Summary of Significant Accounting Policies - Land, Buildings, Equipment and Software and Leases (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Land, buildings, equipment and software
Land, buildings, equipment and software, net of accumulated depreciation	$ 590	$ 602
Accumulated depreciation	2,000	1,900
Depreciation and amortization expense	$ 144	$ 153	$ 147
Minimum
Land, buildings, equipment and software
Depreciation and amortization period	3 years
Leases
Lease renewal term	1 year
Maximum
Land, buildings, equipment and software
Depreciation and amortization period	39 years
Leases
Lease renewal term	20 years