Leases - Operating and Finance Lease Liability Reconciliation (Details) - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020
Leases [Abstract]
Total operating lease liabilities	$ 61,591	$ 44,833
Total finance lease liabilities	26,618	30,437
Gross lease liabilities	88,209	75,270
Imputed interest - operating leases	(7,637)	(5,734)
Imputed interest - finance leases	(2,099)	(2,003)
Imputed interest	(9,736)	(7,737)
Present value of operating leases	53,954	39,099
Present value of finance leases	24,519	28,434
Present value of lease liabilities	$ 78,473	$ 67,533
Operating Lease, Liability, Current, Statement of Financial Position [Extensible List]	Accrued expenses and other	Accrued expenses and other
Finance Lease, Liability, Current, Statement of Financial Position [Extensible List]	Accrued expenses and other	Accrued expenses and other
Current portion of operating lease liabilities	$ (5,913)	$ (4,586)
Current portion of finance lease liabilities	(8,712)	(10,374)
Current portion of lease liabilities	(14,625)	(14,960)
Total long-term operating lease liabilities	48,041	34,513
Total long-term finance lease liabilities	15,807	18,060
Total long-term lease liabilities	$ 63,848	$ 52,573
Operating Lease, Liability, Noncurrent, Statement of Financial Position [Extensible List]	Total long-term lease liabilities	Total long-term lease liabilities
Finance Lease, Liability, Noncurrent, Statement of Financial Position [Extensible List]	Total long-term lease liabilities	Total long-term lease liabilities