Annual report pursuant to Section 13 and 15(d)

Stock-Based Compensation - Stock-Based Awards (Details)

v3.8.0.1
Stock-Based Compensation - Stock-Based Awards (Details) - USD ($)
$ / shares in Units, $ in Millions
12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award, Additional General Disclosures [Abstract]      
Stock award vesting period 3 years    
Nonvested RSUs      
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]      
Nonvested, Beginning Balance (in shares) 5,333,522    
Granted (in shares) 2,711,546 3,289,569 2,996,151
Vested (in shares) (2,512,552)    
Forfeited (in shares) (998,338)    
Nonvested, Ending Balance (in shares) 4,534,178 5,333,522  
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]      
Nonvested, Beginning Balance (in dollars per share) $ 2.85    
Granted (in dollars per share) 1.42 $ 2.07 $ 3.08
Vested (in dollars per share) 3.41    
Forfeited (in dollars per share) 2.29    
Nonvested, Ending Balance (in dollars per share) $ 1.81 $ 2.85  
Allocated share-based compensation expense $ 4.0 $ 7.5 $ 8.4
Fair value of units vested in period 8.6 $ 10.0 $ 8.0
Unrecognized compensation cost $ 3.3    
Weighted-average vesting period 33 months    
Time-Based Phantom Stock Units      
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]      
Nonvested, Beginning Balance (in shares) 985,938    
Granted (in shares) 648,755 1,188,854 0
Vested (in shares) (299,796)    
Forfeited (in shares) (216,793)    
Nonvested, Ending Balance (in shares) 1,118,104 985,938  
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]      
Allocated share-based compensation expense $ 0.0 $ 1.4  
2010 Long-Term Incentive Plan      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Number of shares authorized under stock plan 16,800,000    
2010 Long-Term Incentive Plan | Common Stock      
Share-based Compensation Arrangement by Share-based Payment Award, Additional General Disclosures [Abstract]      
Share remaining available under Stock Plan 4,617,521