Comprehensive Income - Schedule of Components of Other Comprehensive (loss) Income and Income Tax Expense Allocated to Each Component (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Accumulated Other Comprehensive Income Loss [Line Items]
Other comprehensive (loss) income, Before Tax Amount	$ 104.2	$ 4.6	$ (435.9)
Other comprehensive (loss) income, Income Tax Expense	12.0	25.4	(149.9)
Other comprehensive (loss) income, Net of Tax Amount	92.2	(20.8)	(286.0)
Translation adjustments
Accumulated Other Comprehensive Income Loss [Line Items]
Other comprehensive (loss) income, Before Tax Amount	(38.3)	(55.7)	(45.2)
Other comprehensive (loss) income, Income Tax Expense		0.0	0.0
Other comprehensive (loss) income, Net of Tax Amount	(38.3)	(55.7)	(45.2)
Adjustment for net periodic pension and other postretirement benefits plan cost
Accumulated Other Comprehensive Income Loss [Line Items]
Other comprehensive (loss) income, Before Tax Amount	20.2	60.2	(390.9)
Other comprehensive (loss) income, Income Tax Expense	9.0	25.4	(150.0)
Other comprehensive (loss) income, Net of Tax Amount	11.2	34.8	(240.9)
Unrealized gain on available-for-sale securities
Accumulated Other Comprehensive Income Loss [Line Items]
Other comprehensive (loss) income, Before Tax Amount	122.3
Other comprehensive (loss) income, Income Tax Expense	3.0	0.0	0.0
Other comprehensive (loss) income, Net of Tax Amount	$ 119.3
Change in fair value of derivatives
Accumulated Other Comprehensive Income Loss [Line Items]
Other comprehensive (loss) income, Before Tax Amount		0.1	0.2
Other comprehensive (loss) income, Income Tax Expense		0.0	0.1
Other comprehensive (loss) income, Net of Tax Amount		$ 0.1	$ 0.1