Derivative Instruments and Hedging Activities - Hedged Items in Fair Value Hedging Relationship (Details) - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020
Hedged Items In Fair Value Hedging Relationship [Line Items]
Hedged Assets, Fair Value Hedge, Cumulative Increase (Decrease)	$ (1)
Hedged Assets, Discontinued Fair Value Hedge, Cumulative Increase (Decrease)	249
Prepayable Financial Asset Closed Portfolio, Last-of-Layer, Amortized Cost	225
Available-for-sale securities
Hedged Items In Fair Value Hedging Relationship [Line Items]
Carrying Amount of Assets	9,914	$ 9,797
Hedged Assets, Fair Value Hedge, Cumulative Increase (Decrease)	381	590
Hedged Assets, Discontinued Fair Value Hedge, Cumulative Increase (Decrease)	152	200
Interest-bearing deposits
Hedged Items In Fair Value Hedging Relationship [Line Items]
Carrying Amount Of Liabilities	(7,951)	(11,312)
Hedged Liabilities, Fair Value Hedge, Cumulative Increase (Decrease)	(97)	(213)
Hedged Liabilities, Discontinued Fair Value Hedge, Cumulative Increase (Decrease)	0	0
Securitized debt obligations
Hedged Items In Fair Value Hedging Relationship [Line Items]
Carrying Amount Of Liabilities	(9,239)	(7,609)
Hedged Liabilities, Fair Value Hedge, Cumulative Increase (Decrease)	(31)	(171)
Hedged Liabilities, Discontinued Fair Value Hedge, Cumulative Increase (Decrease)	5	20
Senior and subordinated notes
Hedged Items In Fair Value Hedging Relationship [Line Items]
Carrying Amount Of Liabilities	(19,889)	(21,927)
Hedged Liabilities, Fair Value Hedge, Cumulative Increase (Decrease)	(774)	(1,282)
Hedged Liabilities, Discontinued Fair Value Hedge, Cumulative Increase (Decrease)	$ (561)	$ (666)

Carry amount of assets hedged in fair value hedging relationship

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- Definition

The carry amount of liabilities in fair value hedging relationship

+ References

No definition available.

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- Definition

[Line Items] for Table shows the carrying amount and associated cumulative basis adjustment related to the application of hedge accounting that is included in the carrying amount of hedged assets and liabilities in fair value hedging relationships.

+ References

No definition available.

+ Details

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- Definition

Amount of cumulative increase (decrease) in fair value of hedged asset in fair value hedge, attributable to hedged risk, remaining after discontinued hedge.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4EE
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=125515794&loc=SL109999712-113959

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- Definition

Amount of cumulative increase (decrease) in fair value of hedged asset in fair value hedge, attributable to hedged risk.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4EE
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=125515794&loc=SL109999712-113959

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- Definition

Amount of cumulative increase (decrease) in fair value of hedged liability in fair value hedge, attributable to hedged risk, remaining after discontinued hedge.

+ References

+ Details

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- Definition

Amount of cumulative increase (decrease) in fair value of hedged liability in fair value hedge, attributable to hedged risk.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4EE
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=125515794&loc=SL109999712-113959

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- Definition

Amortized cost of closed portfolio of prepayable financial asset, used to designate hedging relationship in which hedged item is last layer expected to be remaining at end of hedging relationship.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4EEE
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=125515794&loc=SL109999718-113959

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