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
Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation
Derivative assets	$ 2,478		$ 2,862
Derivative liabilities	1,226		$ 1,072
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation
Beginning balance	669	$ 1,023
Total gains (losses) (realized/unrealized) included in earnings	92	(293)
Purchases/originations	56	69
Settlements	(54)	(46)
Transfers into Level 3	9	7
Ending balance	772	760
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	153	(289)
Interest rate contracts \| Level 3
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation
Derivative assets	39	69
Derivative liabilities	9	8
Servicing Rights
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation
Beginning balance	656	993
Total gains (losses) (realized/unrealized) included in earnings	71	(378)
Purchases/originations	57	70
Settlements	0	0
Transfers into Level 3	0	0
Ending balance	784	685
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	138	(341)
Interest rate contracts
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation
Beginning balance	53	10
Total gains (losses) (realized/unrealized) included in earnings	35	103
Purchases/originations	(1)	(1)
Settlements	(57)	(51)
Transfers into Level 3	0	0
Ending balance	30	61
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	70
Equity Derivatives
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation
Beginning balance	(201)	(163)
Total gains (losses) (realized/unrealized) included in earnings	(13)	(22)
Purchases/originations	0	0
Settlements	19	14
Transfers into Level 3	0	0
Ending balance	(195)	(171)
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	(13)	(22)
Residential Mortgage Loans
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation
Beginning balance	161	183
Total gains (losses) (realized/unrealized) included in earnings	(1)	4
Purchases/originations	0	0
Settlements	(16)	(9)
Transfers into Level 3	9	7
Ending balance	153	185
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)	$ 4

Fair value, after the effects of master netting arrangements, of a financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes assets not subject to a master netting arrangement and not elected to be offset.

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Fair value, after the effects of master netting arrangements, of a financial liability or contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes liabilities not subject to a master netting arrangement and not elected to be offset.

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Amount of unrealized gain (loss) recognized in income from asset measured at fair value on recurring basis using unobservable input (level 3) and still held.

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Amount of gain (loss) recognized in income from asset measured at fair value on recurring basis using unobservable input (level 3).

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Amount of purchases of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

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