Annual report pursuant to Section 13 and 15(d)

Stock-Based Compensation - PSA Valuation Assumptions (Details)

v3.20.4
Stock-Based Compensation - PSA Valuation Assumptions (Details) - USD ($)
12 Months Ended
Mar. 24, 2020
Sep. 11, 2019
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Performance Share Awards (PSAs)          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value       $ 13.25 $ 13.97
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Grant Date Intrinsic Value $ 2.18 $ 7.43      
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Weighted Average Volatility Rate 66.29% 41.45%      
Risk-free rate of return 0.44% 1.59%      
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Dividend Payments $ 0 $ 0      
Restricted Stock Units (RSUs)          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period     165,000.0 622,800 308,300
Granted (in dollars per share)     $ 4.36 $ 7.39 $ 16.12
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value     $ 6.71 $ 8.28  
Number of shares accounted for as liability awards (in shares)     638,300 670,800  
Vested (in shares)     (131,600)    
Forfeited (in shares)     (65,900)    
Vested (in dollars per share)     $ 11.40    
Forfeited (in dollars per share)     $ 6.95    
Performance Shares, Performance Share Units and Restricted Stock Units          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period     691,100    
Granted (in dollars per share)     $ 0.90    
Share-based Compensation Arrangement by Share-based Payment Award, Options, Expirations in Period     (211,700)    
Share-based Compensation Arrangements by Share-based Payment Award, Options, Expirations in Period, Weighted Average Exercise Price     $ 16.54    
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value     $ 4.69 $ 10.53  
Number of shares accounted for as liability awards (in shares)     1,257,400 868,300  
Vested (in shares)     0    
Forfeited (in shares)     (90,300)    
Vested (in dollars per share)     $ 0    
Forfeited (in dollars per share)     $ 4.15