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Acquisitions - Narrative (Details) - USD ($) $ in Millions	Jun. 30, 2025	Jan. 16, 2025	Jan. 01, 2025
Project Management \| Turner & Townsend
Business Combination [Line Items]
Equity method investments in unconsolidated subsidiaries, variations in ownership percentage			70.00%
Industrious
Business Combination [Line Items]
Equity interest percentage		60.00%
Goodwill deductible amount	$ 392
Industrious \| Global Workplace Solutions
Business Combination [Line Items]
Equity interest percentage		100.00%
Turner & Townsend \| Project Management
Business Combination [Line Items]
Equity interest percentage			10.00%
Estimated based on discounted forecasted cash flows	$ 408