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Performance Awards - Additional Information (Detail) - USD ($)
$ in Thousands
3 Months Ended 6 Months Ended
Jun. 30, 2017
Jun. 30, 2016
Jun. 30, 2017
Jun. 30, 2016
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]        
Unearned compensation $ 2,800   $ 2,800  
Performance Awards        
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]        
Compensation expense 300 $ 200 600 $ 300
Unearned compensation $ 1,714 $ 1,500 $ 1,714 $ 1,500
2014 Equity Incentive Plan | Performance Awards        
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]        
Performance period     3 years