Annual report pursuant to Section 13 and 15(d)

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

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Income Taxes, Tax Credits and Unrecognized Tax Benefits (Details) - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Income Tax Disclosure [Abstract]      
Gross Unrecognized Tax Benefits, Including Interest $ 3.9 $ 2.3 $ 2.3
Reconciliation of the total amounts of unrecognized tax benefits [Roll Forward]      
Balance at January 1 2.3 2.1 3.4
Gross Increases - Tax Positions Prior Periods 2.0 0.6 0.1
Gross Decreases - Tax Positions Prior Periods (0.8) (0.7) (0.2)
Gross Increases - Current Period Tax Positions 0.4 0.4 0.4
Decreases - Settlements with Taxing Authorities 0.0 (0.1) (0.5)
Reductions - Lapse of Statute of Limitations (0.2) 0.0 (1.1)
Balance at December 31 3.7 2.3 $ 2.1
Possible Decrease in Unrecognized Tax Benefits in 2017 0.6    
Tax Credit Carryforward [Line Items]      
Tax Credit Carryforward, Amount 73.6    
Tax Credit Carryforwards 71.8 $ 53.2  
Tax Credit Carryforward, Expiration Date 73.6    
General Business Credits [Member]      
Tax Credit Carryforward [Line Items]      
Tax Credit Carryforwards 31.0    
State Tax Credits [Member]      
Tax Credit Carryforward [Line Items]      
Tax Credit Carryforwards $ 42.6