Leases - Lease Cost (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Leases [Abstract]
Operating lease cost	$ 1,911	$ 1,334	$ 5,129	$ 3,551
Finance lease cost:
Amortization of lease assets	2,497	2,200	7,442	6,123
Interest on lease liabilities	114	154	365	474
Finance lease cost	2,611	2,354	7,807	6,597
Variable lease cost	372	308	1,135	866
Total lease cost	$ 4,894	$ 3,996	$ 14,071	$ 11,014