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Stock-Based Compensation - Restricted Stock - Service-Based - Additional Information (Detail) - Service Based Restricted Stock [Member] - USD ($)
shares in Thousands, $ in Millions
3 Months Ended
Mar. 31, 2019
Mar. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Stock awards issued during the period 190,159  
Grants vesting period 3 years  
Restricted shares vested grant date intrinsic value $ 2.1 $ 0.8
Unrecognized compensation expense $ 3.0  
Weighted average period 1 year 6 months