Loans - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Accounts, Notes, Loans and Financing Receivable [Line Items]
Value of loans transferred from LHFI to LHFS	$ 3,695,000,000	$ 754,000,000	$ 346,000,000
Loans transferred from loans held for sale to loans	71,000,000	63,000,000	213,000,000
Loans held for investment sold	4,800,000,000	725,000,000
Gain (Loss) on Sales of Loans, Net	3,000,000	22,000,000
Loans Discharged but Not Reaffirmed in Chapter 7 Bankruptcy Moved to Nonaccrual	232,000,000
Loans and Leases Receivable, Impaired, Commitment to Lend	1,000,000	5,000,000
Guaranteed Student Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Student loan portfolio percentage current	89.00%	79.00%
Accrual Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accruing TDRs included in impaired loan balances	2,400,000,000	2,600,000,000
Accruing TDRs current	95.00%	93.00%
Cross-Border Outstanding Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Concentration of credit risk, maximum exposure	562,000,000	630,000,000
Residential Mortgage | Risk Level, High
Accounts, Notes, Loans and Financing Receivable [Line Items]
Concentration of credit risk, maximum exposure	13,300,000,000	14,700,000,000
Residential Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Concentration of credit risk, maximum exposure	43,200,000,000	46,700,000,000
Maximum Exposure to Loss, Percent	36.00%	38.00%
Government guaranteed percent	10.00%	14.00%
Commitments to Extend Credit | Home Equity
Accounts, Notes, Loans and Financing Receivable [Line Items]
Concentration of credit risk, maximum exposure	11,700,000,000	12,700,000,000
Loan Origination Commitments | Mortgage Loans on Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Concentration of credit risk, maximum exposure	9,200,000,000	7,800,000,000
Interest Only Loans | Risk Level, High
Accounts, Notes, Loans and Financing Receivable [Line Items]
Concentration of credit risk, maximum exposure	7,600,000,000	9,400,000,000
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	1,500,000,000	1,900,000,000
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	5,300,000,000
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
Newly designated troubled debt restructuring [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans Discharged but Not Reaffirmed in Chapter 7 Bankruptcy Moved to Nonaccrual	24,000,000
Newly designated nonaccrual troulbed debt restructuring [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans Discharged but Not Reaffirmed in Chapter 7 Bankruptcy Moved to Nonaccrual	$ 177,000,000