Intangible Assets (Intangible Assets) (Detail) - USD ($) $ in Millions	Sep. 30, 2016	Dec. 31, 2015
Finite-Lived Intangible Assets
Gross Carrying Amount	$ 49	$ 67
Accumulated Amortization	(39)	(55)
Net Carrying Amount	10	12
Core Deposits
Finite-Lived Intangible Assets
Gross Carrying Amount	34	34
Accumulated Amortization	(26)	(26)
Net Carrying Amount	8	8
Other Intangible Assets
Finite-Lived Intangible Assets
Gross Carrying Amount	15	33
Accumulated Amortization	(13)	(29)
Net Carrying Amount	$ 2	$ 4