Income Taxes, Tax Credit Carryforwards (Details) $ in Millions	12 Months Ended
	Dec. 31, 2017 USD ($)
Tax Credit Carryforward [Line Items]
Alternative minimum tax credit	$ 0.9
Other deferred tax assets, tax benefit	5.3
Other deferred tax assets, valuation allowance	(0.1)
Total tax carryforwards, tax benefit	78.8
Total tax carryforwards, valuation allowance	(47.9)
U.S. Federal [Member]
Tax Credit Carryforward [Line Items]
Tax credit, tax benefit	33.4
Tax credit, valuation allowance	$ (29.9)
U.S. Federal [Member] | Minimum [Member]
Tax Credit Carryforward [Line Items]
Tax credit, expiration date	Dec. 31, 2023
U.S. Federal [Member] | Maximum [Member]
Tax Credit Carryforward [Line Items]
Tax credit, expiration date	Dec. 31, 2037
U.S. State and Local [Member]
Tax Credit Carryforward [Line Items]
Tax credit, tax benefit	$ 0.5
Tax credit, valuation allowance	$ 0.0
U.S. State and Local [Member] | Minimum [Member]
Tax Credit Carryforward [Line Items]
Tax credit, expiration date	Dec. 31, 2018
U.S. State and Local [Member] | Maximum [Member]
Tax Credit Carryforward [Line Items]
Tax credit, expiration date	Dec. 31, 2034
Capital Losses [Member] | U.S. Federal [Member]
Tax Credit Carryforward [Line Items]
Tax credit, tax benefit	$ 6.9
Tax credit, valuation allowance	$ (6.9)
Tax credit, expiration date	Dec. 31, 2021
Capital Losses [Member] | Non U.S. [Member]
Tax Credit Carryforward [Line Items]
Tax credit, tax benefit	$ 0.5
Tax credit, valuation allowance	$ (0.5)