Leases Maturity of Lease Liabilities (Details) - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018
Current operating lease liabilities	$ 361	$ 0
Finance lease, current maturities of long-term debt	85
Noncurrent operating lease liabilities	1,150	$ 0
Finance lease, long-term debt less current maturities	630
Operating Lease
Remainder of 2019	316
2020	344
2021	212
2022	140
2023	109
Thereafter	750
Total lease payments	1,871
Less imputed interest	(360)
Total lease obligations	1,511
Current operating lease liabilities	361
Noncurrent operating lease liabilities	1,150
Finance Lease
Remainder of 2019	83
2020	109
2021	104
2022	101
2023	97
Thereafter	339
Total lease payments	833
Less imputed interest	(118)
Total lease obligations	715
Finance lease, current maturities of long-term debt	85
Finance lease, long-term debt less current maturities	$ 630