Other Comprehensive (Loss) Income - Schedule of Changes in Accumulated Other Comprehensive Loss (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning Balance	$ (92.2)
Amounts reclassified from accumulated other comprehensive loss	29.3	$ (1.8)
Other comprehensive (loss) income	(22.6)	17.3
Ending Balance	(174.1)
Changes in the Fair Value of Available-for-Sale Securities
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning Balance	119.3
Other comprehensive (loss) income before reclassifications	(60.9)
Amounts reclassified from accumulated other comprehensive loss	28.6
Other comprehensive (loss) income	(32.3)
Ending Balance	87.0
Pension and Other Postretirement Benefits Plan Cost
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning Balance	(159.5)	(727.5)
Other comprehensive (loss) income before reclassifications	0.0	0.0
Amounts reclassified from accumulated other comprehensive loss	0.7	(1.8)
Amounts reclassified due to disposition of a business		1.2
Other comprehensive (loss) income	0.7	(0.6)
Ending Balance	(158.8)	(728.1)
Translation Adjustments
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning Balance	(15.5)	(65.7)
Other comprehensive (loss) income before reclassifications	8.8	18.8
Amounts reclassified from accumulated other comprehensive loss	0.0	0.0
Amounts reclassified due to disposition of a business		(1.1)
Other comprehensive (loss) income	8.8	17.7
Ending Balance	(6.7)	(48.0)
AOCI Attributable to Parent
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning Balance	(55.7)	(793.2)
Other comprehensive (loss) income before reclassifications	(52.1)	18.8
Amounts reclassified from accumulated other comprehensive loss	29.3	(1.8)
Amounts reclassified due to disposition of a business		0.1
Other comprehensive (loss) income	(22.8)	17.1
Ending Balance	$ (78.5)	$ (776.1)