Annual report pursuant to Section 13 and 15(d)

Income Taxes, Tax Credits and Unrecognized Tax Benefits (Details)

v3.8.0.1
Income Taxes, Tax Credits and Unrecognized Tax Benefits (Details) - USD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Income Tax Disclosure [Abstract]      
Gross Unrecognized Tax Benefits, Including Interest $ 2.3 $ 3.5 $ 4.8
Reconciliation of the total amounts of unrecognized tax benefits [Roll Forward]      
Balance at January 1 3.4 4.7 4.8
Gross Increases - Tax Positions Prior Periods 0.1 0.3 0.4
Gross Decreases - Tax Positions Prior Periods (0.2) (0.4) (0.1)
Gross Increases - Current Period Tax Positions 0.4 0.5 0.5
Decreases - Settlements with Taxing Authorities (0.5) 0.0 (0.6)
Reductions - Lapse of Statute of Limitations (1.1) (1.7) 0.0
Other 0.0 0.0 (0.3)
Balance at December 31 2.1 3.4 $ 4.7
Possible Decrease in Unrecognized Tax Benefits in 2017 0.7    
Tax Credit Carryforward [Line Items]      
Tax Credit Carryforward, Amount 43.8    
Tax Credit Carryforwards 43.8 $ 47.3  
Tax Credit Carryforward, Expiration Date 43.6    
Tax Credit Carryforwards, Not Subject to Expiration 0.2    
General Business Credits [Member]      
Tax Credit Carryforward [Line Items]      
Tax Credit Carryforwards 2.4    
State Tax Credits [Member]      
Tax Credit Carryforward [Line Items]      
Tax Credit Carryforwards $ 41.4