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Fixed Assets - Summary of Fixed Assets (Detail) - USD ($) $ in Millions | Dec. 31, 2021 | Dec. 31, 2020
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Property Plant And Equipment Useful Life And Values [Abstract] |  |
Office equipment | $ 36.2 | $ 33.0
Furniture and fixtures | 137.1 | 138.3
Leasehold improvements | 170.8 | 166.0
Computer equipment | 247.1 | 214.2
Land and buildings - corporate headquarters | 145.3 | 145.1
Software | 532.2 | 452.2
Other | 17.2 | 16.7
Work in process | 23.0 | 14.1
Gross fixed assets | 1,308.9 | 1,179.6
Accumulated depreciation | (808.1) | (728.9)
Net fixed assets | $ 500.8 | $ 450.7

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