Leases - Lease Cost (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Leases [Abstract]
Operating lease cost	$ 1,662	$ 1,149	$ 3,218	$ 2,217
Finance lease cost: amortization of lease assets	2,489	2,029	4,945	3,923
Finance lease cost: interest on lease liabilities	119	156	251	320
Finance lease cost	2,608	2,185	5,196	4,243
Variable lease cost	415	294	763	558
Total lease cost	$ 4,685	$ 3,628	$ 9,177	$ 7,018