Loans - Additional Information (Detail) (USD $)	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Dec. 31, 2012
Accounts, Notes, Loans and Financing Receivable [Line Items]
Value of loans transferred from LHFI to LHFS	$ 57,000,000	$ 429,000,000
Loans transferred from loans held for sale to loans	12,000,000	11,000,000
Loans held for investment sold	503,000,000	239,000,000
Gain (Loss) on Sales of Loans, Net	4,000,000	13,000,000
Loans and Leases Receivable, Impaired, Commitment to Lend	2,000,000		1,000,000
Guaranteed Student Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Percentage of Loan Portfolio Current	90.00%		89.00%
Federally Guaranteed Residential Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Percentage of Loan Portfolio Current	82.00%		83.00%
Accrual Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Modifications, Recorded Investment	2,400,000,000		2,400,000,000
Accruing TDRs current	96.00%		95.00%
Cross-Border Outstanding Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross, Foreign	748,000,000		562,000,000
Residential Mortgage | Risk Level, High
Accounts, Notes, Loans and Financing Receivable [Line Items]
Concentration of credit risk, maximum exposure	12,900,000,000		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		43,200,000,000
Maximum Exposure to Loss, Percent	35.00%		36.00%
Government guaranteed percent	9.00%		10.00%
Commitments to Extend Credit | Home Equity
Accounts, Notes, Loans and Financing Receivable [Line Items]
Concentration of credit risk, maximum exposure	11,600,000,000		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	8,700,000,000		9,200,000,000
Interest Only Loans | Risk Level, High
Accounts, Notes, Loans and Financing Receivable [Line Items]
Concentration of credit risk, maximum exposure	7,200,000,000		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	1,400,000,000		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	5,700,000,000		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