Other Financial Data - Components of Fixed Assets, Net (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Fixed Assets, net [Line Items]
Fixed assets, gross	$ 2,146	$ 2,136
Less: Accumulated depreciation	1,509	1,498
Fixed assets, net	637	638
Depreciation of fixed assets	183	167	$ 151
Software
Fixed Assets, net [Line Items]
Fixed assets, gross	981	983
Leasehold improvements
Fixed Assets, net [Line Items]
Fixed assets, gross	437	430
Furniture, fixtures and equipment
Fixed Assets, net [Line Items]
Fixed assets, gross	297	269
Computer equipment
Fixed Assets, net [Line Items]
Fixed assets, gross	271	294
Construction in progress
Fixed Assets, net [Line Items]
Fixed assets, gross	133	130
Other
Fixed Assets, net [Line Items]
Fixed assets, gross	$ 27	$ 30