Schedule of Future Minimum Rental Payments for Operating Leases (Details) $ in Millions	Dec. 31, 2017 USD ($)
Minimum Rental Payments
2018	$ 129
2019	117
2020	108
2021	99
2022	86
Thereafter	215
Net minimum lease commitments	754
Minimum Sublease Income
2018	(1)
2019	(1)
2020	(1)
2021	(1)
2022	0
Thereafter	0
Net minimum lease commitments	(4)
Operating Leases, Net Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
2018	128
2019	116
2020	107
2021	98
2022	86
Thereafter	215
Net minimum lease commitments	$ 750