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Derivatives - Gains/(Losses) on Derivatives Associated with Interest Rate Risk Management Activities (Details) - Hedging Instruments And Hedged Items - USD ($) $ in Millions | 3 Months Ended | 9 Months Ended
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Sep. 30, 2021 | Sep. 30, 2020 | Sep. 30, 2021 | Sep. 30, 2020
Customer Interest Rate Contracts Hedging | Customer interest rate contracts |  |  |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |  |  |
Gains (losses) related to interest rate derivatives | $ (29) | $ (14) | $ (197) | $ 197
Customer Interest Rate Contracts Hedging | Offsetting upstream interest rate contracts |  |  |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |  |  |
Gains (losses) related to interest rate derivatives | 29 | 14 | 197 | (197)
Debt Hedging | Interest Rate Swap |  |  |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |  |  |
Gains (losses) related to interest rate derivatives | 0 | (1) | 0 | 3
Debt Hedging | Term Borrowings |  |  |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |  |  |
Gains/(Losses) related to term borrowings | $ 0 | $ 1 | $ 0 | $ (2)

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- Definition Gain Loss Related To Changes In Fair Value Of Term Borrowings Due To Interest Rate Risk + References No definition available. + Details
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- Definition Gains Losses Related To Interest Rate Derivatives + References No definition available. + Details
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