Earnings Per Share - Schedule of Denominator and Numerator used to Compute Basic and Diluted EPS (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Numerator for Basic and Diluted EPS:
Net income attributable to Parsons Corporation	$ (107,355)	$ 25,553
Convertible senior notes if-converted method interest adjustment	0	551
Diluted net income attributable to Parsons Corporation	$ (107,355)	$ 26,104
Denominator for Basic and Diluted EPS:
Basic weighted average number of shares outstanding	106,037	104,805
Dilutive effect of stock-based awards	0	1,032
Dilutive effect of convertible senior notes due 2025	0	8,917
Diluted weighted average number of shares outstanding	106,037	114,754
Earnings per share:
Basic	$ (1.01)	$ 0.24
Diluted	$ (1.01)	$ 0.23