Transfers of Financial Assets and Mortgage Servicing Assets (Narrative) (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014	Dec. 31, 2014
Securitization or Asset-backed Financing Arrangement, Financial Asset for which Transfer is Accounted as Sale [Line Items]
Number of days required to repurchase mortgage loans			90 days
Residential Portfolio Segment [Member]
Securitization or Asset-backed Financing Arrangement, Financial Asset for which Transfer is Accounted as Sale [Line Items]
Retained servicing rights					$ 2,400.0
Servicing Asset at Amortized Cost	$ 20.0		$ 20.0		$ 19.4
Bank servicing fees	0.4	$ 0.3		$ 0.8
Residential Mortgage [Member]
Securitization or Asset-backed Financing Arrangement, Financial Asset for which Transfer is Accounted as Sale [Line Items]
Retained servicing rights	$ 2,400.0		$ 2,400.0