Fair Value Measurements - Reconciliation of Assets and Liabilities Measured at Recurring L3 Fair Value (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation
Beginning Balance	$ 1,085	$ 961	$ 991	$ 861
Included in earnings	(131)	(8)	(370)	(9)
Purchases/originations/acquisitions	41	58	385	139
Settlements	(35)	11	(71)	(6)
Transfers Into Level 3	3	15	28	52
Ending Balance	963	1,037	963	1,037
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	(118)	(19)	(368)	(54)
Residential Mortgage
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation
Beginning Balance	192	162	179	137
Included in earnings	0	(1)	(1)	(5)
Purchases/originations/acquisitions	0	0	0	0
Settlements	(11)	(4)	(22)	(12)
Transfers Into Level 3	3	15	28	52
Ending Balance	184	172	184	172
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	0	(1)	(1)	(5)
Servicing Contracts
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation
Beginning Balance	1,039	959	938	858
Included in earnings	(171)	(8)	(416)	8
Purchases/originations/acquisitions	42	59	388	144
Settlements	0	0	0	0
Transfers Into Level 3	0	0	0	0
Ending Balance	910	1,010	910	1,010
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	(131)	(8)	(329)	8
Interest Rate Contract
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation
Beginning Balance	5	4	(1)	3
Included in earnings	51	18	110	54
Purchases/originations/acquisitions	(1)	(1)	(3)	(5)
Settlements	(40)	(22)	(91)	(53)
Transfers Into Level 3	0	0	0	0
Ending Balance	15	(1)	15	(1)
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	24	7	25	9
Equity Contract
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation
Beginning Balance	(151)	(164)	(125)	(137)
Included in earnings	(11)	(17)	(63)	(66)
Purchases/originations/acquisitions	0	0	0	0
Settlements	16	37	42	59
Transfers Into Level 3	0	0	0	0
Ending Balance	(146)	(144)	(146)	(144)
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	$ (11)	$ (17)	$ (63)	$ (66)