Segment Information - Summary of Adjusted EBITDA Business Segment Information (Details) - USD ($) $ in Thousands	3 Months Ended			6 Months Ended
	Jun. 30, 2024	Mar. 31, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Adjusted EBITDA attributable to Parsons Corporation
Adjusted EBITDA attributable to Parsons Corporation	$ 138,393		$ 106,576	$ 263,897	$ 187,081
Adjusted EBITDA attributable to noncontrolling interests	11,837		11,730	27,426	21,616
Depreciation and amortization	(24,440)		(28,689)	(48,971)	(57,048)
Interest expense, net	(9,183)		(6,993)	(21,029)	(12,658)
Income tax (expense) benefit	(22,415)		(15,223)	9,819	(26,726)
Equity-based compensation expense	(10,647)		(9,314)	(23,303)	(16,017)
Loss on extinguishment of debt	0	$ (211,000)	0	(211,018)	0
Transaction-related costs	(2,302)		(1,917)	(5,188)	(3,535)
Restructuring expense	0		0	0	(546)
Other	(524)		(1,399)	(3,026)	(2,120)
Net income (loss) including noncontrolling interests	80,719		54,771	(11,393)	90,047
Net income attributable to noncontrolling interests	11,547		11,530	26,790	21,253
Net income (loss) attributable to Parsons Corporation	69,172		43,241	(38,183)	68,794
Federal Solution Segment
Adjusted EBITDA attributable to Parsons Corporation
Adjusted EBITDA attributable to Parsons Corporation	102,781		85,640	195,322	141,788
Critical Infrastructure
Adjusted EBITDA attributable to Parsons Corporation
Adjusted EBITDA attributable to Parsons Corporation	35,612		20,936	68,575	45,293
Net income (loss) attributable to Parsons Corporation	$ 0		$ (410)	$ (6,677)	$ (803)