Fair Value Measurements - Change in Fair Values of Level 3 Financial Instruments (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018
Other Investments [Member]
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Beginning of Period Balance	$ 7	$ 3
Gains (Losses) included in comprehensive income	0	0
Gains (Losses) Included in Earnings	4	0
Purchases	0	0
Sales	0	0
Settlements	0	0
Transfers Other	0	0
Transfers into Level 3	1	4
Transfers out of Level 3	0	0
End of Period Balance	12	7
Unrealized Gains (Losses) Included in Earnings	4	0
Other Investments [Member] \| Principal Direct Investments [Member]
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Beginning of Period Balance	1	13
Gains (Losses) included in comprehensive income	0	0
Gains (Losses) Included in Earnings	0	(1)
Purchases	0	5
Sales	0	(16)
Settlements	0	0
Transfers Other	0	0
Transfers into Level 3	0	0
Transfers out of Level 3	0	0
End of Period Balance	1	1
Unrealized Gains (Losses) Included in Earnings	0	0
Available-for-sale Securities [Member] \| Other Securities [Member]
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Beginning of Period Balance	20	20
Gains (Losses) included in comprehensive income	15	0
Gains (Losses) Included in Earnings	0	0
Purchases	0	0
Sales	0	0
Settlements	0	0
Transfers Other	0	0
Transfers into Level 3	0	0
Transfers out of Level 3	(24)	0
End of Period Balance	11	20
Unrealized Gains (Losses) Included in Earnings	0	0
Interest Rate [Member]
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Beginning of Period Balance	5	9
Gains (Losses) included in comprehensive income	0	0
Gains (Losses) Included in Earnings	3	(2)
Purchases	2	1
Sales	(1)	(2)
Settlements	0	0
Transfers Other	0	0
Transfers into Level 3	21	7
Transfers out of Level 3	(8)	(8)
End of Period Balance	22	5
Unrealized Gains (Losses) Included in Earnings	0	0
Credit [Member]
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Beginning of Period Balance	0	1
Gains (Losses) included in comprehensive income	0	0
Gains (Losses) Included in Earnings	(8)	(31)
Purchases	0	0
Sales	0	0
Settlements	0	30
Transfers Other	0	0
Transfers into Level 3	0	0
Transfers out of Level 3	0	0
End of Period Balance	(8)	0
Unrealized Gains (Losses) Included in Earnings	0	0
Other [Member]
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Beginning of Period Balance	3	3
Gains (Losses) included in comprehensive income	0	0
Gains (Losses) Included in Earnings	0	0
Purchases	0	0
Sales	0	0
Settlements	0	0
Transfers Other	2	0
Transfers into Level 3	0	0
Transfers out of Level 3	0	0
End of Period Balance	5	3
Unrealized Gains (Losses) Included in Earnings	0	0
Loans Held For Sale Fair Value [Member]
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Beginning of Period Balance	0	1
Gains (Losses) included in comprehensive income	0	0
Gains (Losses) Included in Earnings	0	0
Purchases	0	0
Sales	(1)	(1)
Settlements	0	0
Transfers Other	1	(1)
Transfers into Level 3	0	1
Transfers out of Level 3	0	0
End of Period Balance	0	0
Unrealized Gains (Losses) Included in Earnings	0	0
Loans Held For Investment Fair Value [Member]
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Beginning of Period Balance	3	2
Gains (Losses) included in comprehensive income	0	0
Gains (Losses) Included in Earnings	0	0
Purchases	0	0
Sales	0	0
Settlements	0	0
Transfers Other	1	1
Transfers into Level 3	0	0
Transfers out of Level 3	0	0
End of Period Balance	4	3
Unrealized Gains (Losses) Included in Earnings	$ 0	$ 0

Fair value measurement with unobservable inputs reconciliation recurring basis asset and liabilities value.

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- Definition

Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Other Transfers

+ References

No definition available.

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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)
-URI http://asc.fasb.org/extlink&oid=117815213&loc=d3e19207-110258

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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).

+ 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)(1a)
-URI http://asc.fasb.org/extlink&oid=117815213&loc=d3e19207-110258

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- Definition

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.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(2)
-URI http://asc.fasb.org/extlink&oid=117815213&loc=d3e19207-110258

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- Definition

Amount of purchases, (sales), issuances and (settlements) 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.

+ References

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- Definition

Amount of sale 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.

+ References

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- Definition

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

+ 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)(3)
-URI http://asc.fasb.org/extlink&oid=117815213&loc=d3e19207-110258

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- Definition

Amount of transfers of financial instrument classified as an asset out of level 3 of the fair value hierarchy.

+ 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)(3)
-URI http://asc.fasb.org/extlink&oid=117815213&loc=d3e19207-110258

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- Definition

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

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- Definition

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

+ References

No definition available.

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