Leases - Maturities of Lease Liabilities (Details) $ in Millions	Sep. 30, 2019 USD ($)
Operating Leases
2019 (remaining three months)	$ 136
2020	453
2021	355
2022	305
2023	262
Thereafter	1,004
Total lease payments	2,515
Less: interest	(745)
Total	1,770
Less: current portion	(419)
Long-term portion	1,351
Finance Leases
2019 (remaining three months)	11
2020	36
2021	25
2022	23
2023	20
Thereafter	179
Total lease payments	294
Less: interest	(82)
Total	212
Less: current portion	(30)
Long-term portion	$ 182