Weighted Average Exercise Prices for Options Granted and Exercisable and Weighted Average Remaining Contractual Life for Options Outstanding (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended
Mar. 31, 2015	Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Shares, Outstanding	697,854	724,904
Weighted Average Exercise Price, Outstanding	$ 9.21	$ 9.22
Weighted Average Exercisable, Exercise Price	$ 7.71	$ 7.82
Incentive Stock Option Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Shares, Outstanding	697,854
Number of Shares, Expected to Vest	686,973
Number of Shares, Exercisable	421,229
Weighted Average Exercise Price, Outstanding	$ 9.21
Weighted Average Exercise Price, Expected to Vest	$ 9.17
Weighted Average Exercisable, Exercise Price	$ 7.71
Weighted Average Remaining Life, Outstanding	87 months
Weighted Average Remaining Contractual Life, Expected to Vest	89 months
Weighted Average Remaining Contractual Life, Exercisable	71 months
Intrinsic Value, Outstanding	$ 1,262
Intrinsic Value, Expected to Vest	1,262
Intrinsic Value, Exercisable	$ 1,262
Performance Incentive Stock Option Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Shares, Outstanding	107,689	107,689
Number of Shares, Expected to Vest	107,689
Weighted Average Exercise Price, Outstanding	$ 11.49	$ 11.49
Weighted Average Exercise Price, Expected to Vest	$ 11.49
Weighted Average Remaining Life, Outstanding	33 months
Weighted Average Remaining Contractual Life, Expected to Vest	33 months
Weighted Average Remaining Contractual Life, Exercisable	0 months

Weighted Average Exercise Prices for Options Granted and Exercisable and Weighted Average Remaining Contractual Life for Options Outstanding (Detail) (USD $)
In Thousands, except Share data, unless otherwise specified

3 Months Ended

Mar. 31, 2015

Dec. 31, 2014

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Number of Shares, Outstanding

697,854us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber

724,904us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber

Weighted Average Exercise Price, Outstanding

$ 9.21us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice

$ 9.22us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice

Weighted Average Exercisable, Exercise Price

$ 7.71us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice

$ 7.82us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice

Incentive Stock Option Plan

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Number of Shares, Outstanding

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Number of Shares, Expected to Vest

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Number of Shares, Exercisable

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Weighted Average Exercise Price, Outstanding

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Weighted Average Exercise Price, Expected to Vest

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Weighted Average Exercisable, Exercise Price

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Weighted Average Remaining Life, Outstanding

87 months

Weighted Average Remaining Contractual Life, Expected to Vest

89 months

Weighted Average Remaining Contractual Life, Exercisable

71 months

Intrinsic Value, Outstanding

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Intrinsic Value, Expected to Vest

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Intrinsic Value, Exercisable

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Performance Incentive Stock Option Plan

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Number of Shares, Outstanding

107,689us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber
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Number of Shares, Expected to Vest

107,689us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingNumber
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Weighted Average Exercise Price, Outstanding

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Weighted Average Exercise Price, Expected to Vest

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Weighted Average Remaining Life, Outstanding

33 months

Weighted Average Remaining Contractual Life, Expected to Vest

33 months

Weighted Average Remaining Contractual Life, Exercisable

0 months

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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.

+ References

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

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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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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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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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As of the balance sheet date, the number of shares into which fully vested and expected to vest stock options outstanding can be converted under the option plan.

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As of the balance sheet date, the weighted-average exercise price for outstanding stock options that are fully vested or expected to vest.

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Weighted average remaining contractual term for fully vested and expected to vest options outstanding, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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