Derivative Instruments Derivatives 2 - FV Gains and Losses (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Fair Value Gain (Loss) on Derivative, Net	$ 1,148	$ (1,365)
Net contractual interest expense on interest-rate swaps	6,742	5,347
Interest and Dividend Income, Operating	23,562	29,426
Long-term debt	(16,817)	(23,977)
Change in Unrealized Gain (Loss) on Hedged Item in Fair Value Hedge	0	22
Hedged Asset, Fair Value Hedge	83,521
Hedged Liability, Fair Value Hedge	(55,345)
Hedged Liability, Fair Value Hedge, Cumulative Increase (Decrease)	1,182
Hedged Asset, Discontinued Fair Value Hedge, Cumulative Increase (Decrease)	(36)
Interest and Fee Income, Loans and Leases	23,353	28,938
Hedged Asset, Fair Value Hedge, Cumulative Increase (Decrease)	(36)
Hedged Asset, Fair Value Hedge, Last-of-Layer, Cumulative Increase (Decrease)	55,819
Hedged Asset, Fair Value Hedge, Last-of-Layer, Amount	2,879
Hedged Liability, Discontinued Fair Value Hedge, Cumulative Increase (Decrease)	1,182
Pay-fixed Swap
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Fair Value Gain (Loss) on Derivative, Net	2,207	(4,029)
Receive-fixed Swap
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Fair Value Gain (Loss) on Derivative, Net	(1,855)	3,343
Basis Swap
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Fair Value Gain (Loss) on Derivative, Net	(46)	56
Foreign Currency Swap
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Fair Value Gain (Loss) on Derivative, Net	(8)	(38)
Pay-fixed Swaption
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Fair Value Gain (Loss) on Derivative, Net	107	(148)
Receive-fixed Swaption
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Fair Value Gain (Loss) on Derivative, Net	(239)	632
Future [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Fair Value Gain (Loss) on Derivative, Net	1	(71)
Risk Management Derivatives
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Fair Value Gain (Loss) on Derivative, Net	156	(361)
Net contractual interest expense on interest-rate swaps	(11)	(106)
Mortgage commitment derivatives
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Fair Value Gain (Loss) on Derivative, Net	1,082	(993)
Other
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Fair Value Gain (Loss) on Derivative, Net	(90)	$ (11)
Interestrateriskonheldforinvestmentmortgageloantrust | Interest Income
Derivative Instruments, Gain (Loss) [Line Items]
Change in Unrealized Gain (Loss) on Hedged Item in Fair Value Hedge	(36)
Interestrateriskonheldforinvestmentmortgageloan | Interest Income
Derivative Instruments, Gain (Loss) [Line Items]
Change in Unrealized Gain (Loss) on Fair Value Hedging Instruments	36
Interestrateriskondebt | Interest Expense
Derivative Instruments, Gain (Loss) [Line Items]
Change in Unrealized Gain (Loss) on Hedged Item in Fair Value Hedge	1,195
Discontinued hedge related basis adjustment amortization	(13)
Change in Unrealized Gain (Loss) on Fair Value Hedging Instruments	(1,214)
Interest accruals on hedging instruments	$ 54