Accumulated Other Comprehensive Income (Loss) - Reclasses Out Of AOCI (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Other Comprehensive Income (Loss), Net of Tax [Abstract]
Beginning balance			$ 337.1
Other comprehensive income	$ 21.7	$ 5.0	68.2	$ 34.2
Ending balance	458.4		458.4
Benefit Plan Adjustments
Other Comprehensive Income (Loss), Net of Tax [Abstract]
Beginning balance			(559.6)
Other comprehensive income (loss) before reclassifications			(7.8)
Amounts reclassified from accumulated other comprehensive loss			25.9
Other comprehensive income	5.2	7.8	18.1	22.6
Ending balance	(541.5)		(541.5)
Foreign Currency Translation Adjustments
Other Comprehensive Income (Loss), Net of Tax [Abstract]
Beginning balance			(349.1)
Other comprehensive income (loss) before reclassifications			48.5
Amounts reclassified from accumulated other comprehensive loss			0.0
Other comprehensive income	14.6	(3.4)	48.5	10.2
Ending balance	(300.6)		(300.6)
Unrealized Gains (Losses) on Available-for-Sale Securities
Other Comprehensive Income (Loss), Net of Tax [Abstract]
Beginning balance			1.0
Other comprehensive income (loss) before reclassifications			0.9
Amounts reclassified from accumulated other comprehensive loss			(0.6)
Other comprehensive income	(0.2)		0.3	0.0
Ending balance	1.3		1.3
Gains (Losses) on Cash Flow Hedges
Other Comprehensive Income (Loss), Net of Tax [Abstract]
Beginning balance			0.7
Other comprehensive income (loss) before reclassifications			(0.3)
Amounts reclassified from accumulated other comprehensive loss			0.2
Other comprehensive income	0.0	0.1	(0.1)	(0.1)
Ending balance	0.6		0.6
Accumulated Other Comprehensive Loss
Other Comprehensive Income (Loss), Net of Tax [Abstract]
Beginning balance			(907.0)
Other comprehensive income (loss) before reclassifications			41.3
Amounts reclassified from accumulated other comprehensive loss			25.5
Other comprehensive income	19.6	$ 4.5	66.8	$ 32.7
Ending balance	$ (840.2)		$ (840.2)