Stock Plans - Summary of Stock Option Activity (Detail) - USD ($)	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016
Amended and Restated 2014 Stock Option and Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Shares Outstanding, Beginning Balance	666,208	405,190
Number of Shares , Granted	78,750	289,125
Number of Shares , Exercised		(21,107)
Number of Shares , Cancelled	(223,062)	(7,000)
Number of Shares Outstanding, Ending Balance	521,896	666,208
Number of Shares, Vested and exercisable	335,230
Weighted-average years remaining on contractual life	7 years 9 months 18 days
Unrecognized compensation cost related to non-vested stock options	$ 3,459,000
Weighted Average Exercise Price Per Share, Beginning Balance	$ 24.64	$ 19.80
Weighted Average Exercise Price Per Share, Granted	7.20	31.08
Weighted Average Exercise Price Per Share, Exercised		18.84
Weighted Average Exercise Price Per Share, Cancelled	27.04	27.16
Weighted Average Exercise Price Per Share, Ending Balance	20.96	$ 24.64
Weighted Average Exercise Price Per Share, Vested and exercisable	$ 20.36
Aggregate Intrinsic Value, Outstanding Beginning Balance	$ 2,064,000
Aggregate Intrinsic Value, Outstanding Ending Balance	255,000	$ 2,064,000
Aggregate Intrinsic Value, Vested and exercisable	$ 128,000
2004 Stock Option Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Shares Outstanding, Beginning Balance	2,656	2,729
Number of Shares, Expired	(570)
Number of Shares , Cancelled	(462)	(73)
Number of Shares Outstanding, Ending Balance	1,624	2,656
Number of Shares, Vested and exercisable	1,624
Weighted-average years remaining on contractual life	7 months 28 days
Unrecognized compensation cost related to non-vested stock options	$ 0
Weighted Average Exercise Price Per Share, Beginning Balance	$ 162.32	$ 162.32
Weighted Average Exercise Price Per Share, Expired	162.32
Weighted Average Exercise Price Per Share, Cancelled	162.32	162.32
Weighted Average Exercise Price Per Share, Ending Balance	$ 162.32	$ 162.32
Aggregate Intrinsic Value, Outstanding Ending Balance	$ 0
Weighted Average Exercise Price Per Share, Vested and exercisable	$ 162.32

Unrecognized cost of unvested options awarded to employees as compensation.

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The weighted-average price as of the balance sheet date at which grantees can acquire the shares reserved for issuance on vested portions of options outstanding and currently exercisable under the stock option plan.

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Number of options or other stock instruments for which the right to exercise has lapsed under the terms of the plan agreements.

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The number of shares under options that were cancelled during the reporting period as a result of occurrence of a terminating event specified in contractual agreements pertaining to the stock option plan.

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Gross number of share options (or share units) granted during the period.

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Amount by which the current fair value of the underlying stock exceeds the exercise price of options outstanding.

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Number of options outstanding, including both vested and non-vested options.

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Number of fully vested and expected to vest exercisable options that may be converted into shares under option plan. Includes, but is not limited to, unvested options for which requisite service period has not been rendered but that are expected to vest based on achievement of performance condition, if forfeitures are recognized when they occur.

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Amount by which current fair value of underlying stock exceeds exercise price of fully vested and expected to vest options outstanding. Includes, but is not limited to, unvested options for which requisite service period has not been rendered but that are expected to vest based on achievement of performance condition, if forfeitures are recognized when they occur.

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Weighted average price at which option holders acquired shares when converting their stock options into shares.

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Weighted average remaining contractual term for option awards outstanding, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Number of share options (or share units) exercised during the current period.

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