Derivatives - Derivatives Associated With Interest Rate Risk Management Activities (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Customer interest rate contracts
Derivative Instruments, Gain (Loss) [Line Items]
Notional	$ 3,950	$ 2,698
Assets	207	66
Liabilities	7	7
Offsetting upstream interest rate contracts
Derivative Instruments, Gain (Loss) [Line Items]
Notional	3,950	2,698
Assets	2	3
Liabilities	17	4
Customer Interest Rate Contracts Hedging \| Hedging Instruments And Hedged Items \| Customer interest rate contracts
Derivative Instruments, Gain (Loss) [Line Items]
Notional	6,868	3,044
Assets	436	90
Liabilities	1	4
Customer Interest Rate Contracts Hedging \| Hedging Instruments And Hedged Items \| Offsetting upstream interest rate contracts
Derivative Instruments, Gain (Loss) [Line Items]
Notional	6,868	3,044
Assets	5	4
Liabilities	$ 35	10
Debt Hedging \| Hedging Instruments And Hedged Items \| Interest rate contracts
Derivative Instruments, Gain (Loss) [Line Items]
Notional		500
Liabilities		0
Debt Hedging \| Hedging Instruments And Hedged Items \| Par
Derivative Instruments, Gain (Loss) [Line Items]
Term borrowings		500
Debt Hedging \| Hedging Instruments And Hedged Items \| Cumulative fair value hedging adjustments
Derivative Instruments, Gain (Loss) [Line Items]
Term borrowings		(2)
Debt Hedging \| Hedging Instruments And Hedged Items \| Unamortized premium (discount) and issuance costs
Derivative Instruments, Gain (Loss) [Line Items]
Term borrowings		(1)
Debt Hedging \| Hedging Instruments And Hedged Items \| Term Borrowings
Derivative Instruments, Gain (Loss) [Line Items]
Term borrowings		$ 497

Amount of hedged item in hedging relationship. Excludes hedged asset or liability.

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

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- Definition

Nominal or face amount used to calculate payment on derivative.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 1B
-URI http://asc.fasb.org/extlink&oid=121590274&loc=SL5580258-113959

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 1A
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=121590274&loc=SL5579245-113959

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- Definition

Fair value as of the balance sheet date of interest rate derivative assets, which includes all such derivative instruments in hedging and nonhedging relationships that are recognized as assets.

+ References

No definition available.

+ Details

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- Definition

Fair value as of the balance sheet date of interest rate derivative liabilities, which includes all such derivative instruments in hedging and nonhedging relationships that are recognized as liabilities.

+ References

No definition available.

+ Details

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