Earnings Per Share - Net Income Available to Shareholders to Compute Basic and Diluted EPS (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Earnings Per Share [Abstract]
Net income attributable to Parsons Corporation	$ 20,667	$ 9,039
Convertible senior notes if-converted method interest adjustment	540	528
Diluted net income attributable to Parsons Corporation	$ 21,207	$ 9,567