Segment Information - Summary of Adjusted EBITDA Business Segment Information (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Adjusted EBITDA attributable to Parsons Corporation
Adjusted EBITDA attributable to Parsons Corporation	$ 58,974	$ 68,275
Adjusted EBITDA attributable to noncontrolling interests	1,522	3,749
Depreciation and amortization	(32,409)	(30,591)
Interest expense, net	(3,794)	(7,815)
Income tax expense	(5,084)	(1,886)
Equity-based compensation income (expense)	7,721	(3,850)
Transaction-related costs	(12,011)	(9,355)
Restructuring income (expense)	33	(2,218)
Other	(581)	(2,923)
Net income including noncontrolling interests	14,371	13,386
Net income attributable to noncontrolling interests	1,398	3,645
Net income attributable to Parsons Corporation	12,973	9,741
Federal Solution Segment
Adjusted EBITDA attributable to Parsons Corporation
Adjusted EBITDA attributable to Parsons Corporation	31,617	40,599
Critical Infrastructure
Adjusted EBITDA attributable to Parsons Corporation
Adjusted EBITDA attributable to Parsons Corporation	$ 27,357	$ 27,676