Annual report pursuant to Section 13 and 15(d)

Summary of Significant Accounting Policies Summary of Significant Accounting Policies - Expected Impact of Adoption on Results of Operations (Details)

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Summary of Significant Accounting Policies Summary of Significant Accounting Policies - Expected Impact of Adoption on Results of Operations (Details) - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
New Accounting Pronouncements or Change in Accounting Principle [Line Items]      
Increase to accumulated deficit $ (31.8) $ 10.0  
Operating income (loss) (47.0) 18.9 $ (14.0)
Other expense, net 0.2 5.8 $ 3.6
Scenario, Previously Reported      
New Accounting Pronouncements or Change in Accounting Principle [Line Items]      
Operating income (loss)   18.9  
ASU 2017-07      
New Accounting Pronouncements or Change in Accounting Principle [Line Items]      
Operating income (loss) (42.5) 20.7  
Other expense, net 4.7 7.6  
ASU 2017-07 | Scenario, Previously Reported      
New Accounting Pronouncements or Change in Accounting Principle [Line Items]      
Operating income (loss) (47.0)    
Other expense, net 0.2 5.8  
ASU 2017-07 | Scenario, Adjustment      
New Accounting Pronouncements or Change in Accounting Principle [Line Items]      
Impact of Adoption 4.5 $ 1.8  
ASU 2018-02 | Pro Forma      
New Accounting Pronouncements or Change in Accounting Principle [Line Items]      
Increase to accumulated deficit 13.4    
Difference between Revenue Guidance in Effect before and after Topic 606 [Member] | Maximum | ASU 2014-09 | Pro Forma      
New Accounting Pronouncements or Change in Accounting Principle [Line Items]      
Increase to accumulated deficit $ 5.0