MSR (Fair Value of the Servicing Rights) (Detail) - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016	Mar. 31, 2016
Servicing Assets at Fair Value
Fair value at beginning of period	$ 744
Fair value at end of period	776	$ 744
Fixed Rate Residential Mortgage Loans
Servicing Assets at Fair Value
Fair value at beginning of period	722	660	$ 757
Fair value at end of period	756	722	660
Adjustable Rate Residential Mortgage Loans
Servicing Assets at Fair Value
Fair value at beginning of period	22	25	27
Fair value at end of period	20	22	25
Fixed Rate Automobile Loans
Servicing Assets at Fair Value
Fair value at beginning of period	0	0	1
Fair value at end of period	$ 0	$ 0	$ 0