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Derivative Instruments and Hedging Activities - Hedged Items in Fair Value Hedging Relationship (Detail) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Hedged Items In Fair Value Hedging Relationship [Line Items]
Hedged Assets, Discontinued Fair Value Hedge, Cumulative Increase (Decrease)	$ 206
Amortized cost of closed prepayment assets		$ 5,900
Amortized cost of closed prepayable assets, designated hedged items		3,100
Hedged assets cumulative basis adjustment		75
Available-for-sale securities
Hedged Items In Fair Value Hedging Relationship [Line Items]
Carrying Amount of Assets	9,831	10,825
Hedged Assets, Fair Value Hedge, Cumulative Increase (Decrease)	629	300
Hedged Assets, Discontinued Fair Value Hedge, Cumulative Increase (Decrease)	206	52
Interest-bearing deposits
Hedged Items In Fair Value Hedging Relationship [Line Items]
Carrying Amount Of Liabilities	(12,865)	(14,310)
Hedged Liabilities, Fair Value Hedge, Cumulative Increase (Decrease)	(257)	(12)
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	(8,473)	(9,403)
Hedged Liabilities, Fair Value Hedge, Cumulative Increase (Decrease)	(208)	44
Hedged Liabilities, Discontinued Fair Value Hedge, Cumulative Increase (Decrease)	34	64
Senior and subordinated notes
Hedged Items In Fair Value Hedging Relationship [Line Items]
Carrying Amount Of Liabilities	(21,989)	(27,777)
Hedged Liabilities, Fair Value Hedge, Cumulative Increase (Decrease)	(1,425)	(458)
Hedged Liabilities, Discontinued Fair Value Hedge, Cumulative Increase (Decrease)	$ (700)	$ 324

X

- Definition

Amortized cost of closed prepayable assets designated in fair value hedges

+ References

No definition available.

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- Definition

Amortized cost of closed prepayment assets for LOLA hedging purpose

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- Definition

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

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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.

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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=121590274&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=121590274&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

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=121590274&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.

+ 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=121590274&loc=SL109999712-113959

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