Annual report pursuant to Section 13 and 15(d)

Equity-Based Compensation - PSU awards (Details)

v3.19.3.a.u2
Equity-Based Compensation - PSU awards (Details) - USD ($)
$ / shares in Units, $ in Thousands
1 Months Ended 2 Months Ended 10 Months Ended 12 Months Ended 24 Months Ended
Jan. 31, 2020
Mar. 12, 2019
Dec. 31, 2019
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2016
Dec. 31, 2017
Number of units              
Granted (in shares) 4,644,934            
Vested (in shares)       (730,343)      
Weighted average grant date fair value              
Vested (in dollars per share)       $ 27.60      
Aggregate intrinsic value              
Outstanding at the beginning of the period $ 4,992 $ 12,470 $ 13,476 $ 12,470      
Outstanding at the end of the period   $ 13,476 $ 4,992 $ 4,992 $ 12,470    
Performance share unit awards              
Number of units              
Total awarded and unvested at the beginning of the period (in shares) 2,537,283 1,767,299   1,767,299      
Granted (in shares)       1,416,378      
Exercised (in shares)       (31,944)      
Vested (in shares)       (326,938)      
Forfeited (in shares)       (287,512)      
Total awarded and unvested at the end of the period (in shares)     2,537,283 2,537,283 1,767,299    
Weighted average grant date fair value              
Total awarded and unvested at the beginning of the period (in dollars per share) $ 16.74 $ 26.36   $ 26.36      
Granted (in dollars per share)       9.26      
Excercised (in dollars per share)       27.38      
Vested (in dollars per share)       32.97      
Forfeited (in dollars per share)       19.38      
Total awarded and unvested at the end of the period (in dollars per share)     $ 16.74 16.74 $ 26.36    
Weighted-average assumptions used to calculate fair value of performance share units granted              
Weighted average fair value of awards granted (in dollars per share)       $ 9.26      
Price target and TSR performance share unit awards              
Price target as a percentage of beginning price       125.00%      
Vesting period         3 years    
Amortization period of PSU expense         3 years    
Price target and TSR performance share unit awards | Minimum              
Number of PSUs that may be earned as compared to the number of PSUs granted, as a percent         0.00%    
Price target and TSR performance share unit awards | Maximum              
Number of PSUs that may be earned as compared to the number of PSUs granted, as a percent         200.00%    
Price target performance share unit awards              
Number of successive days closing stock price must achieve specific thresholds for PSUs to vest per schedule           10 days  
Vesting period       3 years      
Price target performance share unit awards | Vesting before first anniversary | Maximum              
Number of PSUs that may vest, as a percent           0.00%  
Price target performance share unit awards | Vesting before the second anniversary | Maximum              
Number of PSUs that may vest, as a percent           33.33%  
Price target performance share unit awards | Vesting before the third anniversary | Maximum              
Number of PSUs that may vest, as a percent       66.66%      
TSR performance share unit awards              
Price target as a percentage of beginning price       125.00%      
Vesting period       3 years     3 years
TSR performance share unit awards | Minimum              
Number of PSUs that may be earned as compared to the number of PSUs granted, as a percent       0.00%     0.00%
TSR performance share unit awards | Maximum              
Number of PSUs that may be earned as compared to the number of PSUs granted, as a percent       200.00%      
ROCE performance share unit awards              
Vesting period         3 years    
ROCE performance share unit awards | Minimum              
Number of PSUs that may vest, as a percent         0.00%    
ROCE performance share unit awards | Maximum              
Number of PSUs that may vest, as a percent         200.00%    
Market-Based PSUs              
Weighted average grant date fair value              
Granted (in dollars per share)       $ 9.26 $ 24.85    
Additional disclosures              
Additional equity compensation to be recognized over the remaining period     $ 17,000 $ 17,000      
Weighted average period for recognizing unrecognized stock-based compensation expense       1 year 9 months 18 days      
Weighted-average assumptions used to calculate fair value of performance share units granted              
Dividend yield (as a percent)         0.00%    
Volatility (as a percent)       36.00% 41.00%    
Risk-free interest rate (as a percent)       2.35% 2.49%    
Weighted average fair value of awards granted (in dollars per share)       $ 9.26 $ 24.85