Annual report pursuant to Section 13 and 15(d)

Share-Based Compensation and Other Benefit Plans - Activity of Awarded Restricted Stock Units (Detail)

v3.20.4
Share-Based Compensation and Other Benefit Plans - Activity of Awarded Restricted Stock Units (Detail) - USD ($)
$ / shares in Units, $ in Millions
12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Restricted Stock Units (RSUs)      
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]      
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period, Fair Value $ 2.8 $ 3.0 $ 3.3
Number of shares      
Balance at beginning of year (in shares) 136,876    
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period 281,382    
Vested (in shares) (63,916)    
Forfeited (in shares) (35,062)    
Balance at end of year (in shares) 319,280 136,876  
Weighted-Average Grant Date Fair Value      
Balance at beginning of year (in dollars per share) $ 49.76    
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value 4.49    
Vested (in dollars per share) 43.30    
Forfeited (in dollars per share) 27.83    
Balance at end of year (in dollars per share) $ 13.56 $ 49.76  
Performance Restricted Stock Units [Domain]      
Number of shares      
Balance at beginning of year (in shares) 79,914    
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period 145,399    
Vested (in shares) (31,146)    
Forfeited (in shares) (20,635)    
Balance at end of year (in shares) 173,532 79,914  
Weighted-Average Grant Date Fair Value      
Balance at beginning of year (in dollars per share) $ 52.73    
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value 7.79    
Vested (in dollars per share) 58.35    
Forfeited (in dollars per share) 55.99    
Balance at end of year (in dollars per share) $ 13.68 $ 52.73  
Performance Restricted Stock Units [Domain] | Share-based Payment Arrangement, Tranche One [Member]      
Weighted-Average Grant Date Fair Value      
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value   $ 34.02  
Performance Shares [Member]      
Weighted-Average Grant Date Fair Value      
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Dividend Rate 0.00% 0.00%  
Risk-free interest rate, max 0.51%    
Risk-free interest rate, min 0.18% 1.66%  
Expected volatility, min 101.32% 49.90%  
Expected volatility, max 117.71%    
Minimum [Member] | Performance Restricted Stock Units [Domain]      
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]      
Share-based Compensation Arrangement by Share-based Payment Award, Shares, Expected to Vest, Percentage 0.00%    
Minimum [Member] | Performance Restricted Stock Units [Domain] | Share-based Payment Arrangement, Tranche One [Member]      
Weighted-Average Grant Date Fair Value      
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value $ 2.40    
Maximum [Member] | Performance Restricted Stock Units [Domain]      
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]      
Share-based Compensation Arrangement by Share-based Payment Award, Shares, Expected to Vest, Percentage 200.00%    
Maximum [Member] | Performance Restricted Stock Units [Domain] | Share-based Payment Arrangement, Tranche One [Member]      
Weighted-Average Grant Date Fair Value      
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value $ 16.02