Leases - Summary of Maturities of Lease Liabilities (Details) $ in Millions	Mar. 31, 2019 USD ($)
Operating Leases
2019	$ 108
2020	139
2021	123
2022	108
2023	93
Thereafter	332
Total lease payments	903
Less imputed interest	116
Total	787
Finance Leases
2019	2
2020	3
2021	3
2022	3
2023	2
Thereafter	5
Total lease payments	18
Less imputed interest	3
Total	15
2019	110
2020	142
2021	126
2022	111
2023	95
Thereafter	337
Total lease payments	921
Less imputed interest	119
Total	$ 802