Other Comprehensive Income (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Beginning Balance	$ (137.2)	$ (146.1)
Other comprehensive income (loss) before reclassifications	3.1	5.3
Income taxes	(0.2)	0.0
Net other comprehensive income (loss) before reclassifications	2.9	5.3
Amounts reclassified from accumulated other comprehensive income (loss)	1.7	1.5
Income taxes	(0.6)	(0.6)
Net amounts reclassified from cumulative other comprehensive income (loss)	1.1	0.9
Total other comprehensive income (loss)	4.0	6.2
Ending Balance	(133.2)	(139.9)
Foreign currency translation adjustments
Beginning Balance	(46.3)	(55.1)
Other comprehensive income (loss) before reclassifications	2.8	6.1
Income taxes	0.0	0.0
Net other comprehensive income (loss) before reclassifications	2.8	6.1
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)	2.8	6.1
Ending Balance	(43.5)	(49.0)
Actuarial loss, net of tax
Beginning Balance	(87.7)	(87.8)
Other comprehensive income (loss) before reclassifications	(0.2)	(0.8)
Income taxes	0.0	0.0
Net other comprehensive income (loss) before reclassifications	(0.2)	(0.8)
Amounts reclassified from accumulated other comprehensive income (loss)	1.4	1.4
Income taxes	(0.5)	(0.6)
Net amounts reclassified from cumulative other comprehensive income (loss)	0.9	0.8
Total other comprehensive income (loss)	0.7	0.0
Ending Balance	(87.0)	(87.8)
Prior service cost, net of tax
Beginning Balance	(5.2)	(5.5)
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)	0.3	0.1
Income taxes	(0.1)	0.0
Net amounts reclassified from cumulative other comprehensive income (loss)	0.2	0.1
Total other comprehensive income (loss)	0.2	0.1
Ending Balance	(5.0)	(5.4)
Unrealized gain (loss) on investments
Beginning Balance	2.7	3.3
Other comprehensive income (loss) before reclassifications	0.5	0.0
Income taxes	(0.2)	0.0
Net other comprehensive income (loss) before reclassifications	0.3	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)	0.3	0.0
Ending Balance	3.0	3.3
Other
Beginning Balance	(0.7)	(1.0)
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)	0.0	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	$ (0.7)	$ (1.0)