Leases, Remaining Minimum Lease Payments (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Operating Leases
Year one	$ 324	$ 376
Year two	231	250
Year three	194	194
Year four	155	160
Year five	107	125
Thereafter	435	498
Total undiscounted lease payments	1,446	1,603
Less: Amount associated with discounting	276	313
Total lease liabilities	1,170	1,290
Finance Leases
Year one	187	88
Year two	182	86
Year three	187	87
Year four	178	91
Year five	178	82
Thereafter	1,498	1,011
Total undiscounted lease payments	2,410	1,445
Less: Amount associated with discounting	746	654
Total lease liabilities	$ 1,664	$ 791