Stock Option Activity (Detail) (USD $)	9 Months Ended	12 Months Ended
Sep. 30, 2013	Dec. 31, 2012
Number of Options
Outstanding at December 31, 2012	682,141
Exercised	0
Expired	0
Forfeited	0
Granted	350,000
Outstanding at September 30, 2013	1,032,141	682,141
Outstanding exercisable at September 30, 2013	382,675
Weighted Average Exercise Price
Outstanding at December 31, 2012	$ 6.47
Exercised	$ 0
Expired	$ 0
Forfeited	$ 0
Granted	$ 6.25
Outstanding at September 30, 2013	$ 6.39	$ 6.47
Outstanding exercisable at September 30, 2013	$ 6.84
Weighted Average Remaining Contract Life
Outstanding at December 31, 2012	8 years 5 months 8 days	7 years 8 months 8 days
Outstanding at September 30, 2013	8 years 5 months 8 days	7 years 8 months 8 days
Outstanding exercisable at September 30, 2013	6 years 11 months 19 days
Aggregate Intrinsic Value
Outstanding at December 31, 2012	$ 88,000
Outstanding at September 30, 2013	117,338	88,000
Outstanding exercisable at September 30, 2013	$ 68,276

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The number of shares into which fully or partially vested stock options outstanding as of the balance sheet date can be currently converted under the option plan.

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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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Weighted average remaining contractual term for vested portions of options outstanding and currently exercisable or convertible, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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

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

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Weighted average price at which grantees can acquire the shares reserved for issuance under the stock option plan.

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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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Amount of difference between fair value of the underlying shares reserved for issuance and exercise price of fully vested and expected to vest options that are exercisable.

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Amount by which the current fair value of the underlying stock exceeds the exercise price of fully vested and expected to vest options outstanding.

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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 per share amount at which grantees can acquire shares of common stock by exercise of options.

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