Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Accumulated balances for each classification of comprehensive income (loss)
Balance at the beginning of the period	$ 2,466.9	$ 2,347.4
Other comprehensive income	11.7	10.4
Balance at the end of the period	2,518.2	2,387.5
Accrued post-retirement benefit liability
Accumulated balances for each classification of comprehensive income (loss)
Balance at the beginning of the period	(26.4)	(27.4)
Other comprehensive income before reclassifications	0.0	0.0
Amounts reclassified from accumulated other comprehensive loss	0.6	0.6
Income tax (expense) benefit	(0.2)	(0.2)
Other comprehensive income	0.4	0.4
Balance at the end of the period	(26.0)	(27.0)
Foreign currency translation
Accumulated balances for each classification of comprehensive income (loss)
Balance at the beginning of the period	(96.7)	(60.0)
Other comprehensive income before reclassifications	11.4	10.2
Amounts reclassified from accumulated other comprehensive loss	0.0	0.0
Income tax (expense) benefit	0.0	0.0
Other comprehensive income	11.4	10.2
Balance at the end of the period	(85.3)	(49.8)
Other
Accumulated balances for each classification of comprehensive income (loss)
Balance at the beginning of the period	0.9	0.3
Other comprehensive income before reclassifications	0.1	0.0
Amounts reclassified from accumulated other comprehensive loss	(0.2)	(0.3)
Income tax (expense) benefit	0.0	0.1
Other comprehensive income	(0.1)	(0.2)
Balance at the end of the period	0.8	0.1
Accumulated Other Comprehensive Income (loss).
Accumulated balances for each classification of comprehensive income (loss)
Balance at the beginning of the period	(122.2)	(87.1)
Other comprehensive income before reclassifications	11.5	10.2
Amounts reclassified from accumulated other comprehensive loss	0.4	0.3
Income tax (expense) benefit	(0.2)	(0.1)
Other comprehensive income	11.7	10.4
Balance at the end of the period	$ (110.5)	$ (76.7)