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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.