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Restricted Stock and Stock Options - Additional Information (Detail) | 12 Months Ended
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Dec. 31, 2020 USD ($) Company shares | Dec. 31, 2019 USD ($) shares | Dec. 31, 2018 USD ($) shares | Dec. 31, 2017 USD ($) shares | Dec. 31, 2013 USD ($)
2005 Incentive Plan [Member] |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |
Duration for Stock option grants exercisable | 10 years |  |  |  |
Expiration of stock option | 90 days |  |  |  |
Unexercised portion of stock option remains exercisable | 1 year |  |  |  |
Number of companies used for the estimation of expected volatility | Company | 6 |  |  |  |
Dividend yield assumed | 0.00% |  |  |  |
Cash dividends paid | $ |  |  |  |  | $ 0
Compensation expense | $ | $ 0 | $ 0 | $ 12,000 |  |
2005 Incentive Plan [Member] | Restricted Stock [Member] |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |
Restricted stock outstanding | 0 |  |  |  |
2012 Equity and Incentive Compensation Plan [Member] |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |
Shares authorized under incentive plan | 500,000 |  |  |  |
Common stock granted | 23,207 | 9,391 |  |  |
Common stock available for future awards |  | 297,227 |  |  |
2012 Equity and Incentive Compensation Plan [Member] | Restricted Stock [Member] |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |
Common stock granted |  |  | 13,322 |  |
2012 Equity and Incentive Compensation Plan [Member] | Share Based Grants [Member] |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |
Compensation expense | $ | $ 605,000 |  | $ 676,000 | $ 726,000 |
2012 Equity and Incentive Compensation Plan [Member] | Long-Term Incentive Awards [Member] |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |
Compensation expense | $ | $ 2,341,000 |  | $ 1,359,000 | $ 976,000 |
Non-Employee Director Restricted Stock Plan [Member] |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |
Restricted stock outstanding | 5,068 | 4,890 | 5,761 | 6,454 |
Compensation expense | $ | $ 349,000 | $ 317,000 | $ 351,000 |  |
Shares authorized under incentive plan | 150,000 |  |  |  |
Common stock granted | 5,269 | 4,890 | 5,761 |  |
Common stock available for future awards | 47,748 |  |  |  |
Restricted stock award for a number of shares | $ | $ 50,000 |  |  |  |
Non-Employee Director Restricted Stock Plan [Member] | Restricted Stock [Member] | Maximum [Member] |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |
Increase in annual restricted stock award | $ | $ 75,000 |  |  |  |

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- Definition The estimated dividend rate (a percentage of the share price) to be paid (expected dividends) to holders of the underlying shares over the option's term. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (f)(2)(iii) -URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901 + Details
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