Earnings Per Share - Schedule of Denominator and Numerator used to Compute Basic and Diluted EPS (Details) - USD ($) $ / shares in Units, $ in Thousands		3 Months Ended
Jan. 01, 2024	Mar. 31, 2025	Mar. 31, 2024
Numerator for Basic and Diluted EPS:
Net (loss) income attributable to Parsons Corporation		$ 66,203	$ 39,750
Convertible senior notes if-converted method interest adjustment	$ 2,800	54	2,766
Diluted net income attributable to Parsons Corporation		$ 66,257	$ 42,516
Denominator for Basic and Diluted EPS:
Basic weighted average number of shares outstanding		106,831	106,037,000
Dilutive effect of stock-based awards	1,500,000	1,637	1,502,000
Dilutive effect of warrants		440	21,000
Dilutive effect of convertible senior notes due 2025	6,800,000	2,118	6,802,000
Diluted weighted average number of shares outstanding		111,026	114,362,000
Earnings per share:
Basic		$ 0.62	$ 0.37
Diluted		$ 0.6	$ 0.37

Denominator for basic and diluted EPS.

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Amount of increase (decrease) to net income used for calculating diluted earnings per share (EPS), resulting from the assumed exercise of dilutive convertible securities excluding adjustments related to ESOP convertible preferred stock, stock options, and restrictive stock units.

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Additional shares included in the calculation of diluted EPS as a result of the potentially dilutive effect of call options and warrants using the treasury stock method.

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