Loans - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011	Dec. 31, 2011
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans transferred from loans held for sale to loans	$ 11	$ 5
Value of loans transferred from LHFI to LHFS	429	122
Loans held for investment sold	239	141
Gain on sale of loans held for investment	13	2
Commitments to lend additional funds to debtors owing receivables	5		5
Concentration of credit risk, maximum exposure, percentage of total loans	38.00%
Lower Limit
Accounts, Notes, Loans and Financing Receivable [Line Items]
Minimum amount of modified loan in a TDR to evaluate individually for impairment	4
Guaranteed Student Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Student loan portfolio percentage current	78.00%		79.00%
Accrual Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accruing TDRs included in impaired loan balances	2,600		2,576
Accruing TDRs current	94.00%		93.00%
Cross-Border Outstanding Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Concentration of credit risk, maximum exposure	660		630
Residential Mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Concentration of credit risk, maximum exposure, percentage of total loans			38.00%
Concentration of credit risk, maximum exposure	46,500		46,700
Government guaranteed percent	14.00%		14.00%
Residential Mortgage | Risk Level, High
Accounts, Notes, Loans and Financing Receivable [Line Items]
Concentration of credit risk, maximum exposure	14,300		14,700
Commitments to Extend Credit
Accounts, Notes, Loans and Financing Receivable [Line Items]
Concentration of credit risk, maximum exposure	12,500		12,700
Loan Origination Commitments
Accounts, Notes, Loans and Financing Receivable [Line Items]
Concentration of credit risk, maximum exposure	9,000		7,800
Interest Only Loans | Risk Level, High
Accounts, Notes, Loans and Financing Receivable [Line Items]
Concentration of credit risk, maximum exposure	9,000		9,400
Interest only period	10		10
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	1,800		1,900
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	$ 5,300		$ 5,278