Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 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 (loss)	$ 13.6	$ (0.3)	44.9	(4.6)
Balance at the end of the period	2,436.3	2,446.9	2,436.3	2,446.9
Accrued post-retirement benefit liability
Accumulated balances for each classification of comprehensive income (loss)
Balance at the beginning of the period	(25.6)	(26.6)	(26.4)	(27.4)
Other comprehensive income (loss) before reclassifications	0.0	0.0	0.0	0.0
Amounts reclassified from accumulated other comprehensive loss	0.6	0.6	1.9	1.8
Net income tax expense	(0.2)	(0.3)	(0.7)	(0.7)
Other comprehensive income (loss)	0.4	0.3	1.2	1.1
Balance at the end of the period	(25.2)	(26.3)	(25.2)	(26.3)
Foreign currency translation
Accumulated balances for each classification of comprehensive income (loss)
Balance at the beginning of the period	(65.5)	(64.8)	(96.7)	(60.0)
Other comprehensive income (loss) before reclassifications	13.4	(0.5)	44.6	(5.3)
Amounts reclassified from accumulated other comprehensive loss	0.0	0.0	0.0	0.0
Net income tax expense	0.0	0.0	0.0	0.0
Other comprehensive income (loss)	13.4	(0.5)	44.6	(5.3)
Balance at the end of the period	(52.1)	(65.3)	(52.1)	(65.3)
Other, net
Accumulated balances for each classification of comprehensive income (loss)
Balance at the beginning of the period	0.2	0.0	0.9	0.3
Other comprehensive income (loss) before reclassifications	(0.2)	(0.1)	(0.4)	(0.3)
Amounts reclassified from accumulated other comprehensive loss	0.0	0.0	(0.5)	(0.2)
Net income tax expense	0.0	0.0	0.0	0.1
Other comprehensive income (loss)	(0.2)	(0.1)	(0.9)	(0.4)
Balance at the end of the period	0.0	(0.1)	0.0	(0.1)
Accumulated Other Comprehensive Income (loss).
Accumulated balances for each classification of comprehensive income (loss)
Balance at the beginning of the period	(90.9)	(91.4)	(122.2)	(87.1)
Other comprehensive income (loss) before reclassifications	13.2	(0.6)	44.2	(5.6)
Amounts reclassified from accumulated other comprehensive loss	0.6	0.6	1.4	1.6
Net income tax expense	(0.2)	(0.3)	(0.7)	(0.6)
Other comprehensive income (loss)	13.6	(0.3)	44.9	(4.6)
Balance at the end of the period	$ (77.3)	$ (91.7)	$ (77.3)	$ (91.7)