Intangible Assets (Detail) - USD ($) $ in Millions	Sep. 30, 2015	Dec. 31, 2014
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 67	$ 167
Accumulated Amortization	(54)	(152)
Net Carrying Amount	13	15
Core Deposits
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	34	122
Accumulated Amortization	(25)	(112)
Net Carrying Amount	9	10
Other Intangible Assets
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	33	45
Accumulated Amortization	(29)	(40)
Net Carrying Amount	$ 4	$ 5