Loans - First and Second Liens within Outstanding Residential Mortgage Loan Portfolio (Detail) (USD $) In Millions, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012	Jun. 30, 2012
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	$ 66,705	$ 63,258	$ 56,064
Consumer Loans [Member] | Residential Mortgage [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	18,009	17,695
Consumer Loans [Member] | Residential Mortgage [Member] | First lien of Closed end [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	15,837	15,371
Consumer Loans [Member] | Residential Mortgage [Member] | Second lien of Closed end [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	159	186
Consumer Loans [Member] | Residential Mortgage [Member] | Revolving Second lien [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	$ 2,013	$ 2,138