Loans - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Dec. 31, 2012
Accounts, Notes, Loans and Financing Receivable [Line Items]
Net deferred origination costs	$ 64		$ 30
Net unamortized premium on loans	23		25
Amortized net premiums on loans	2	9
Total nonaccruing loans	1,466		1,629
Current Interest Income Of Nonaccrual Loans	31	29
Current Interest Income Expense And Other Income Included In Finance For Loans	5	(2)
Commercial loans removed from TDR classification	11
Commercial loans held for sale	399		1,018
Consumer Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total nonaccruing loans	1,105		1,129
Weighted Average Rate Reduction on TDR Loans	1.99%	1.81%
Commercial loans held for sale	341		537
Residential Mortgage [Member] | Consumer Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total nonaccruing loans	1,026		1,038
Commercial loans held for sale	$ 277		$ 472