Investments in and Advances to Joint Ventures - Summary of Financial Information for Consolidated 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
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
Net income attributable to noncontrolling interests	11,547	11,530	26,790	21,253
Consolidated Joint Ventures
Schedule Of Equity Method Investments [Line Items]
Current assets	464,312		464,312		426,633
Noncurrent assets	11,670		11,670		14,295
Total assets	475,982		475,982		440,928
Current liabilities	276,649		276,649		260,286
Noncurrent liabilities	3,299		3,299		5,132
Total liabilities	279,948		279,948		265,418
Total joint venture equity	196,034		196,034		$ 175,510
Revenue	186,731	167,253	388,748	328,737
Costs	163,287	143,808	334,435	285,406
Net income (loss) attributable to Parsons Corporation	23,444	23,445	54,313	43,331
Net income attributable to noncontrolling interests	$ 11,547	$ 11,530	$ 26,790	$ 21,253