Loans - Additional Information (Detail) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Dec. 31, 2012
Accounts, Notes, Loans and Financing Receivable [Line Items]
Value of loans transferred from LHFI to LHFS	$ (87,000,000)	$ (687,000,000)	$ (144,000,000)	$ (1,116,000,000)
Transfer of Loans Held-for-sale to Portfolio Loans	5,000,000	20,000,000	17,000,000	31,000,000
Loans held for investment sold	159,000,000	907,000,000	662,000,000	1,000,000,000
Gain (Loss) on Sales of Loans, Net	3,000,000	30,000,000	7,000,000	36,000,000
Loans and Leases Receivable, Impaired, Commitment to Lend	3,000,000		3,000,000		1,000,000
Guaranteed Student Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Percentage of Loan Portfolio Current	87.00%		87.00%		89.00%
Residential Guaranteed [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Percentage of Loan Portfolio Current	82.00%		82.00%		83.00%
Accrual Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Modifications, Recorded Investment	2,700,000,000		2,700,000,000		2,400,000,000
Accruing TDRs current	96.00%		96.00%		95.00%
Cross-Border Outstanding Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross, Foreign	734,000,000		734,000,000		562,000,000
Residential Mortgage | Risk Level, High
Accounts, Notes, Loans and Financing Receivable [Line Items]
Concentration of credit risk, maximum exposure	12,600,000,000		12,600,000,000		13,300,000,000
Residential Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Concentration of credit risk, maximum exposure	42,300,000,000		42,300,000,000		43,200,000,000
Maximum Exposure to Loss, Percent	35.00%		35.00%		36.00%
Government guaranteed percent	9.00%		9.00%		10.00%
Commitments to Extend Credit | Home Equity
Accounts, Notes, Loans and Financing Receivable [Line Items]
Concentration of credit risk, maximum exposure	11,300,000,000		11,300,000,000		11,700,000,000
Loan Origination Commitments | Mortgage Loans on Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Concentration of credit risk, maximum exposure	8,600,000,000		8,600,000,000		9,200,000,000
Interest Only Loans | Risk Level, High
Accounts, Notes, Loans and Financing Receivable [Line Items]
Concentration of credit risk, maximum exposure	6,600,000,000		6,600,000,000		7,600,000,000
Interest Only Loans, High LTV First Lien and Junior Lien, With No Mortgage Insurance [Member] | Risk Level, High
Accounts, Notes, Loans and Financing Receivable [Line Items]
Concentration of credit risk, maximum exposure	1,300,000,000		1,300,000,000		1,500,000,000
Amortizing Loans, High LTV First Lien and Junior Lien, With No Mortgage Insurance [Member] | Risk Level, High
Accounts, Notes, Loans and Financing Receivable [Line Items]
Concentration of credit risk, maximum exposure	6,000,000,000		6,000,000,000		5,700,000,000
Commercial Portfolio Segment [Member] | Lower Limit
Accounts, Notes, Loans and Financing Receivable [Line Items]
Minimum amount of modified loan in a TDR to evaluate individually for impairment	$ 3,000,000		$ 3,000,000		$ 3,000,000