Leases - Operating Lease Income and Related Depreciation Expense (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, Lease Income, Statement of Income or Comprehensive Income [Extensible Enumeration]	Noninterest Income, Other	Noninterest Income, Other	Noninterest Income, Other	Noninterest Income, Other
Operating lease income	$ 1,190	$ 1,425	$ 3,792	$ 4,236
Depreciation expense	$ 785	$ 1,035	$ 2,595	$ 3,261