Intangible Assets - Schedule of Intangible Assets (Detail) (USD $) In Millions, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Finite-Lived Intangible Assets [Line Items]
Total intangible assets	$ 186	$ 206
Purchased credit card relationships [Member]
Finite-Lived Intangible Assets [Line Items]
Total intangible assets	46	47
Residential Mortgage [Member] | Mortgage servicing rights [Member]
Finite-Lived Intangible Assets [Line Items]
Total intangible assets	$ 140	$ 159