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Stock-Based Compensation - Additional Information (Detail) - USD ($)
$ / shares in Units, $ in Millions
3 Months Ended 6 Months Ended 12 Months Ended
Mar. 31, 2018
Jun. 30, 2018
Jun. 30, 2017
Dec. 31, 2017
May 22, 2014
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]          
Maximum tenure of stock option from the date of grant   10 years      
Exercisable period of vested awards   30 days      
Minimum [Member]          
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]          
Stock options, Vesting period   1 year      
Maximum [Member]          
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]          
Stock options, Vesting period   5 years      
Restricted Stock [Member]          
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]          
Restricted stock awards granted 125,000 125,000   675,000  
Restricted stock fair value $ 16.35 $ 16.35      
Stock options, Vesting period 5 years 5 years      
Stock-based compensation expense   $ 2.6 $ 2.4    
Unrecognized stock compensation expense   $ 13.1      
Unrecognized stock compensation expense, weighted average period   2 years 8 months 12 days      
Omnibus Incentive Plan [Member]          
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]          
Common stock reserved for issuance         2,981,737
Shares available for grant   1,231,699