Significant Accounting Policies Accumulated Other Comprehensive Income (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]
Accumulated other comprehensive income (loss), beginning of period		$ (145.8)
Reclassification from AOCI, Current Period, Tax [Abstract]
Total other comprehensive income (loss), net of income taxes		138.2	$ (131.4)	$ (113.9)
Accumulated other comprehensive income (loss), end of period		(7.6)	(145.8)
Foreign Currency Translation Adjustment [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Accumulated other comprehensive income (loss), beginning of period		(72.6)	51.2	182.9
Other Comprehensive Income (Loss) before Reclassifications Tax [Abstract]
Increase (decrease)		136.6	(123.8)	(131.7)
Income tax impact		0.0	0.0	0.0
Other comprehensive income (loss) before reclassifications, net of income taxes		136.6	(123.8)	(131.7)
Reclassification from AOCI, Current Period, Tax [Abstract]
Increase (decrease)		0.0	0.0	0.0
Income tax impact		0.0	0.0	0.0
Amounts reclassified from accumulated other comprehensive income (loss), net of income taxes		0.0	0.0	0.0
Total other comprehensive income (loss), net of income taxes		136.6	(123.8)	(131.7)
Accumulated other comprehensive income (loss), end of period		64.0	(72.6)	51.2
Pension Adjustments [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Accumulated other comprehensive income (loss), beginning of period	[1]	(73.2)	(65.6)	(83.4)
Other Comprehensive Income (Loss) before Reclassifications Tax [Abstract]
Increase (decrease)	[1]	(3.5)	(13.8)	17.6
Income tax impact	[1]	0.9	2.0	(5.0)
Other comprehensive income (loss) before reclassifications, net of income taxes	[1]	(2.6)	(11.8)	12.6
Reclassification from AOCI, Current Period, Tax [Abstract]
Increase (decrease)	[1],[2]	5.5	5.5	6.9
Income tax impact	[1]	(1.3)	(1.3)	(1.7)
Amounts reclassified from accumulated other comprehensive income (loss), net of income taxes	[1]	4.2	4.2	5.2
Total other comprehensive income (loss), net of income taxes	[1]	1.6	(7.6)	17.8
Accumulated other comprehensive income (loss), end of period	[1]	(71.6)	(73.2)	(65.6)
Accumulated Other Comprehensive Income (Loss)
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Accumulated other comprehensive income (loss), beginning of period		(145.8)	(14.4)	99.5
Other Comprehensive Income (Loss) before Reclassifications Tax [Abstract]
Increase (decrease)		133.1	(137.6)	(114.1)
Income tax impact		0.9	2.0	(5.0)
Other comprehensive income (loss) before reclassifications, net of income taxes		134.0	(135.6)	(119.1)
Reclassification from AOCI, Current Period, Tax [Abstract]
Increase (decrease)		5.5	5.5	6.9
Income tax impact		(1.3)	(1.3)	(1.7)
Amounts reclassified from accumulated other comprehensive income (loss), net of income taxes		4.2	4.2	5.2
Total other comprehensive income (loss), net of income taxes		138.2	(131.4)	(113.9)
Accumulated other comprehensive income (loss), end of period		$ (7.6)	$ (145.8)	$ (14.4)

[1] Includes balances relating to non-U.S. employee defined benefit plans, supplemental executive retirement plans and other postretirement employee benefit plans.

[2] This accumulated other comprehensive income (loss) component is included in the computation of net periodic pension cost (refer to Note 10 for additional details).