Leasing Arrangements - Schedule of Lease Liability Maturity (Details) - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020
Operating Leases
Remainder of 2021	$ 1,085
2022	4,233
2023	4,017
2024	3,760
2025	3,380
Thereafter	14,661
Total lease payments	31,136
Less interest	4,023
Present value of lease liabilities	27,113
Less current obligation	3,606	$ 3,485
Long-term obligation at September 30, 2021	23,507	$ 18,000
Finance Leases
Remainder of 2021	107
2022	399
2023	337
2024	268
2025	149
Thereafter	111
Total lease payments	1,371
Less interest	70
Present value of lease liabilities	1,301
Less current obligation	393
Long-term obligation at September 30, 2021	$ 908