Investments in and Advances to Joint Ventures - Summary of Financial Information for Unconsolidated Joint Ventures (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023	Dec. 31, 2023
Schedule Of Equity Method Investments [Line Items]
Current assets	$ 2,427,254		$ 2,137,526
Total assets	5,098,443		4,804,061
Current liabilities	1,353,703		1,410,884
Total liabilities	2,855,286		2,427,346
Total joint venture equity	2,149,668		2,287,211
Investments in and advances to unconsolidated joint ventures	145,043		128,204
Revenue	1,535,676	$ 1,173,466
Costs	1,210,827	917,188
Net (loss) income attributable to Parsons Corporation	(107,355)	25,553
Equity in losses of unconsolidated joint ventures	(2,060)	(5,840)
Unconsolidated Joint Ventures
Schedule Of Equity Method Investments [Line Items]
Current assets	1,620,565		1,607,953
Noncurrent assets	475,188		483,693
Total assets	2,095,753		2,091,646
Current liabilities	1,040,231		1,057,113
Noncurrent liabilities	509,299		518,647
Total liabilities	1,549,530		1,575,760
Total joint venture equity	546,223		515,886
Investments in and advances to unconsolidated joint ventures	145,043		$ 128,204
Revenue	473,532	349,157
Costs	476,750	359,395
Net (loss) income attributable to Parsons Corporation	(3,218)	(10,238)
Unconsolidated Joint Ventures
Schedule Of Equity Method Investments [Line Items]
Equity in losses of unconsolidated joint ventures	$ (2,060)	$ (5,840)