Loans - Additional Information (Detail) (USD $)	3 Months Ended				9 Months Ended
	Sep. 30, 2012		Sep. 30, 2011		Sep. 30, 2012		Sep. 30, 2011		Dec. 31, 2011
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans transferred from loans held for sale to loans	$ 3,000,000		$ 7,000,000		$ 34,000,000		$ 53,000,000
Value of loans transferred from LHFI to LHFS	2,000,000,000		459,000,000		3,112,000,000		657,000,000
Loans held for investment sold	649,000,000		202,000,000		2,000,000,000		479,000,000
Gain on sale of loans held for investment	9,000,000		10,000,000		62,000,000		20,000,000
PrincipalForgivenessRestructuringImpact	1,000,000		3,000,000		2,000,000		12,000,000
Loans and Leases Receivable, Impaired, Commitment to Lend	3,000,000				3,000,000				5,000,000
Financing Receivable, Amount Restructured During Period, Principal Forgiveness Granted	10,000,000	[1],[2]	11,000,000	[1],[3]	24,000,000	[1],[2]	87,000,000	[1],[3]
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
Guaranteed Student Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Student loan portfolio percentage current	86.00%				86.00%				79.00%
Accrual Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accruing TDRs included in impaired loan balances	2,600,000,000				2,600,000,000				2,600,000,000
Accruing TDRs current	95.00%				95.00%				93.00%
Cross-Border Outstanding Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Concentration of credit risk, maximum exposure	647,000,000				647,000,000				630,000,000
Residential Mortgage | Risk Level, High
Accounts, Notes, Loans and Financing Receivable [Line Items]
Concentration of credit risk, maximum exposure	13,700,000,000				13,700,000,000				14,700,000,000
Residential Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Concentration of credit risk, maximum exposure	44,600,000,000				44,600,000,000				46,700,000,000
Maximum Exposure to Loss, Percent	37.00%				37.00%				38.00%
Government guaranteed percent	11.00%				11.00%				14.00%
Commitments to Extend Credit
Accounts, Notes, Loans and Financing Receivable [Line Items]
Concentration of credit risk, maximum exposure	12,000,000,000				12,000,000,000				12,700,000,000
Loan Origination Commitments
Accounts, Notes, Loans and Financing Receivable [Line Items]
Concentration of credit risk, maximum exposure	9,600,000,000				9,600,000,000				7,800,000,000
Interest Only Loans | Risk Level, High
Accounts, Notes, Loans and Financing Receivable [Line Items]
Concentration of credit risk, maximum exposure	8,100,000,000				8,100,000,000				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	1,600,000,000				1,600,000,000				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				$ 5,700,000,000				$ 5,300,000,000

[1] Includes loans modified under the terms of a TDR that were charged-off during the period.

[2] Restructured loans which had forgiveness of amounts contractually due under the terms of the loan typically have had multiple concessions including rate modifications and/or term extensions. The total amount of charge-offs associated with principal forgiveness was during the three and nine months ended September 30, 2012 was $1 million and $2 million, respectively.

[3] Restructured loans which had forgiveness of amounts contractually due under the terms of the loan typically have had multiple concessions including rate modifications and/or term extensions. The total amount of charge-offs associated with principal forgiveness during the three and nine months ended September 30, 2011 was $3 million and $12 million, respectively.