Components of Accumulated Other Comprehensive Income (Loss) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	$ (319.7)	$ (244.3)	$ (283.0)
Net Change	(53.0)	(75.4)	38.7
Ending Balance	(372.7)	(319.7)	(244.3)
Net Unrealized Gains (Losses) on Securities Available for Sale
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	27.6	6.0	101.0
Net Change	(58.6)	21.6	(95.0)
Ending Balance	(31.0)	27.6	6.0
Net Unrealized (Losses) Gains on Cash Flow Hedges
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	(4.7)	2.9	(1.4)
Net Change	1.7	(7.6)	4.3
Ending Balance	(3.0)	(4.7)	2.9
Net Foreign Currency Adjustments
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	(1.7)	7.1	10.5
Net Change	(15.9)	(8.8)	(3.4)
Ending Balance	(17.6)	(1.7)	7.1
Net Pension and Other Postretirement Benefit Adjustments
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	(340.9)	(260.3)	(393.1)
Net Change	19.8	(80.6)	132.8
Ending Balance	$ (321.1)	$ (340.9)	$ (260.3)