Intangible Assets (Detail) - USD ($) $ in Millions	Mar. 31, 2016	Dec. 31, 2015
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 66	$ 67
Accumulated Amortization	(55)	(55)
Net Carrying Amount	11	12
Core Deposits
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	34	34
Accumulated Amortization	(26)	(26)
Net Carrying Amount	8	8
Other Intangible Assets
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	32	33
Accumulated Amortization	(29)	(29)
Net Carrying Amount	$ 3	$ 4