Other Comprehensive Income (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Beginning Balance	$ (146.4)	$ (122.1)
Effect of adoption of ASU 2018-02		(16.7)
Other comprehensive income (loss) before reclassifications	1.0	2.7
Other Comprehensive Income (Loss) before Reclassifications, Tax	0.1	0.0
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	1.1	2.7
Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax	1.0	1.6
Reclassification from AOCI, Current Period, Tax	0.0	(0.4)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	0.9	1.2
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	2.0	3.9
Ending Balance	(144.4)	(134.9)
Foreign currency translation adjustments
Beginning Balance	(57.0)	(39.7)
Other comprehensive income (loss) before reclassifications	1.6	2.3
Other Comprehensive Income (Loss) before Reclassifications, Tax	0.0	0.0
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	1.6	2.3
Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax	0.0	0.0
Reclassification from AOCI, Current Period, Tax	0.0	0.0
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	0.0	0.0
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	1.6	2.3
Ending Balance	(55.4)	(37.4)
Actuarial loss, net of tax
Beginning Balance	(88.2)	(79.5)
Effect of adoption of ASU 2018-02		(17.4)
Other comprehensive income (loss) before reclassifications	(0.1)	0.2
Other Comprehensive Income (Loss) before Reclassifications, Tax	0.0	0.0
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	(0.1)	0.2
Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax	1.2	1.5
Reclassification from AOCI, Current Period, Tax	(0.3)	(0.4)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	0.9	1.1
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	0.8	1.3
Ending Balance	(87.4)	(95.6)
Prior service cost, net of tax
Beginning Balance	(4.5)	(4.9)
Other comprehensive income (loss) before reclassifications	0.0	0.0
Other Comprehensive Income (Loss) before Reclassifications, Tax	0.0	0.0
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	0.0	0.0
Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax	0.0	0.1
Reclassification from AOCI, Current Period, Tax	0.0	0.0
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	0.0	0.1
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	0.0	0.1
Ending Balance	(4.5)	(4.8)
Unrealized gain (loss) on investments
Beginning Balance	4.3	3.5
Other comprehensive income (loss) before reclassifications	(0.5)	0.2
Other Comprehensive Income (Loss) before Reclassifications, Tax	0.1	0.0
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	(0.4)	0.2
Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax	0.0	0.0
Reclassification from AOCI, Current Period, Tax	0.0	0.0
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	0.0	0.0
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	(0.4)	0.2
Ending Balance	3.9	4.4
Other
Beginning Balance	(1.0)	(1.5)
Other comprehensive income (loss) before reclassifications	0.0	0.0
Other Comprehensive Income (Loss) before Reclassifications, Tax	0.0	0.0
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	0.0	0.0
Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax	0.0	0.0
Reclassification from AOCI, Current Period, Tax	0.0	0.0
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	0.0	0.0
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	0.0	0.0
Ending Balance	(1.0)	(1.5)
AOCI Attributable to Parent [Member]
Beginning Balance	(146.4)	(122.1)
Ending Balance	$ (144.4)	(134.9)
Accounting Standards Update 2018-02 [Member]
Effect of adoption of ASU 2018-02		0.0
Accounting Standards Update 2018-02 [Member] | AOCI Attributable to Parent [Member]
Effect of adoption of ASU 2018-02		$ (16.7)