Segment Information - Summary of Adjusted EBITDA Business Segment Information (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Adjusted EBITDA attributable to Parsons Corporation
Adjusted EBITDA attributable to Parsons Corporation	$ 72,805	$ 60,317	$ 143,758	$ 123,956
Adjusted EBITDA attributable to noncontrolling interests	4,609	5,410	7,904	10,470
Depreciation and amortization	(30,581)	(34,635)	(61,090)	(69,308)
Interest expense, net	(4,354)	(4,758)	(8,227)	(9,201)
Income tax expense	(5,732)	(3,838)	(13,851)	(9,213)
Equity-based compensation expense	(4,791)	(4,921)	(8,689)	(11,901)
Transaction-related costs	(9,525)	(4,086)	(11,923)	(6,732)
Restructuring expense		(73)	(213)	(150)
Other	349	(1,389)	(1,046)	(1,880)
Net income including noncontrolling interests	22,780	12,027	46,623	26,041
Net income attributable to noncontrolling interests	4,485	5,325	7,661	10,300
Net income attributable to Parsons Corporation	18,295	6,702	38,962	15,741
Federal Solution Segment
Adjusted EBITDA attributable to Parsons Corporation
Adjusted EBITDA attributable to Parsons Corporation	47,645	32,500	90,283	64,482
Critical Infrastructure
Adjusted EBITDA attributable to Parsons Corporation
Adjusted EBITDA attributable to Parsons Corporation	$ 25,160	$ 27,817	$ 53,475	$ 59,474