Fair Value Measurements - Reconciliation of Assets and Liabilities Measured at Fair Value on a Recurring Basis Using Significant Unobservable Inputs (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation
Derivative assets	$ 3,499		$ 3,499		$ 1,655
Derivative liabilities	1,294		1,294		$ 741
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation
Beginning balance	760	$ 1,190	1,023	$ 991
Included in earnings	(18)	(150)	(311)	(240)
Purchases/originations	66	59	135	345
Settlements	(63)	(25)	(109)	(37)
Transfers into Level 3	22	11	29	26
Ending balance	767	1,085	767	1,085
The amount of total gains or losses for the period included in earnings attributable to the change in unrealized gains or losses relating to assets still held	31	(136)	(287)	(224)
Interest rate contracts | Level 3
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation
Derivative assets	98	14	98	14
Derivative liabilities	9	9	9	9
Residential Mortgage Loans
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation
Beginning balance	185	190	183	179
Included in earnings	(2)	(1)	2	(1)
Purchases/originations	0	0	0	0
Settlements	(20)	(8)	(29)	(12)
Transfers into Level 3	22	11	29	26
Ending balance	185	192	185	192
The amount of total gains or losses for the period included in earnings attributable to the change in unrealized gains or losses relating to assets still held	(2)	(1)	2	(1)
Servicing Rights
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation
Beginning balance	685	1,141	993	938
Included in earnings	(70)	(161)	(448)	(245)
Purchases/originations	61	59	131	346
Settlements	0	0	0	0
Transfers into Level 3	0	0	0	0
Ending balance	676	1,039	676	1,039
The amount of total gains or losses for the period included in earnings attributable to the change in unrealized gains or losses relating to assets still held	(23)	(127)	(331)	(196)
Interest rate contracts
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation
Beginning balance	61	2	10	(1)
Included in earnings	83	34	186	58
Purchases/originations	5	0	4	(1)
Settlements	(60)	(31)	(111)	(51)
Transfers into Level 3	0	0	0	0
Ending balance	89	5	89	5
The amount of total gains or losses for the period included in earnings attributable to the change in unrealized gains or losses relating to assets still held	85	14	93	25
Equity Derivatives
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation
Beginning balance	(171)	(143)	(163)	(125)
Included in earnings	(29)	(22)	(51)	(52)
Purchases/originations	0	0	0	0
Settlements	17	14	31	26
Transfers into Level 3	0	0	0	0
Ending balance	(183)	(151)	(183)	(151)
The amount of total gains or losses for the period included in earnings attributable to the change in unrealized gains or losses relating to assets still held	$ (29)	$ (22)	$ (51)	$ (52)