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Income Taxes - Additional Information (Detail) - USD ($) | 12 Months Ended
--- | ---
Dec. 31, 2015 | Dec. 31, 2014 | Dec. 31, 2013
Operating Loss Carryforwards [Line Items] |  |  |
Federal NOL carryforward assets utilized | $ 3,700,000 |  |
Cumulative federal NOL carryforward assets available to offset against taxes payable | 11,300,000 |  |
Alternative Minimum tax credit carryforwards | 2,677,000 | $ 2,139,000 |
Income tax benefit | 15,443,000 | $ 13,995,000 | $ 12,652,000
Federal Research and Development Tax Credit | 2014 expenditures |  |  |
Operating Loss Carryforwards [Line Items] |  |  |
Income tax benefit | 63,000 |  |
Federal Research and Development Tax Credit | 2015 expenditures |  |  |
Operating Loss Carryforwards [Line Items] |  |  |
Income tax benefit | $ 288,000 |  |
Internal Revenue Service (IRS) |  |  |
Operating Loss Carryforwards [Line Items] |  |  |
NOL carryforward assets expiration date | 2029 |  |
Federal |  |  |
Operating Loss Carryforwards [Line Items] |  |  |
Tax examination description | The Company remains subject to examination by Federal, Maine, Massachusetts, and New Hampshire tax authorities for the tax periods ended December 31, 2012; December 31, 2013; and December 31, 2014. |  |

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