Investments in and Advances to Joint Ventures - Summary of Financial Information for Consolidated Joint Ventures (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Schedule Of Equity Method Investments [Line Items]
Current assets	$ 1,601,972		$ 1,526,409
Total assets	3,488,605		3,450,368
Current liabilities	1,151,324		1,144,382
Total liabilities	1,821,226		1,789,612
Total joint venture equity	1,635,262		1,629,890
Revenue	970,993	$ 904,405
Costs	769,632	714,237
Net income attributable to Parsons Corporation	12,973	9,741
Net income attributable to noncontrolling interests	1,398	3,645
Consolidated Joint Ventures
Schedule Of Equity Method Investments [Line Items]
Current assets	284,357		255,167
Noncurrent assets	2,441		2,860
Total assets	286,798		258,027
Current liabilities	219,880		193,583
Total liabilities	219,880		193,583
Total joint venture equity	66,918		$ 64,444
Revenue	100,278	115,104
Costs	97,150	107,206
Net income attributable to Parsons Corporation	3,128	7,898
Net income attributable to noncontrolling interests	$ 1,398	$ 3,645