Earnings Per Share - Net Income Available to Shareholders to Compute Basic and Diluted EPS (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Earnings Per Share [Abstract]
Net income attributable to Parsons Corporation	$ 18,295	$ 6,702	$ 38,962	$ 15,741
Convertible senior notes if-converted method interest adjustment	542	531	1,082	1,059
Diluted net income attributable to Parsons Corporation	$ 18,837	$ 7,233	$ 40,044	$ 16,800