Income Taxes Income Taxes - Rollforward of Deferred Tax Assets Valuation Allowance (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Valuation Allowance [Line Items]
Deferred Tax Assets, Valuation Allowance, Beginning Balance	$ 113.3	$ 135.7	$ 147.1
Deferred Tax Asset Valuation Allowance, Change in Assessment		(0.3)	(7.4)
Deferred Tax Asset Valuation Allowance, Current Year Operations	56.7	(22.1)	(4.0)
Deferred Tax Assets, Valuation Allowance, Ending Balance	170.0	113.3	135.7
Domestic Tax Authority [Member]
Valuation Allowance [Line Items]
Deferred Tax Assets, Valuation Allowance, Beginning Balance	0.0	0.0	0.0
Deferred Tax Asset Valuation Allowance, Change in Assessment		0.0	0.0
Deferred Tax Asset Valuation Allowance, Current Year Operations	0.0	0.0	0.0
Deferred Tax Assets, Valuation Allowance, Ending Balance	0.0	0.0	0.0
State and Local Jurisdiction [Member]
Valuation Allowance [Line Items]
Deferred Tax Assets, Valuation Allowance, Beginning Balance	45.9	41.5	45.0
Deferred Tax Asset Valuation Allowance, Change in Assessment		0.0	0.0
Deferred Tax Asset Valuation Allowance, Current Year Operations	26.5	4.4	(3.5)
Deferred Tax Assets, Valuation Allowance, Ending Balance	72.4	45.9	41.5
Foreign Tax Authority [Member]
Valuation Allowance [Line Items]
Deferred Tax Assets, Valuation Allowance, Beginning Balance	67.4	94.2	102.1
Deferred Tax Asset Valuation Allowance, Change in Assessment		(0.3)	(7.4)
Deferred Tax Asset Valuation Allowance, Current Year Operations	30.2	(26.5)	(0.5)
Deferred Tax Assets, Valuation Allowance, Ending Balance	$ 97.6	$ 67.4	$ 94.2