Deposits and Borrowings - Additional Information (Detail) (USD $)	9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Dec. 31, 2013
Deposits And Borrowings [Line Items]
Securitized debt obligations	$ 10,508,000,000		$ 10,289,000,000
Issuance of securitized debt obligations	3,000,000,000
Maturities of Secured Debt	2,800,000,000
Debt maturities from credit card securitization trusts	2,808,000,000	3,304,000,000
Senior and subordinated notes	18,534,000,000		13,134,000,000
Fair value hedging losses	33,000,000		8,000,000
Repayments of unsecured debt	2,375,000,000	500,000,000
Advances from Federal Home Loan Banks	10,900,000,000		16,300,000,000
Other Assets [Member]
Deposits And Borrowings [Line Items]
Investment in FHLB stock	1,700,000,000		1,900,000,000
Senior notes | Total unsecured senior debt
Deposits And Borrowings [Line Items]
Proceeds from issuance of unsecured debt	7,800,000,000
Senior notes | Floating unsecured senior debt
Deposits And Borrowings [Line Items]
Proceeds from issuance of unsecured debt	250,000,000
Senior notes | Fixed unsecured senior debt
Deposits And Borrowings [Line Items]
Proceeds from issuance of unsecured debt	$ 7,500,000,000