Leases Lease-Related Assets and Liabilities (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Operating lease right-of-use assets	$ 1,892	$ 1,349
Finance lease right-of-use assets	667	779
Finance Lease, Right of Use Asset, Accumulated Depreciation	567	455
Total lease assets	2,559	2,128
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
Total lease liabilities	2,410	$ 1,958
Operating Lease
Current operating lease liabilities	306
Noncurrent operating lease liabilities	1,562
Finance Lease
Finance lease, current maturities of long-term debt	83
Finance lease, long-term debt less current maturities	$ 459