Stock-Based Compensation - Summary of the Status of the Stock Options (Detail) (USD $)	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Outstanding, Stock Option, Beginning balance	35,500
Stock option, Forfeited	(1,250)
Stock option, Exercised	(34,250)	(40,000)	(31,875)
Outstanding, Stock Option, Ending balance	0	35,500
Options vested and exercisable	0
Fair value of options granted during 2014	$ 0
Number of authorized stock-based awards available for grant	358,041
Outstanding Weighted-average Exercise Price, Beginning balance	$ 16.04
Weighted-average Exercise Price, Forfeited	$ 0
Weighted-average Exercise Price, Exercised	$ 16.04
Outstanding Weighted-average Exercise Price, Ending balance	$ 0	$ 16.04

Share-based compensation arrangement by share-based payment award options granted in period fair value.

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- Definition

The difference between the maximum number of shares (or other type of equity) authorized for issuance under the plan (including the effects of amendments and adjustments), and the sum of: 1) the number of shares (or other type of equity) already issued upon exercise of options or other equity-based awards under the plan; and 2) shares (or other type of equity) reserved for issuance on granting of outstanding awards, net of cancellations and forfeitures, if applicable.

+ References

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- Definition

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.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (c)(1)(iv)(3)

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- Definition

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

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-Publisher FASB

-Name Accounting Standards Codification

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- Definition

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

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- Definition

The number of exercisable share options (fully vested and expected to vest) that may be converted as of the balance sheet date.

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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 that were terminated.

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

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 04

-Article 3

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