Leases - Lease Cost (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Leases [Abstract]
Operating lease cost	$ 1,334	$ 934	$ 3,551	$ 2,644
Finance lease cost: amortization of lease assets	2,200	2,609	6,123	7,319
Finance lease cost: interest on lease liabilities	154	164	474	479
Finance lease cost	2,354	2,773	6,597	7,798
Variable lease cost	308	244	866	775
Total lease cost	$ 3,996	$ 3,951	$ 11,014	$ 11,217