Reclassifications out of Accumulated Other Comprehensive Loss - Changes in Accumulated Other Comprehensive Loss (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	$ 918.5
Other comprehensive income before reclassifications	(7.9)
Amounts reclassified from AOCL	(0.0)
Total other comprehensive loss	(7.9)	$ (5.7)
Ending Balance	943.8
Accumulated Other Comprehensive Loss [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(74.4)
Ending Balance	(82.3)
Defined Benefit Pension Plan Items [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(9.3)
Other comprehensive income before reclassifications	0.0
Amounts reclassified from AOCL	(0.0)
Total other comprehensive loss	0.0
Ending Balance	(9.3)
Foreign Currency Translation Items [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(65.1)
Other comprehensive income before reclassifications	(7.9)
Amounts reclassified from AOCL	(0.0)
Total other comprehensive loss	(7.9)
Ending Balance	$ (73.0)