Loans - High LTV Interest-only and Arm Loans (Parenthetical) (Detail) (USD $) In Millions, unless otherwise specified	6 Months Ended
	Jun. 30, 2013		Dec. 31, 2012
Loans [Line Items]
Residential mortgage loans with high LTV and no mortgage insurance	$ 800	[1]	$ 900	[1]
Sub-prime residential mortgage [Member]
Loans [Line Items]
Residential mortgage loans with high LTV and no mortgage insurance	17		20
Sub-prime residential mortgage loans held for sale excluded from Arm Loan	19		19
Amount of ARM loans to experience first interest rate reset in 2013	140
Amount of ARM loans to experience first interest rate reset in 2014	$ 304

[1] Residential mortgage loans with high LTV and no mortgage insurance includes both fixed rate and adjustable rate mortgages. Excludes $17 million and $20 million of subprime residential mortgage loans held for sale at June 30, 2013 and December 31, 2012, respectively.