Segment Information - Additional Information (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2026 USD ($) Segment	Mar. 31, 2025 USD ($)	Dec. 31, 2025 USD ($)
Segment Reporting Information [Line Items]
Number of reportable segments \| Segment	2
Revenues	$ 1,491,176	$ 1,554,360
Property and equipment, net	$ 154,586		$ 151,061
Segment Reporting, CODM, Individual Title and Position or Group Name [Extensible Enumeration]	srt:ChiefExecutiveOfficerMember
Segment Reporting, Expense Information Used by CODM, Description	The CODM evaluates segment operating performance using segment Revenue, segment direct cost of contracts, segment Selling, General and Administrative expense and segment Adjusted EBITDA attributable to Parsons Corporation.
Segment Reporting, CODM, Profit (Loss) Measure, How Used, Description	Adjusted EBITDA is the measure of our operating performance used by the CODM to assess our segments’ financial performance. The CODM uses Adjusted EBITDA for business planning purposes, including to manage our segments against internal projected results of operations and measure the performance of our segments generally.
United States
Segment Reporting Information [Line Items]
Revenues	$ 1,100,000	$ 1,200,000
Property and equipment, net	$ 133,600		$ 130,500

Amount, excluding tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer. Tax collected from customer is tax assessed by governmental authority that is both imposed on and concurrent with specific revenue-producing transaction, including, but not limited to, sales, use, value added and excise.

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+ Details

PARSONS CORP 10-Q