Accumulated Other Comprehensive (Loss) Income (Components of accumulated comprehensive loss) (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Increase (Decrease) in Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	$ 359,100,000	$ 331,600,000	$ 357,900,000	$ 349,600,000
Currency translation	1,600,000	2,900,000	(2,700,000)	(13,700,000)
Pension and other postretirement benefits	200,000	400,000	400,000	900,000
Ending balance	353,200,000	316,200,000	353,200,000	316,200,000
Income taxes provided on currency translation as foreign earnings permanently reinvested	0	0	0	0
Cumulative Translation Adjustment
Increase (Decrease) in Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	(12,600,000)	(39,000,000.0)	(8,300,000)	(22,400,000)
Ending balance	(11,000,000.0)	(36,100,000)	(11,000,000.0)	(36,100,000)
Pension and Postretirement Benefits
Increase (Decrease) in Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	(9,600,000)	(14,100,000)	(9,800,000)	(14,600,000)
Ending balance	(9,400,000)	(13,700,000)	(9,400,000)	(13,700,000)
Accumulated Other Comprehensive (Loss) Income
Increase (Decrease) in Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	(22,200,000)	(53,100,000)	(18,100,000)	(37,000,000.0)
Ending balance	$ (20,400,000)	$ (49,800,000)	$ (20,400,000)	$ (49,800,000)