Investments in and Advances to Joint Ventures - Summary of Financial Information for Unconsolidated Joint Ventures (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023	Dec. 31, 2023
Schedule Of Equity Method Investments [Line Items]
Current assets	$ 2,573,702		$ 2,573,702		$ 2,137,526
Total assets	5,238,730		5,238,730		4,804,061
Current liabilities	1,426,948		1,426,948		1,410,884
Total liabilities	2,919,086		2,919,086		2,427,346
Total joint venture equity	2,218,510		2,218,510		2,287,211
Investments in and advances to unconsolidated joint ventures	157,243		157,243		128,204
Revenue	1,670,467	$ 1,356,486	3,206,143	$ 2,529,952
Costs	1,318,931	1,068,220	2,529,758	1,985,408
Net income (loss) attributable to Parsons Corporation	69,172	43,241	(38,183)	68,794
Equity in losses of unconsolidated joint ventures	(16,837)	75	(18,897)	(5,765)
Unconsolidated Joint Ventures
Schedule Of Equity Method Investments [Line Items]
Current assets	1,617,486		1,617,486		1,607,953
Noncurrent assets	462,319		462,319		483,693
Total assets	2,079,805		2,079,805		2,091,646
Current liabilities	970,590		970,590		1,057,113
Noncurrent liabilities	498,239		498,239		518,647
Total liabilities	1,468,829		1,468,829		1,575,760
Total joint venture equity	610,976		610,976		515,886
Investments in and advances to unconsolidated joint ventures	157,243		157,243		$ 128,204
Revenue	544,000	530,467	1,017,532	879,624
Costs	555,971	534,555	1,032,721	893,950
Net income (loss) attributable to Parsons Corporation	(11,971)	(4,088)	(15,189)	(14,326)
Unconsolidated Joint Ventures
Schedule Of Equity Method Investments [Line Items]
Equity in losses of unconsolidated joint ventures	$ (16,837)	$ 75	$ (18,897)	$ (5,765)