Other Comprehensive (Loss) Income - Schedule of Components of Other Comprehensive (Loss) Income and Income Tax (Benefit) Expense Allocated to Each Component (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Accumulated Other Comprehensive Income Loss [Line Items]
Other comprehensive (loss) income, Before Tax Amount	$ (64.1)	$ (11.6)	$ (89.4)	$ 11.5
Other comprehensive (loss) income, Income Tax Expense	0.3	4.2	(2.4)	10.0
Other comprehensive (loss) income	(64.4)	(15.8)	(87.0)	1.5
Translation adjustments
Accumulated Other Comprehensive Income Loss [Line Items]
Other comprehensive (loss) income, Before Tax Amount	20.1	(22.5)	29.1	(4.6)
Other comprehensive (loss) income, Income Tax Expense	0.0	0.0	0.0	0.0
Other comprehensive (loss) income	20.1	(22.5)	29.1	(4.6)
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	1.0	10.9	2.0	16.1
Other comprehensive (loss) income, Income Tax Expense	0.3	4.2	0.6	10.0
Other comprehensive (loss) income	0.7	$ 6.7	1.4	$ 6.1
Adjustments for available-for-sale securities
Accumulated Other Comprehensive Income Loss [Line Items]
Other comprehensive (loss) income, Before Tax Amount	(85.2)		(120.5)
Other comprehensive (loss) income, Income Tax Expense	0.0		(3.0)
Other comprehensive (loss) income	$ (85.2)		$ (117.5)