Income Taxes, Valuation Allowance for Deferred Tax Assets (Details) - Valuation Allowance of Deferred Tax Assets [Member] - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Valuation and Qualifying Accounts Disclosure [Line Items]
Valuation allowance for deferred tax assets at beginning of the period		$ 33.6	$ 23.8	$ 27.5
Revaluation and change due to U.S. Tax Reform		10.7	0.0	0.0
Charged to tax expense		3.1	12.5	4.8
Charged to other accounts		1.6	(0.1)	0.0
Deductions	[1]	(1.1)	(2.6)	(8.5)
Valuation allowance for deferred tax assets at end of the period		$ 47.9	$ 33.6	$ 23.8

[1] Deductions relate to the realization of net operating losses or the removal of deferred tax assets.