Leases - Schedule of Maturities of Lease Liabilities (Details) - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018
Operating Leases
Remaining nine months of 2019	$ 142
2020	155
2021	116
2022	89
2023	70
Thereafter	255
Total lease payments	827
Less: Interest	93
Total lease obligations	734
Finance Leases
Remaining nine months of 2019	3
2020	3
2021	3
2022	2
2023	2
Total lease payments	17
Less: Interest	5
Thereafter	4
Total lease obligations	$ 12
Operating Leases
2019		$ 207
2020		157
2021		116
2022		93
2023		76
Thereafter		244
Capital Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
2019		3
2020		3
2021		1
2022		1
2023		1
Beyond 2023		$ 3