Accumulated Other Comprehensive Income (Loss) - Details of Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance			$ 152.3
Other comprehensive income (loss) before reclassifications			(27.9)	$ 107.4
Less: amounts reclassified from accumulated other comprehensive income			2.1	5.8
Other comprehensive (loss) income	$ (11.9)	$ 84.7	(25.8)	113.2
Ending balance	(445.7)		(445.7)
Unrecognized Pension Items
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance			(103.4)	(276.7)
Other comprehensive income (loss) before reclassifications			1.7	175.0
Less: amounts reclassified from accumulated other comprehensive income			1.6	4.9
Other comprehensive (loss) income			3.3	179.9
Ending balance	(100.1)	(96.8)	(100.1)	(96.8)
Cumulative Translation Adjustment
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance			(694.4)	(701.9)
Other comprehensive income (loss) before reclassifications			(40.6)	5.5
Less: amounts reclassified from accumulated other comprehensive income			0.0	0.0
Other comprehensive (loss) income			(40.6)	5.5
Ending balance	(735.0)	(696.4)	(735.0)	(696.4)
Cumulative Translation Adjustment | Intra-entity transactions
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Intra-entity currency translation adjustment in AOCI	63.6	(52.2)	63.6	(52.2)
Unrecognized Gains (Losses) on Derivative Instruments | Net Investment Hedge
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance			(46.8)	21.0
Other comprehensive income (loss) before reclassifications			9.1	(64.0)
Less: amounts reclassified from accumulated other comprehensive income			0.0	0.0
Other comprehensive (loss) income			9.1	(64.0)
Ending balance	(37.7)	(43.0)	(37.7)	(43.0)
Unrecognized Gains (Losses) on Derivative Instruments | Cash Flow Hedge
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance			(0.3)	8.5
Other comprehensive income (loss) before reclassifications			1.9	(9.1)
Less: amounts reclassified from accumulated other comprehensive income			0.5	0.9
Other comprehensive (loss) income			2.4	(8.2)
Ending balance	2.1	0.3	2.1	0.3
Accumulated Other Comprehensive Income (Loss), Net of Taxes
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance			(844.9)	(949.1)
Ending balance	$ (870.7)	$ (835.9)	$ (870.7)	$ (835.9)