Leases Maturity of Lease Liabilities (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Total lease obligations	$ 542	$ 627
Current operating lease liabilities	(306)	(353)
Finance lease, current maturities of long-term debt	(83)	(85)
Noncurrent operating lease liabilities	1,562	978
Finance lease, long-term debt less current maturities	459	$ 542
Operating Lease
2021	371
2022	253
2023	219
2024	193
2025	156
Thereafter	1,156
Total lease payments	2,348
Less imputed interest	(480)
Total lease obligations	1,868
Current operating lease liabilities	(306)
Noncurrent operating lease liabilities	1,562
Finance Lease
2021	102
2022	98
2023	94
2024	90
2025	74
Thereafter	156
Total lease payments	614
Less imputed interest	(72)
Total lease obligations	542
Finance lease, current maturities of long-term debt	(83)
Finance lease, long-term debt less current maturities	$ 459