Stock Option Plans - Stock Option Activity (Details) (USD $)	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Options outstanding at the beginning of the year	1,236,063	1,118,688
Options granted	214,500	220,500
Options forfeited	(2,500)	(27,475)
Options exercised	(90,250)	(75,650)
Options outstanding at the end of the year	1,357,813	1,236,063
Options exercisable at the end of the year	880,743	771,208
Common stock available for future grants at the end of the year	36,475	38,975
Granted	$ 16.68	$ 13.38
Forfeited	$ 14.22	$ 12.17
Exercised	$ 12.62	$ 6.89
Outstanding	$ 12.35	$ 11.61
Exercisable	$ 11.53	$ 11.64

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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.

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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

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)(iii)

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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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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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No definition available.

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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 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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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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-Name Regulation S-X (SX)

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