Intangible Assets - Schedule of Intangible Assets (Detail) (USD $) In Millions, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Finite-Lived Intangible Assets [Line Items]
Total intangible assets	$ 295	$ 247
Mortgage servicing rights [Member]
Finite-Lived Intangible Assets [Line Items]
Total intangible assets	235	179
Mortage Servicing Rights - Residential Real Estate [Member]
Finite-Lived Intangible Assets [Line Items]
Total intangible assets	224	168
Mortgage Servicing Rights - Commercial Real Estate [Member]
Finite-Lived Intangible Assets [Line Items]
Total intangible assets	11	11
Purchased credit card relationships
Finite-Lived Intangible Assets [Line Items]
Total intangible assets	55	60
Favorable lease argeement
Finite-Lived Intangible Assets [Line Items]
Total intangible assets	$ 5	$ 8