Fair Value Measurements - Reconciliation of Assets and Liabilities Measured at Fair Value on a Recurring Basis Using Significant Unobservable Inputs (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation
Derivative assets	$ 3,169,000,000		$ 3,169,000,000		$ 2,862,000,000
Derivative liabilities	1,907,000,000		1,907,000,000		$ 1,072,000,000
Unrealized gains or losses included in other comprehensive income for instruments still held	0	$ 0	0	$ 0
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation
Balance, beginning of period	772,000,000	760,000,000	669,000,000	1,023,000,000
Total (losses) gains (realized/unrealized) included in earnings	(102,000,000)	(18,000,000)	(10,000,000)	(311,000,000)
Purchases/originations	156,000,000	66,000,000	211,000,000	135,000,000
Settlements	(49,000,000)	(63,000,000)	(103,000,000)	(109,000,000)
Transfers into Level 3	10,000,000	22,000,000	20,000,000	29,000,000
Balance, end of period	787,000,000	767,000,000	787,000,000	767,000,000
The amount of total gains (losses) for the period included in earnings attributable to the change in unrealized gains or losses relating to assets still held	(56,000,000)	31,000,000	58,000,000	(287,000,000)
Interest rate contracts | Level 3
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation
Derivative assets	39,000,000	98,000,000	39,000,000	98,000,000
Derivative liabilities	8,000,000	9,000,000	8,000,000	9,000,000
Servicing Rights
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation
Balance, beginning of period	784,000,000	685,000,000	656,000,000	993,000,000
Total (losses) gains (realized/unrealized) included in earnings	(122,000,000)	(70,000,000)	(50,000,000)	(448,000,000)
Purchases/originations	156,000,000	61,000,000	212,000,000	131,000,000
Settlements	0	0	0	0
Transfers into Level 3	0	0	0	0
Balance, end of period	818,000,000	676,000,000	818,000,000	676,000,000
The amount of total gains (losses) for the period included in earnings attributable to the change in unrealized gains or losses relating to assets still held	(56,000,000)	(23,000,000)	69,000,000	(331,000,000)
Interest rate contracts
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation
Balance, beginning of period	30,000,000	61,000,000	53,000,000	10,000,000
Total (losses) gains (realized/unrealized) included in earnings	57,000,000	83,000,000	91,000,000	186,000,000
Purchases/originations	0	5,000,000	(1,000,000)	4,000,000
Settlements	(56,000,000)	(60,000,000)	(112,000,000)	(111,000,000)
Transfers into Level 3	0	0	0	0
Balance, end of period	31,000,000	89,000,000	31,000,000	89,000,000
The amount of total gains (losses) for the period included in earnings attributable to the change in unrealized gains or losses relating to assets still held	37,000,000	85,000,000	40,000,000	93,000,000
Equity Derivatives
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation
Balance, beginning of period	(195,000,000)	(171,000,000)	(201,000,000)	(163,000,000)
Total (losses) gains (realized/unrealized) included in earnings	(37,000,000)	(29,000,000)	(50,000,000)	(51,000,000)
Purchases/originations	0	0	0	0
Settlements	19,000,000	17,000,000	38,000,000	31,000,000
Transfers into Level 3	0	0	0	0
Balance, end of period	(213,000,000)	(183,000,000)	(213,000,000)	(183,000,000)
The amount of total gains (losses) for the period included in earnings attributable to the change in unrealized gains or losses relating to assets still held	(37,000,000)	(29,000,000)	(50,000,000)	(51,000,000)
Residential Mortgage Loans
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation
Balance, beginning of period	153,000,000	185,000,000	161,000,000	183,000,000
Total (losses) gains (realized/unrealized) included in earnings	0	(2,000,000)	(1,000,000)	2,000,000
Purchases/originations	0	0	0	0
Settlements	(12,000,000)	(20,000,000)	(29,000,000)	(29,000,000)
Transfers into Level 3	10,000,000	22,000,000	20,000,000	29,000,000
Balance, end of period	151,000,000	185,000,000	151,000,000	185,000,000
The amount of total gains (losses) for the period included in earnings attributable to the change in unrealized gains or losses relating to assets still held	$ 0	$ (2,000,000)	$ (1,000,000)	$ 2,000,000