Land, Buildings, Equipment and Software, Net - Depreciation Expense, Operating Lease Rent Expense, Minimum Operating Lease Commitments (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Land, Buildings and Equipment, Net [Abstract]
Depreciation expense	$ 148	$ 136	$ 148
Operating lease rent expense	147	161	$ 157
Capital Leased Assets, Gross	9	$ 35
Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
2019	114
2020	88
2021	64
2022	50
2023	36
Thereafter	$ 27