Supplemental Balance Sheet Data - AOCI (Details) - USD ($) $ in Millions	3 Months Ended						9 Months Ended
	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Sep. 30, 2019	Sep. 30, 2018
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at the beginning of the period	$ 406.5	$ 394.2	$ 390.2	$ 392.5	$ 412.2	$ 399.9	$ 390.2	$ 399.9
Other comprehensive income (loss) before reclassifications							(3.6)
Amounts reclassified from AOCI							4.4
Income (loss) from other comprehensive income items	(5.5)			0.8			0.8	0.8
Provision (benefit) for income taxes	0.3			0.4			2.1	1.5
Other comprehensive income (loss)	(5.8)	6.2	(1.7)	0.4	(8.4)	7.3	(1.3)	(0.7)
Balance at the end of the period	405.5	406.5	394.2	399.1	392.5	412.2	405.5	399.1
Decrease in employee benefit obligation							4.9
Settlement loss							0.1
Income tax benefit	(1.8)			(0.4)			(7.4)	(2.2)
Accumulated Other Comprehensive Loss
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Amounts reclassified from AOCI							4.4	4.5
Income tax benefit							1.1	1.1
Net Unrealized Foreign Currency Translation Loss
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at the beginning of the period			(15.5)				(15.5)
Other comprehensive income (loss) before reclassifications							(8.6)
Amounts reclassified from AOCI							0.0
Income (loss) from other comprehensive income items							(8.6)
Provision (benefit) for income taxes							(0.2)
Other comprehensive income (loss)							(8.4)
Balance at the end of the period	(23.9)						(23.9)
Net Loss from Pension and Other Postretirement Liabilities
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at the beginning of the period			(89.6)				(89.6)
Other comprehensive income (loss) before reclassifications							5.0
Amounts reclassified from AOCI							4.4
Income (loss) from other comprehensive income items							9.4
Provision (benefit) for income taxes							2.3
Other comprehensive income (loss)							7.1
Balance at the end of the period	(82.5)						(82.5)
Accumulated Other Comprehensive Loss
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at the beginning of the period	(100.6)	(106.8)	(105.1)	(94.9)	(86.5)	(94.1)	(105.1)	(94.1)
Other comprehensive income (loss)	(5.8)	6.2	(1.7)	0.4	(8.4)	7.3
Balance at the end of the period	$ (106.4)	$ (100.6)	$ (106.8)	$ (94.5)	$ (94.9)	$ (86.5)	$ (106.4)	$ (94.5)