Income Taxes - Components of Comprehensive Provision for Income Taxes Allocation (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Schedule Of Income Tax [Line Items]
Net income (loss)	$ 12.3	$ (13.6)	$ 27.0	$ (51.3)
Other comprehensive income (loss):
Marketable securities		3.8	(6.7)	4.5
Currency translation	(8.9)	4.1	(10.5)	2.8
Total	4.2	(4.6)	12.3	(40.8)
Defined Benefit Pension Plans
Other comprehensive income (loss):
Benefit plans	0.8	1.1	2.6	3.3
OPEB
Other comprehensive income (loss):
Benefit plans			$ (0.1)	$ (0.1)