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, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021	Dec. 31, 2021
Schedule Of Equity Method Investments [Line Items]
Current assets	$ 1,583,626		$ 1,583,626		$ 1,632,351
Total assets	4,109,805		4,109,805		3,830,940
Current liabilities	1,098,786		1,098,786		1,030,784
Total liabilities	2,145,138		2,145,138		1,893,828
Total joint venture equity	1,928,181		1,928,181		1,900,768
Investments in and advances to unconsolidated joint ventures	115,478		115,478		110,688
Revenue	1,008,721	$ 879,356	1,957,790	$ 1,754,053
Costs	781,772	680,328	1,515,672	1,349,410
Net income attributable to Parsons Corporation	18,295	6,702	38,962	15,741
Equity in earnings of unconsolidated joint ventures	5,613	9,428	11,211	16,958
Unconsolidated Joint Ventures
Schedule Of Equity Method Investments [Line Items]
Current assets	1,670,402		1,670,402		1,620,735
Noncurrent assets	523,440		523,440		531,261
Total assets	2,193,842		2,193,842		2,151,996
Current liabilities	1,283,227		1,283,227		1,088,985
Noncurrent liabilities	496,487		496,487		669,911
Total liabilities	1,779,714		1,779,714		1,758,896
Total joint venture equity	414,128		414,128		393,100
Investments in and advances to unconsolidated joint ventures	115,478		115,478		$ 110,688
Revenue	594,959	736,284	979,540	972,801
Costs	564,239	696,198	937,525	907,045
Net income attributable to Parsons Corporation	30,720	40,086	42,015	65,756
Equity in earnings of unconsolidated joint ventures	$ 5,613	$ 9,428	$ 11,211	$ 16,958