Accumulated Other Comprehensive (Loss) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at the beginning of the period	$ (122.2)	$ (87.1)
Other comprehensive (loss) income before reclassifications	31.0	(36.7)
Amounts reclassified from accumulated other comprehensive loss	2.0	2.2
Income tax (expense) benefit	3.5	(0.6)
Other comprehensive income (loss)	36.5	(35.1)	$ (25.3)
Balance at the end of the period	(85.7)	(122.2)	(87.1)
Accrued post-retirement benefit liability
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at the beginning of the period	(26.4)	(27.4)
Other comprehensive (loss) income before reclassifications	(11.2)	(0.6)
Amounts reclassified from accumulated other comprehensive loss	2.5	2.3
Income tax (expense) benefit	3.5	(0.7)
Other comprehensive income (loss)	(5.2)	1.0
Balance at the end of the period	(31.6)	(26.4)	(27.4)
Foreign currency translation
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at the beginning of the period	(96.7)	(60.0)
Other comprehensive (loss) income before reclassifications	46.6	(36.7)
Other comprehensive income (loss)	46.6	(36.7)
Balance at the end of the period	(50.1)	(96.7)	(60.0)
Other
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at the beginning of the period	0.9	0.3
Other comprehensive (loss) income before reclassifications	(4.4)	0.6
Amounts reclassified from accumulated other comprehensive loss	(0.5)	(0.1)
Income tax (expense) benefit	0.0	0.1
Other comprehensive income (loss)	(4.9)	0.6
Balance at the end of the period	(4.0)	0.9	0.3
Accumulated Other Comprehensive Income (loss).
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Other comprehensive income (loss)	$ 36.5	$ (35.1)	$ (25.3)