Components of Accumulated Other Comprehensive Income (Loss) (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Accumulated Other Comprehensive Income (Loss) [Line Items]
Ending Balance	$ (319.7)	$ (244.3)	$ (283.0)
Net Change	(75.4)	38.7	62.6
Beginning Balance	(244.3)	(283.0)	(345.6)
Net Unrealized Gains (Losses) on Securities Available for Sale
Accumulated Other Comprehensive Income (Loss) [Line Items]
Ending Balance	27.6	6.0	101.0
Net Change	21.6	(95.0)	61.2
Beginning Balance	6.0	101.0	39.8
Net Unrealized (Losses) Gains on Cash Flow Hedges Designations
Accumulated Other Comprehensive Income (Loss) [Line Items]
Ending Balance	(4.7)	2.9	(1.4)
Net Change	(7.6)	4.3	5.6
Beginning Balance	2.9	(1.4)	(7.0)
Net Foreign Currency Adjustments
Accumulated Other Comprehensive Income (Loss) [Line Items]
Ending Balance	(1.7)	7.1	10.5
Net Change	(8.8)	(3.4)	20.0
Beginning Balance	7.1	10.5	(9.5)
Net Pension and Other Postretirement Benefit Adjustments
Accumulated Other Comprehensive Income (Loss) [Line Items]
Ending Balance	(340.9)	(260.3)	(393.1)
Net Change	(80.6)	132.8	(24.2)
Beginning Balance	$ (260.3)	$ (393.1)	$ (368.9)