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Share-based Compensation - Additional Information (Detail) - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]      
Exercise period of options 10 years    
Non-Employee Directors [Member]      
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]      
Non-employee director compensation grant period 5 days    
Maximum [Member] | Graded and Cliff Vesting [Member]      
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]      
Vesting period of options 5 years    
2015 Plan [Member]      
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]      
Shares available for grant 400,000    
Long Term Incentive Plan [Member]      
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]      
Performance target for achievement period 3 years    
Long Term Incentive Plan [Member] | Minimum [Member]      
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]      
Percentage of performance target for achievement 0.00%    
Long Term Incentive Plan [Member] | Maximum [Member]      
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]      
Percentage of performance target for achievement 150.00%    
Stock Compensation Plans [Member]      
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]      
Share-based compensation expense $ 5.6 $ 5.1 $ 5.3
Unrecognized share-based compensation expense $ 6.6    
Period of recognition of share-based compensation expense 2 years    
Stock Compensation Plans [Member] | 2015 Plan [Member]      
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]      
Maximum aggregate number of shares 1,550,000    
Shares available for grant 900,000    
Plan description As of December 31, 2020, subject to adjustments as provided in the 2015 Plan, the maximum aggregate number of shares of the Company’s common stock that could be issued under the 2015 Plan could not exceed the sum of (i) 1.55 million shares plus (ii) any shares (A) remaining available for the grant of awards as of the 2015 Plan effective date (April 22, 2015) under the 2007 Plan or the 2011 Plan, and/or (B) subject to an award granted under the 2007 Plan or the 2011 Plan, which award is forfeited, cancelled, terminated, expires, or lapses without the issuance of shares or pursuant to which such shares are forfeited. As of the effective date of the 2015 Plan (April 22, 2015), there were 0.9 million shares available for grant under the 2015 Plan, inclusive of shares previously available for grant under the 2007 Plan and the 2011 Plan that were rolled over to the 2015 Plan.    
Restricted Stock [Member] | Long Term Incentive Plan [Member]      
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]      
Performance target for achievement period 1 year    
Vesting period of options 2 years    
Deferred compensation arrangement with individual, description Each participant in the program is eligible to earn an RSA, subject to performance over a one-year period. Payout under the program can range from 0% to 150% of target based on the achievement of five Company performance metrics and individual performance goals (subject to continued employment and certain other terms and conditions of the program)    
Restricted Stock [Member] | Long Term Incentive Plan [Member] | Minimum [Member]      
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]      
Percentage of performance target for achievement 0.00%    
Restricted Stock [Member] | Long Term Incentive Plan [Member] | Maximum [Member]      
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]      
Percentage of performance target for achievement 150.00%