Earnings Per Share - Schedule of Numerator and Denominator used to Compute Basic and Diluted EPS (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands		3 Months Ended	12 Months Ended
Jan. 01, 2024	Dec. 31, 2024	Mar. 31, 2024	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Numerator for Basic and Diluted EPS:
Net income attributable to Parsons Corporation		$ 54,180	$ 39,750	$ 235,053	$ 161,149	$ 96,664
Convertible senior notes if-converted method interest adjustment	$ 2,800			2,932	2,291	2,176
Diluted net income attributable to Parsons Corporation			$ 42,500	$ 237,985	$ 163,440	$ 98,840
Denominator for Basic and Diluted EPS:
Basic weighted average number of shares outstanding				106,274	104,992	103,758
Dilutive effect of stock-based awards	1,500			1,778	1,173	808
Dilutive effect of warrants				494	0
Dilutive effect of convertible senior notes	6,800			3,628	8,917	8,917
Diluted weighted average number of shares outstanding			114,400	112,174	115,082	113,483
Earnings per share:
Basic		$ 0.51	$ 0.37	$ 2.21	$ 1.53	$ 0.93
Diluted earnings per share		$ 0.49	$ 0.37	$ 2.12	$ 1.42	$ 0.87

Denominator for basic and diluted EPS.

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