Other Comprehensive Income (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Beginning Balance	$ (122.1)	$ (137.2)
Other comprehensive income (loss) before reclassifications	2.7	3.1
Income taxes	0.0	(0.2)
Net other comprehensive income (loss) before reclassifications	2.7	2.9
Amounts reclassified from accumulated other comprehensive income (loss)	1.6	1.7
Income taxes	(0.4)	(0.6)
Net amounts reclassified from cumulative other comprehensive income (loss)	1.2	1.1
Total other comprehensive income (loss)	3.9	4.0
Ending Balance	(134.9)	(133.2)
Foreign currency translation adjustments
Beginning Balance	(39.7)	(46.3)
Other comprehensive income (loss) before reclassifications	2.3	2.8
Income taxes	0.0	0.0
Net other comprehensive income (loss) before reclassifications	2.3	2.8
Amounts reclassified from accumulated other comprehensive income (loss)	0.0	0.0
Income taxes	0.0	0.0
Net amounts reclassified from cumulative other comprehensive income (loss)	0.0	0.0
Total other comprehensive income (loss)	2.3	2.8
Ending Balance	(37.4)	(43.5)
Actuarial loss, net of tax
Beginning Balance	(79.5)	(87.7)
Other comprehensive income (loss) before reclassifications		(0.2)
Change benefit obligations, translation adjustment	0.2	(0.2)
Income taxes	0.0	0.0
Net other comprehensive income (loss) before reclassifications	0.2	(0.2)
Amounts reclassified from accumulated other comprehensive income (loss)	1.5	1.4
Income taxes	(0.4)	(0.5)
Net amounts reclassified from cumulative other comprehensive income (loss)	1.1	0.9
Total other comprehensive income (loss)	1.3	0.7
Ending Balance	(95.6)	(87.0)
Prior service cost, net of tax
Beginning Balance	(4.9)	(5.2)
Other comprehensive income (loss) before reclassifications	0.0	0.0
Income taxes	0.0	0.0
Net other comprehensive income (loss) before reclassifications	0.0	0.0
Amounts reclassified from accumulated other comprehensive income (loss)	0.1	0.3
Income taxes	0.0	(0.1)
Net amounts reclassified from cumulative other comprehensive income (loss)	0.1	0.2
Total other comprehensive income (loss)	0.1	0.2
Ending Balance	(4.8)	(5.0)
Unrealized gain (loss) on investments
Beginning Balance	3.5	2.7
Other comprehensive income (loss) before reclassifications	0.2	0.5
Income taxes		(0.2)
Net other comprehensive income (loss) before reclassifications	0.2	0.3
Amounts reclassified from accumulated other comprehensive income (loss)	0.0	0.0
Income taxes	0.0	0.0
Net amounts reclassified from cumulative other comprehensive income (loss)	0.0	0.0
Total other comprehensive income (loss)	0.2	0.3
Ending Balance	4.4	3.0
Other
Beginning Balance	(1.5)	(0.7)
Other comprehensive income (loss) before reclassifications		0.0
Income taxes	0.0	0.0
Net other comprehensive income (loss) before reclassifications	0.0	0.0
Amounts reclassified from accumulated other comprehensive income (loss)	0.0	0.0
Income taxes	0.0	0.0
Net amounts reclassified from cumulative other comprehensive income (loss)	0.0	0.0
Total other comprehensive income (loss)	0.0	0.0
Ending Balance	(1.5)	$ (0.7)
AOCI Attributable to Parent [Member]
Beginning Balance	(122.1)
Ending Balance	(134.9)
Accounting Standards Update 2018-02 [Member]
Effect of adoption of ASU 2018-02	0.0
Ending Balance	(16.7)
Accounting Standards Update 2018-02 [Member] | Foreign currency translation adjustments
Effect of adoption of ASU 2018-02	0.0
Accounting Standards Update 2018-02 [Member] | Actuarial loss, net of tax
Effect of adoption of ASU 2018-02	(17.4)
Accounting Standards Update 2018-02 [Member] | Prior service cost, net of tax
Effect of adoption of ASU 2018-02	0.0
Accounting Standards Update 2018-02 [Member] | Unrealized gain (loss) on investments
Effect of adoption of ASU 2018-02	0.7
Accounting Standards Update 2018-02 [Member] | Other
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)