Components of Accumulated Other Comprehensive Income (Loss) (AOCI) (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Accumulated Other Comprehensive Income (Loss) [Line Items]
Ending Balance	$ (273.7)	$ (205.2)	$ (273.7)	$ (205.2)
Net Change	(7.3)	30.9	46.0	39.1
Beginning Balance			(319.7)	(244.3)
Net Unrealized Gains (Losses) on Securities Available for Sale
Accumulated Other Comprehensive Income (Loss) [Line Items]
Ending Balance	59.3	44.0	59.3	44.0
Net Change			31.7	38.0
Beginning Balance			27.6	6.0
Net Unrealized Gains (Losses) on Cash Flow Hedges Designations
Accumulated Other Comprehensive Income (Loss) [Line Items]
Ending Balance	(2.6)	3.9	(2.6)	3.9
Net Change			2.1	1.0
Beginning Balance			(4.7)	2.9
Net Foreign Currency Adjustments
Accumulated Other Comprehensive Income (Loss) [Line Items]
Ending Balance	(1.8)	0.2	(1.8)	0.2
Net Change			(0.1)	(6.9)
Beginning Balance			(1.7)	7.1
Net Pension and Other Postretirement Benefit Adjustments
Accumulated Other Comprehensive Income (Loss) [Line Items]
Ending Balance	$ (328.6)	$ (253.3)	(328.6)	(253.3)
Net Change			12.3	7.0
Beginning Balance			$ (340.9)	$ (260.3)