Leases - Maturities of Lease Liabilities (Details) $ in Millions	Sep. 30, 2019 USD ($)
Lessee, Operating Lease, Liability, Payment, Due [Abstract]
2019 (remaining three months)	$ 75
2020	277
2021	231
2022	199
2023	169
Thereafter	701
Total lease payments	1,652
Less: interest	(508)
Total	1,144
Less: current portion	(244)
Long-term portion	900
Finance Lease, Liability, Payment, Due [Abstract]
2019 (remaining three months)	6
2020	15
2021	16
2022	16
2023	16
Thereafter	165
Total lease payments	234
Less: interest	(74)
Total	160
Less: current portion	(7)
Long-term portion	$ 153