Fair Value Disclosures - Rollforward of Level 3 Assets and Liabilities (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Trading and equity securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	$ 11	$ 0	$ 3	$ 0
Included in earnings	0	0	0	0
Included in unrealized net holding gains (losses) in OCI	0	0	0	0
Purchases	0	1	15	1
Issuances	0	0	0	0
Sales	(11)	(1)	(18)	(1)
Settlements	0	0	0	0
Transfers into Level 3	0		0
Ending balance	0	0	0	0
Change in unrealized gains (losses) included in earnings for the period, attributable to assets and liabilities still held	0		0
Non-agency MBS
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	386	441	391	432
Included in earnings	(7)	7	(5)	6
Included in unrealized net holding gains (losses) in OCI	11	(9)	12	14
Purchases	0	0	0	0
Issuances	0	0	0	0
Sales	0	0	0	0
Settlements	(8)	(14)	(16)	(27)
Transfers into Level 3	0		0
Ending balance	382	425	382	425
Change in unrealized gains (losses) included in earnings for the period, attributable to assets and liabilities still held	(7)		(5)
MSRs
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	1,036	1,119	1,108	1,056
Included in earnings	(51)	23	(105)	91
Included in unrealized net holding gains (losses) in OCI	0	0	0	0
Purchases	0	0	0	0
Issuances	30	46	52	83
Sales	0	0	0	0
Settlements	(45)	(45)	(85)	(87)
Transfers into Level 3	0		0
Ending balance	970	1,143	970	1,143
Change in unrealized gains (losses) included in earnings for the period, attributable to assets and liabilities still held	(51)		(105)
Net Derivatives
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	7	7	12	3
Included in earnings	13	1	21	1
Included in unrealized net holding gains (losses) in OCI	0	0	0	0
Purchases	0	0	0	0
Issuances	17	11	34	6
Sales	0	0	0	0
Settlements	(20)	(15)	(50)	(6)
Transfers into Level 3	(10)		(10)
Ending balance	7	4	7	4
Change in unrealized gains (losses) included in earnings for the period, attributable to assets and liabilities still held	17		18
Private Equity Investments
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	388	400	393	404
Included in earnings	1	5	24	11
Included in unrealized net holding gains (losses) in OCI	0	0	0	0
Purchases	61	3	68	27
Issuances	0	0	0	0
Sales	(1)	0	(34)	(24)
Settlements	0	(9)	(2)	(19)
Transfers into Level 3	0		0
Ending balance	449	$ 399	449	$ 399
Change in unrealized gains (losses) included in earnings for the period, attributable to assets and liabilities still held	$ 0		$ 4

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

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-Publisher FASB
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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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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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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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Amount of transfer of financial instrument classified as an asset into level 3 of the fair value hierarchy.

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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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