Schedule of Share Based Compensation Stock Options Activity (Detail) (USD $)	3 Months Ended
Mar. 31, 2015
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares, Outstanding Beginning Balance	67,375
Shares, Granted	53,500
Shares, Exercised	0
Shares, Forfeited	0
Shares, Expired	0
Shares, Outstanding Ending Balance	120,875
Shares, Exerciseable	36,281
Weighted-Average Exercise Price, Outstanding Beginning Balance	$ 26.05
Weighted-Average Exercise Price, Granted	$ 31.55
Weighted-Average Exercise Price, Exercised	$ 0
Weighted-Average Exercise Price, Forfeited	$ 0
Weighted-Average Exercise Price, Expired	$ 0
Weighted-Average Exercise Price, Oustanding Ending Balance	$ 28.49
Weighted-Average Exercise Price, Exerciseable	$ 26.29
Weighted-Average Remaining Contractual Life (Yrs), Outstanding	9 years 2 months 12 days
Weighted-Average Remaining Contractual Life (Yrs), Exerciseable	8 years 8 months 5 days
Aggregate Intrinsic Value, Outstanding	$ 264,084
Aggregate Intrinsic Value, Exerciseable	$ 137,633

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Amount of difference between fair value of the underlying shares reserved for issuance and exercise price of vested portions of options outstanding and currently exercisable.

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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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-Name Accounting Standards Codification

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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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- Definition

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

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Weighted average price at which grantees could have acquired the underlying shares with respect to stock options of the plan that expired.

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Weighted average price at which grantees could have acquired the underlying shares with respect to stock options that were terminated.

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

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