Income Taxes Amounts and Expiration Dates of Net Operating Loss and Tax Credit Carryforwards (Details) $ in Millions	12 Months Ended
	Dec. 31, 2016 USD ($)
Operating Loss Carryforwards [Line Items]
State net operating loss and tax credit carryforwards	$ 53.6
State net operating loss valuation allowance	(20.6)
U.S. net operating loss	109.1
U.S. alternative minimum tax credit	19.5
Total tax credit carryforwards	$ 161.6
State [Member]
Operating Loss Carryforwards [Line Items]
Operating Loss Carryforwards Minimum Expiration Date	2017
Operating Loss Carryforwards Maximum Expiration Date	2033
U.S. (Federal) [Member]
Operating Loss Carryforwards [Line Items]
Operating Loss Carryforwards Maximum Expiration Date	2036