Investments in and Advances to Joint Ventures - Summary of Financial Information for Unconsolidated Joint Ventures (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Schedule Of Equity Method Investments [Line Items]
Current assets	$ 2,137,526	$ 1,719,783
Total assets	4,804,061	4,198,142
Current liabilities	1,410,884	1,108,119
Total liabilities	2,427,346	2,102,207
Total joint venture equity	2,287,211	2,043,570
Investments in and advances to unconsolidated joint ventures	128,204	107,425
Revenue	5,442,749	4,195,272	$ 3,660,771
Costs	4,236,735	3,248,550	2,807,950
Net income attributable to Parsons Corporation	161,149	96,664	64,072
Equity in (losses) earnings of unconsolidated joint ventures	(47,751)	16,347	36,862
Unconsolidated Joint Ventures
Schedule Of Equity Method Investments [Line Items]
Current assets	1,607,953	1,610,246
Noncurrent assets	483,693	491,658
Total assets	2,091,646	2,101,904
Current liabilities	1,057,113	1,255,297
Noncurrent liabilities	518,647	468,056
Total liabilities	1,575,760	1,723,353
Total joint venture equity	515,886	378,551
Investments in and advances to unconsolidated joint ventures	128,204	107,425
Revenue	2,313,420	2,406,407	2,709,305
Costs	2,310,114	2,325,472	2,536,403
Net income attributable to Parsons Corporation	3,306	80,935	172,902
Unconsolidated Joint Ventures
Schedule Of Equity Method Investments [Line Items]
Equity in (losses) earnings of unconsolidated joint ventures	$ (47,751)	$ 16,347	$ 36,862