Investments in and Advances to Joint Ventures - Summary of Financial Information for Unconsolidated Joint Ventures (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021	Dec. 31, 2021
Schedule Of Equity Method Investments [Line Items]
Current assets	$ 1,640,966		$ 1,632,351
Total assets	3,808,841		3,830,940
Current liabilities	1,008,855		1,030,784
Total liabilities	1,858,216		1,893,828
Total joint venture equity	1,918,187		1,900,768
Investments in and advances to unconsolidated joint ventures	114,234		110,688
Revenue	949,069	$ 874,697
Costs	733,900	669,082
Net income attributable to Parsons Corporation	20,667	9,039
Equity in earnings of unconsolidated joint ventures	5,598	7,530
Unconsolidated Joint Ventures
Schedule Of Equity Method Investments [Line Items]
Current assets	1,707,836		1,620,735
Noncurrent assets	539,798		531,261
Total assets	2,247,634		2,151,996
Current liabilities	1,252,393		1,088,985
Noncurrent liabilities	603,929		669,911
Total liabilities	1,856,322		1,758,896
Total joint venture equity	391,312		393,100
Investments in and advances to unconsolidated joint ventures	114,234		$ 110,688
Revenue	384,581	236,517
Costs	373,286	210,847
Net income attributable to Parsons Corporation	11,295	25,670
Equity in earnings of unconsolidated joint ventures	$ 5,598	$ 7,530