Fair Value of the Servicing Assets (Detail) (USD $) In Millions, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012	Jun. 30, 2012	Dec. 31, 2011
Fixed Rate Residential Mortgage
Servicing Assets at Fair Value
Fair value at beginning of period	$ 855	$ 664	$ 702	$ 649
Fair value at end of period	855	664	702	649
Adjustable Rate Residential Mortgage
Servicing Assets at Fair Value
Fair value at beginning of period	39	33	34	32
Fair value at end of period	39	33	34	32
Fixed Rate Automobile Loans
Servicing Assets at Fair Value
Fair value at beginning of period	5
Fair value at end of period	$ 5