Fair Value of the Servicing Rights (Detail) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Fixed Rate Residential Mortgage Loans
Servicing Rights at Fair Value
Fair value at beginning of period	$ 823	$ 929
Fair value at end of period	757	823
Adjustable Rate Residential Mortgage Loans
Servicing Rights at Fair Value
Fair value at beginning of period	33	38
Fair value at end of period	27	33
Fixed Rate Automobile Loans
Servicing Rights at Fair Value
Fair value at beginning of period	2	4
Fair value at end of period	$ 1	$ 2