XML 66 R55.htm IDEA: XBRL DOCUMENT v3.19.1
Share-Based Compensation - Narrative (Detail) - USD ($)
$ / shares in Units, shares in Millions, $ in Millions
1 Months Ended 3 Months Ended
Mar. 31, 2019
Mar. 31, 2019
Mar. 31, 2018
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]      
Share-based compensation   $ 3.4 $ 1.2
Restricted stock units      
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]      
Annual share-based compensation grants 0.6    
Grant date fair value $ 4.77    
Graded vesting period 3 years    
Dividend payable $ 0.0 $ 0.0  
Performance share units      
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]      
Annual share-based compensation grants 0.6    
Grant date fair value $ 4.77    
Cliff vesting period 34 months    
Phantom restricted stock units      
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]      
Annual share-based compensation grants   1.3  
Grant date share price $ 5.03 $ 5.03  
Payment description   payable in three equal installments over a period of three years after the grant date  
Payment term   3 years  
Phantom performance stock units      
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]      
Annual share-based compensation grants   0.4  
Cliff vesting period   34 months  
Grant date share price $ 5.03 $ 5.03  
Phantom stock units      
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]      
Dividend payable $ 0.0 $ 0.0