MSR (Fair Value of the Servicing Rights) (Detail) - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016	Sep. 30, 2016
Servicing Assets at Fair Value
Fair value at beginning of period	$ 744
Fair value at end of period	848	$ 744
Fixed Rate Residential Mortgage Loans
Servicing Assets at Fair Value
Fair value at beginning of period	722	597	$ 757
Fair value at end of period	831	722	597
Adjustable Rate Residential Mortgage Loans
Servicing Assets at Fair Value
Fair value at beginning of period	22	22	27
Fair value at end of period	17	22	22
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