XML 69 R58.htm IDEA: XBRL DOCUMENT v3.10.0.1
Stock-Based Compensation Plans - Additional Information (Detail) - USD ($)
$ in Millions
6 Months Ended
Jun. 30, 2018
Jun. 30, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Stock option compensation $ 1.9 $ 2.2
Stock Options Plan [Member]    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Number exercisable and fully vested 38,264  
Fully vested stock options with performance conditions attached 600  
Stock option compensation $ 1.9 2.2
Total intrinsic value exercised 2.2 2.0
Total compensation cost related to non-vested stock options not yet recognized $ 7.8  
Expected compensation cost recognized over the weighted-average period 2 years 29 days  
Stock Equivalent Units [Member]    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Fully vested stock options with performance conditions attached 27,655  
Total intrinsic value exercised $ 2.4 1.1
Expected compensation cost recognized over the weighted-average period 1 year 11 months 8 days  
Number of exercisable SEUs 30,360  
Compensation cost $ 5.3 $ 2.5