Leases - Schedule of Maturities of Lease Liabilities (Details) - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018
Operating Leases
Remaining three months of 2019	$ 50
2020	173
2021	134
2022	105
2023	82
Thereafter	303
Total lease payments	847
Less: Interest	97
Total lease obligations	750
Finance Leases
Remaining three months of 2019	1
2020	3
2021	2
2022	2
2023	1
Total lease payments	13
Less: Interest	2
Thereafter	4
Total lease obligations	$ 11
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