Fair Value Disclosures - Rollforward of Level 3 Assets and Liabilities (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2020	Mar. 31, 2019
Trading Assets
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	$ 0	$ 3
Included in earnings	0	0
Included in unrealized net holding gains (losses) in OCI	0	0
Purchases	0	15
Issuances	0	0
Sales	0	(7)
Settlements	0	0
Ending balance	0	11
Change in unrealized gains (losses) included in earnings for the period, attributable to assets and liabilities still held	0
Non-agency MBS
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	368	391
Included in earnings	3	2
Included in unrealized net holding gains (losses) in OCI	(64)	1
Purchases	0	0
Issuances	0	0
Sales	0	0
Settlements	(9)	(8)
Ending balance	298	386
Change in unrealized gains (losses) included in earnings for the period, attributable to assets and liabilities still held	3
MSRs
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	2,618	1,108
Included in earnings	(526)	(54)
Included in unrealized net holding gains (losses) in OCI	0	0
Purchases	0	0
Issuances	187	22
Sales	0	0
Settlements	(129)	(40)
Ending balance	2,150	1,036
Change in unrealized gains (losses) included in earnings for the period, attributable to assets and liabilities still held	(526)
Net Derivatives
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	19	12
Included in earnings	111	8
Included in unrealized net holding gains (losses) in OCI	0	0
Purchases	0	0
Issuances	155	17
Sales	0	0
Settlements	(142)	(30)
Ending balance	143	7
Change in unrealized gains (losses) included in earnings for the period, attributable to assets and liabilities still held	154
Private Equity Investments
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	440	393
Included in earnings	2	23
Included in unrealized net holding gains (losses) in OCI	0	0
Purchases	27	7
Issuances	0	0
Sales	0	(33)
Settlements	(21)	(2)
Ending balance	448	$ 388
Change in unrealized gains (losses) included in earnings for the period, attributable to assets and liabilities still held	$ 0

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(1)
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- Definition

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

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-Publisher FASB
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- Definition

Amount of issuances 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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Fair value 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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- Definition

Amount of unrealized gain (loss) recognized in income for derivative asset (liability) after deduction of derivative liability (asset), measured at fair value using unobservable input (level 3) and still held.

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