Deposits and Borrowings - Additional Information (Detail) - USD ($) $ in Millions	9 Months Ended
Sep. 30, 2015	Dec. 31, 2014
Deposits And Borrowings [Line Items]
Securitized debt obligations	$ 15,656	$ 11,624
Issuance of securitized debt obligations	4,200
Maturities of secured debt	175
Senior and subordinated notes	21,773	18,684
Fair value hedging losses	386	179
Advances from Federal Home Loan Banks	4,300	17,300
Repayments of Unsecured Debt	1,600
Other Assets
Deposits And Borrowings [Line Items]
Investment in FHLB stock	1,400	$ 2,000
Senior notes \| Total unsecured senior debt
Deposits And Borrowings [Line Items]
Proceeds from issuance of unsecured debt	4,500
Senior notes \| Floating unsecured senior debt
Deposits And Borrowings [Line Items]
Proceeds from issuance of unsecured debt	700
Senior notes \| Fixed unsecured senior debt
Deposits And Borrowings [Line Items]
Proceeds from issuance of unsecured debt	$ 3,800

Debt Instrument, Fair Value Hedging Losses

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Deposits and borrowings.

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- Definition

Secured debt maturities over the period.

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No definition available.

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Amount of borrowings as of the balance sheet date from the Federal Home Loan Bank, which are primarily used to cover shortages in the required reserve balance and liquidity shortages.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 470

-Section 45

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Federal Home Loan Bank (FHLB) stock represents an equity interest in a FHLB. It does not have a readily determinable fair value because its ownership is restricted and it lacks a market (liquidity).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

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-SubTopic 325

-Section 45

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The cash inflow from amounts received from issuance of long-term debt that is wholly or partially secured by collateral. Excludes proceeds from tax exempt secured debt.

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-Publisher FASB

-Name Accounting Standards Codification

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The cash inflow from the issuance of long-term debt that is not secured by collateral. Excludes proceeds from tax exempt unsecured debt.

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-Publisher FASB

-Name Accounting Standards Codification

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The cash outflow to repay long-term debt that is not secured by collateral. Excludes repayments of tax exempt unsecured debt.

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Carrying value as of the balance sheet date, including the current and noncurrent portions, of collateralized debt obligations (with maturities initially due after one year or beyond the operating cycle, if longer). Such obligations include mortgage loans, chattel loans, and any other borrowings secured by assets of the borrower.

+ References

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-Publisher FASB

-Name Accounting Standards Codification

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Including the current and noncurrent portions, carrying value as of the balance sheet date of uncollateralized debt obligations (with maturities initially due after one year or beyond the operating cycle if longer).

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