Supplemental Balance Sheet Data - AOCI (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at the beginning of the period	$ 390.2	$ 399.9
OCI, before Reclassifications, before Tax, Attributable to Parent	(3.2)
Amounts reclassified from AOCI	1.7
Income (loss) from other comprehensive income items	(1.5)	8.3
Provision (benefit) for income taxes	0.2	1.0
Other comprehensive income (loss)	(1.7)	7.3
Balance at the end of the period	394.2	412.2
Income tax benefit	(2.4)	(4.6)
Accumulated Other Comprehensive Income (Loss)
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Amounts reclassified from AOCI		1.6
Income tax benefit	0.4	0.4
Net Unrealized Foreign Currency Translation Gain (Loss)
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at the beginning of the period	(15.5)
OCI, before Reclassifications, before Tax, Attributable to Parent	(3.2)
Amounts reclassified from AOCI	0.0
Income (loss) from other comprehensive income items	(3.2)
Provision (benefit) for income taxes	(0.2)
Other comprehensive income (loss)	(3.0)
Balance at the end of the period	(18.5)
Net Gain (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)
OCI, before Reclassifications, before Tax, Attributable to Parent	0.0
Amounts reclassified from AOCI	1.7
Income (loss) from other comprehensive income items	1.7
Provision (benefit) for income taxes	0.4
Other comprehensive income (loss)	1.3
Balance at the end of the period	(88.3)
Accumulated Other Comprehensive Income (Loss)
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at the beginning of the period	(105.1)	(94.1)
Other comprehensive income (loss)	(1.7)	7.3
Balance at the end of the period	$ (106.8)	$ (86.5)