Fair Value Measurements - Reconciliation of Assets and Liabilities Measured at Recurring L3 Fair Value (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation
Beginning Balance	$ 1,190	$ 901	$ 991	$ 861
Included in earnings	(150)	(2)	(240)	(1)
Purchases/originations/acquisitions	59	45	345	81
Settlements	(25)	(15)	(37)	(17)
Transfers Into Level 3	11	32	26	37
Ending Balance	1,085	961	1,085	961
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	(136)	(12)	(224)	(25)
Residential Mortgage
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation
Beginning Balance	190	136	179	137
Included in earnings	(1)	(1)	(1)	(4)
Purchases/originations/acquisitions	0	0	0	0
Settlements	(8)	(5)	(12)	(8)
Transfers Into Level 3	11	32	26	37
Ending Balance	192	162	192	162
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	(1)	(1)	(1)	(4)
Servicing Contracts
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation
Beginning Balance	1,141	926	938	858
Included in earnings	(161)	(13)	(245)	16
Purchases/originations/acquisitions	59	46	346	85
Settlements	0	0	0	0
Transfers Into Level 3	0	0	0	0
Ending Balance	1,039	959	1,039	959
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	(127)	(13)	(196)	16
Interest Rate Contract
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation
Beginning Balance	2	4	(1)	3
Included in earnings	34	22	58	36
Purchases/originations/acquisitions	0	(1)	(1)	(4)
Settlements	(31)	(21)	(51)	(31)
Transfers Into Level 3	0	0	0	0
Ending Balance	5	4	5	4
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	14	12	25	12
Equity Contract
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation
Beginning Balance	(143)	(165)	(125)	(137)
Included in earnings	(22)	(10)	(52)	(49)
Purchases/originations/acquisitions	0	0	0	0
Settlements	14	11	26	22
Transfers Into Level 3	0	0	0	0
Ending Balance	(151)	(164)	(151)	(164)
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	$ (22)	$ (10)	$ (52)	$ (49)