Intangible Assets - Schedule of Intangible Assets (Detail) - USD ($) $ in Millions	Sep. 30, 2015	Dec. 31, 2014
Finite-Lived Intangible Assets [Line Items]
Total intangible assets	$ 172	$ 206
Purchased credit card relationships [Member]
Finite-Lived Intangible Assets [Line Items]
Total intangible assets	42	47
Residential Mortgage [Member] | Mortgage servicing rights [Member]
Finite-Lived Intangible Assets [Line Items]
Total intangible assets	$ 130	$ 159