XML 175 R122.htm IDEA: XBRL DOCUMENT v3.21.1
Share-based Payments - Additional Information (Detail) - USD ($)
$ / shares in Units, $ in Millions
12 Months Ended
Jul. 31, 2020
Feb. 28, 2020
Jul. 31, 2019
Feb. 28, 2019
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Disclosure of terms and conditions of share-based payment arrangement [line items]              
Share-based compensation expense         $ 5.3 $ 6.1 $ 7.1
Fair value of non-vested stock awards $ 93.99 $ 93.99 $ 96.46 $ 96.46      
Estimated compensation cost for next year         $ 1.9 $ 4.0  
Weighted average remaining contractual life         1 year 7 months 6 days 2 years 1 month 6 days  
Expected term         10 years    
Bottom of range [member]              
Disclosure of terms and conditions of share-based payment arrangement [line items]              
Vesting period         3 years    
Top of range [member]              
Disclosure of terms and conditions of share-based payment arrangement [line items]              
Vesting period         5 years    
2017 [member]              
Disclosure of terms and conditions of share-based payment arrangement [line items]              
Estimated compensation cost for next year         $ 1.4