Accumulated Other Comprehensive Loss - Changes in Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning equity	$ 1,647.9	$ 1,603.2
Other comprehensive income (loss) before reclassifications	9.9
Amounts reclassified from accumulated other comprehensive loss	2.2
Current period other comprehensive income (loss)	12.1
Ending equity	1,678.5	$ 1,588.8
Cash flow hedge (loss) gain
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning equity	(0.8)
Other comprehensive income (loss) before reclassifications	0.4
Amounts reclassified from accumulated other comprehensive loss	0.2
Current period other comprehensive income (loss)	0.6
Ending equity	(0.2)
Unrealized gain (loss) on available-for- sale securities
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning equity	(0.6)
Other comprehensive income (loss) before reclassifications	(0.3)
Amounts reclassified from accumulated other comprehensive loss	0.0
Current period other comprehensive income (loss)	(0.3)
Ending equity	(0.9)
Pension and post retirement benefit plan adjustment
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning equity	(176.5)
Other comprehensive income (loss) before reclassifications	0.0
Amounts reclassified from accumulated other comprehensive loss	2.0
Current period other comprehensive income (loss)	2.0
Ending equity	(174.5)
Cumulative translation adjustment
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning equity	(91.9)
Other comprehensive income (loss) before reclassifications	9.8
Amounts reclassified from accumulated other comprehensive loss	0.0
Current period other comprehensive income (loss)	9.8
Ending equity	(82.1)
AOCI Including Portion Attributable to Noncontrolling Interest
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning equity	(269.8)
Ending equity	$ (257.7)