Reclassifications out of Accumulated Other Comprehensive Loss - Changes in Accumulated Other Comprehensive Loss (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	$ 1,038.0
Other comprehensive income before reclassifications	4.7	$ (3.8)
Amounts reclassified from AOCL	(0.3)	0.2
Total other comprehensive income/(loss)	4.4	(3.6)
Ending Balance	1,078.2
Accumulated Other Comprehensive Loss [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(145.2)	(46.9)
Ending Balance	(140.8)	(50.5)
Defined Benefit Pension Plan Items [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(58.4)	10.7
Other comprehensive income before reclassifications	0.0	0.0
Amounts reclassified from AOCL	(0.3)	0.2
Total other comprehensive income/(loss)	(0.3)	0.2
Ending Balance	(58.7)	10.9
Foreign Currency Translation Items [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(86.8)	(57.6)
Other comprehensive income before reclassifications	4.7	(3.8)
Amounts reclassified from AOCL	0.0	0.0
Total other comprehensive income/(loss)	4.7	(3.8)
Ending Balance	$ (82.1)	$ (61.4)