit outstanding amount	$ 220.6		$ 220.6		$ 223
Unconsolidated Joint Ventures
Schedule Of Equity Method Investments [Line Items]
Net distributions from (contributions to) unconsolidated joint ventures	13.7	$ 20.1	28	$ 28.6
Consolidated Joint Ventures
Schedule Of Equity Method Investments [Line Items]
Letters of credit outstanding amount	$ 72.4		$ 72.4		$ 76.8

Investments in and Advances t_4

Investments in and Advances to Joint Ventures - Summary of Financial Information for Consolidated Joint Ventures (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 28, 2018	Sep. 30, 2019	Sep. 28, 2018	Dec. 31, 2018
Schedule Of Equity Method Investments [Line Items]
Current assets	$ 1,474,261		$ 1,474,261		$ 1,488,807
Total assets	3,362,644		3,362,644		2,612,578
Current liabilities	1,156,259		1,156,259		1,006,161
Total liabilities	1,768,193		1,768,193		1,657,345
Total joint venture equity	(1,010,654)		(1,010,654)		(967,537)
Revenues	1,023,277	$ 976,157	2,917,424	$ 2,631,568
Costs	798,552	783,018	2,297,512	2,054,201
Net income attributable to Parsons Corporation	56,812	41,222	106,812	214,890
Net income attributable to noncontrolling interests	4,481	4,844	8,012	10,316
Consolidated Joint Ventures
Schedule Of Equity Method Investments [Line Items]
Current assets	254,204		254,204		287,227
Noncurrent assets	2,836		2,836		2,689
Total assets	257,040		257,040		289,916
Current liabilities	198,079		198,079		199,833
Total liabilities	198,079		198,079		199,833
Total joint venture equity	58,961		58,961		$ 90,083
Revenues	117,611	126,480	341,719	413,548
Costs	108,839	116,468	322,826	262,146
Net income attributable to Parsons Corporation	8,772	10,012	18,893	151,402
Net income attributable to noncontrolling interests	$ 4,481	$ 4,844	$ 8,012	$ 10,316

Investments in and Advances t_5

Investments in and Advances to Joint Ventures - Summary of Financial Information for Unconsolidated Joint Ventures (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 28, 2018	Sep. 30, 2019	Sep. 28, 2018	Dec. 31, 2018
Schedule Of Equity Method Investments [Line Items]
Current assets	$ 1,474,261		$ 1,474,261		$ 1,488,807
Total assets	3,362,644		3,362,644		2,612,578
Current liabilities	1,156,259		1,156,259		1,006,161
Total liabilities	1,768,193		1,768,193		1,657,345
Total joint venture equity	(1,010,654)		(1,010,654)		(967,537)
Investments in and advances to unconsolidated joint ventures	66,584		66,584		63,560
Revenues	1,023,277	$ 976,157	2,917,424	$ 2,631,568
Costs	798,552	783,018	2,297,512	2,054,201
Net income attributable to Parsons Corporation	56,812	41,222	106,812	214,890
Equity in earnings of unconsolidated joint ventures	7,274	12,707	29,305	25,577
Unconsolidated Joint Ventures
Schedule Of Equity Method Investments [Line Items]
Current assets	778,876		778,876		707,457
Noncurrent assets	956,367		956,367		876,385
Total assets	1,735,243		1,735,243		1,583,842
Current liabilities	625,949		625,949		560,306
Noncurrent liabilities	895,514		895,514		813,269
Total liabilities	1,521,463		1,521,463		1,373,575
Total joint venture equity	213,780		213,780		210,267
Investments in and advances to unconsolidated joint ventures	66,584		66,584		$ 63,560
Revenues	474,600	482,634	1,225,284	1,234,946
Costs	452,001	462,042	1,166,008	1,186,184
Net income attributable to Parsons Corporation	22,599	20,592	59,276	48,762
Equity in earnings of unconsolidated joint ventures	$ 7,274	$ 12,707	$ 29,305	$ 25,577

Related Party Transactions - Ad

Related Party Transactions - Additional Information (Details) - Unconsolidated joint ventures - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 28, 2018	Sep. 30, 2019	Sep. 28, 2018
Related Party Transaction [Line Items]
Revenues	$ 28,800	$ 36,600	$ 113,100	$ 112,200
Reimbursable cost incurred	$ 20,500	$ 28,200	$ 86,300	$ 85,200

Related Party Transactions - Sc

Related Party Transactions - Schedule of Consolidated Balance Sheet Related to Services Provided to Unconsolidated Joint Ventures (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Related Party Transaction [Line Items]
Contract assets	$ 583,670	$ 515,319
Contract liabilities	231,032	208,576
Unconsolidated Joint Ventures
Related Party Transaction [Line Items]
Accounts receivable	44,637	38,742
Contract assets	2,734	2,648
Contract liabilities	$ 5,517	$ 10,861

Fair Value of Financial Instr_3

Fair Value of Financial Instruments - Summary of Assets Associated with Pension Plan (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Assets, fair value disclosure	$ 13,761	$ 13,068
Level 1
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Assets, fair value disclosure	3,182	2,900
Level 2
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Assets, fair value disclosure	10,579	10,168
Level 3
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Assets, fair value disclosure	0	0
Mutual Funds
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Assets, fair value disclosure	2,888	2,539
Mutual Funds | Level 1
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Assets, fair value disclosure	2,888	2,539
Mutual Funds | Level 2
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Assets, fair value disclosure	0	0
Mutual Funds | Level 3
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Assets, fair value disclosure	0	0
Fixed Income
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Assets, fair value disclosure	10,579	10,168
Fixed Income | Level 1
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Assets, fair value disclosure	0	0
Fixed Income | Level 2
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Assets, fair value disclosure	10,579	10,168
Fixed Income | Level 3
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Assets, fair value disclosure	0	0
Cash and Cash Equivalents
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Assets, fair value disclosure	294	361
Cash and Cash Equivalents | Level 1
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Assets, fair value disclosure	294	361
Cash and Cash Equivalents | Level 2
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Assets, fair value disclosure	0	0
Cash and Cash Equivalents | Level 3
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Assets, fair value disclosure	$ 0	$ 0

Fair Value of Financial Instr_4

Fair Value of Financial Instruments - Summary of Redeemable Common Stock Associated with ESOP (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Redeemable common stock	$ 2,577,011	$ 1,876,309
Level 1
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Redeemable common stock	2,577,011	0
Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Redeemable common stock	0	0
Level 3
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Redeemable common stock	$ 0	$ 1,876,309

Fair Value of Financial Instr_5

Fair Value of Financial Instruments - Additional Information (Details) - USD ($) $ in Billions	Sep. 30, 2019	Dec. 31, 2018
Fair Value Disclosures [Abstract]
Shares held by ESOP	78,138,602	78,172,809
Shares held by ESOP, redemption values	$ 2.6	$ 1.9

Fair Value of Financial Instr_6

Fair Value of Financial Instruments - Schedule of Reconciliation Fair Value Measurements Using Significant Unobservable Inputs (Details) - Level 3 $ in Thousands	9 Months Ended
	Sep. 30, 2019USD ($)
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Balance at December 31, 2018	$ 1,876,309
Transfer to Level 1	(1,876,309)
Balance at September 30, 2019	$ 0

Earnings Per Share - Additional

Earnings Per Share - Additional Information (Details) - shares	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 28, 2018	Sep. 30, 2019	Sep. 28, 2018
Earnings Per Share [Abstract]
Dilutive securities outstanding	0	0	0	0

Earnings Per Share - Schedule o

Earnings Per Share - Schedule of Weighted Average Number of Shares Used To Compute Basic and Diluted EPS (Details) - shares	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 28, 2018	Sep. 30, 2019	Sep. 28, 2018
Earnings Per Share [Abstract]
Basic weighted average number of shares outstanding	99,434,877	79,185,527	89,977,493	80,702,032
Dilutive common share equivalents	0	0	0	0
Diluted weighted average number of shares outstanding	99,434,877	79,185,527	89,977,493	80,702,032

Segment Information - Additiona

Segment Information - Additional Information (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019USD ($)	Sep. 28, 2018USD ($)	Sep. 30, 2019USD ($)segment	Sep. 28, 2018USD ($)	Dec. 31, 2018USD ($)
Segment Reporting Information [Line Items]
Number of reportable segments | segment			2
Revenues	$ 1,023,277	$ 976,157	$ 2,917,424	$ 2,631,568
Property and equipment, net	109,238		109,238		$ 91,849
Reversal of accrued liability	0		0	129,674
Critical Infrastructure
Segment Reporting Information [Line Items]
Revenues	537,102	532,432	1,529,940	1,555,443
Revenue Excluding Claim Settlement				1,500,000
Critical Infrastructure | Mobility Solutions
Segment Reporting Information [Line Items]
Revenues	286,199	300,523	836,779	894,796
Revenue Excluding Claim Settlement				839,700
Revenue
Segment Reporting Information [Line Items]
Reversal of accrued liability				55,100
Revenue | Critical Infrastructure | Mobility Solutions
Segment Reporting Information [Line Items]
Reversal of accrued liability		55,100		55,100
United States
Segment Reporting Information [Line Items]
Revenues	774,200	$ 747,700	2,200	$ 2,000
Property and equipment, net	$ 97,300		$ 97,300		$ 79,900

Segment Information - Summary o

Segment Information - Summary of Business Segment Information (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 28, 2018	Sep. 30, 2019	Sep. 28, 2018
Segment Reporting Information [Line Items]
Total revenue	$ 1,023,277	$ 976,157	$ 2,917,424	$ 2,631,568
Federal Solution Segment
Segment Reporting Information [Line Items]
Total revenue	486,175	443,725	1,387,484	1,076,125
Critical Infrastructure
Segment Reporting Information [Line Items]
Total revenue	$ 537,102	$ 532,432	$ 1,529,940	$ 1,555,443

Segment Information - Summary_2

Segment Information - Summary of Adjusted EBITDA Business Segment Information (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 28, 2018	Sep. 30, 2019	Sep. 28, 2018
Adjusted EBITDA attributable to Parsons Corporation
Adjusted EBITDA attributable to Parsons Corporation	$ 84,335	$ 83,562	$ 228,835	$ 181,348
Adjusted EBITDA attributable to noncontrolling interests	4,655	5,002	8,384	10,681
Depreciation and amortization	(31,027)	(23,599)	(92,692)	(46,656)
Interest expense, net	(4,482)	(5,589)	(18,448)	(12,117)
Income tax (expense) benefit	15,453	(4,154)	67,063	(18,526)
Litigation-related gains	0		0	129,674
Amortization of deferred gain resulting from sale-leaseback transactions	0	1,798	0	5,440
Equity-based compensation	1,657	(5,049)	(45,504)	(13,198)
Transaction-related costs	(9,891)	(2,456)	(26,961)	(7,511)
Restructuring	(309)		(2,880)	0
Other	902	(3,449)	(2,973)	(3,929)
Net income including noncontrolling interests	61,293	46,066	114,824	225,206
Net income attributable to noncontrolling interests	4,481	4,844	8,012	10,316
Net income attributable to Parsons Corporation	56,812	41,222	106,812	214,890
Federal Solution Segment
Adjusted EBITDA attributable to Parsons Corporation
Adjusted EBITDA attributable to Parsons Corporation	50,359	45,556	126,658	101,052
Critical Infrastructure
Adjusted EBITDA attributable to Parsons Corporation
Adjusted EBITDA attributable to Parsons Corporation	$ 33,976	$ 38,006	$ 102,177	$ 80,296

Segment Information - Summary_3

Segment Information - Summary of Adjusted EBITDA Business Segment Information (Parenthetical) (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2019	Sep. 28, 2018
Segment Reporting Information [Line Items]
Reversal of accrued liability	$ 0	$ 0	$ 129,674
Revenue
Segment Reporting Information [Line Items]
Reversal of accrued liability			55,100
Other Income
Segment Reporting Information [Line Items]
Reversal of accrued liability			$ 74,600

Segment Information - Summary_4

Segment Information - Summary of Revenues and Property and Equipment, Net by Geographic Area (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 28, 2018	Sep. 30, 2019	Sep. 28, 2018	Dec. 31, 2018
Segment Reporting Information [Line Items]
Revenues	$ 1,023,277	$ 976,157	$ 2,917,424	$ 2,631,568
Property and Equipment, Net	109,238		109,238		$ 91,849
North America
Segment Reporting Information [Line Items]
Revenues	849,839	805,320	2,400,124	2,131,562
Property and Equipment, Net	103,690		103,690		86,847
Middle East
Segment Reporting Information [Line Items]
Revenues	169,028	164,677	504,604	485,377
Property and Equipment, Net	5,548		5,548		$ 5,002
Rest of World
Segment Reporting Information [Line Items]
Revenues	$ 4,410	$ 6,160	$ 12,696	$ 14,629

Segment Information - Summary_5

Segment Information - Summary of Revenues by Business Lines (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 28, 2018	Sep. 30, 2019	Sep. 28, 2018
Segment Reporting Information [Line Items]
Revenues	$ 1,023,277	$ 976,157	$ 2,917,424	$ 2,631,568
Federal Solution Segment
Segment Reporting Information [Line Items]
Revenues	486,175	443,725	1,387,484	1,076,125
Federal Solution Segment | Cyber & Intelligence
Segment Reporting Information [Line Items]
Revenues	90,429	68,895	247,710	177,838
Federal Solution Segment | Defense
Segment Reporting Information [Line Items]
Revenues	144,160	133,259	425,603	297,318
Federal Solution Segment | Mission Solutions
Segment Reporting Information [Line Items]
Revenues	87,936	122,780	237,914	280,902
Federal Solution Segment | Engineered Systems
Segment Reporting Information [Line Items]
Revenues	129,989	118,791	367,542	320,067
Federal Solution Segment | Geospatial
Segment Reporting Information [Line Items]
Revenues	33,661	0	108,715	0
Critical Infrastructure
Segment Reporting Information [Line Items]
Revenues	537,102	532,432	1,529,940	1,555,443
Critical Infrastructure | Connected Communities
Segment Reporting Information [Line Items]
Revenues	151,779	165,529	459,277	491,444
Critical Infrastructure | Mobility Solutions
Segment Reporting Information [Line Items]
Revenues	286,199	300,523	836,779	894,796
Critical Infrastructure | Industrial
Segment Reporting Information [Line Items]
Revenues	$ 99,124	$ 66,380	$ 233,884	$ 169,203

Subsequent Events - Additional

Subsequent Events - Additional Information (Details) - Employee Stock Ownership Plan (“ESOP”) - Subsequent Event - Common Stock $ in Millions	Oct. 14, 2019USD ($)shares
Subsequent Event [Line Items]
Repurchase of common stock, shares | shares	157,100
Repurchase of common stock | $	$ 5.4