Leases - Schedule of Maturities of Lease Liabilities (Details) - USD ($) $ in Millions	Jun. 30, 2019	Dec. 31, 2018
Operating Leases
Remaining six months of 2019	$ 100
2020	164
2021	125
2022	98
2023	75
Thereafter	272
Total lease payments	834
Less: Interest	95
Total lease obligations	739
Finance Leases
Remaining six months of 2019	2
2020	3
2021	3
2022	2
2023	2
Total lease payments	16
Less: Interest	3
Thereafter	4
Total lease obligations	$ 13
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