Note 6 - Earnings Per Common Share (Details) - Basic and Diluted Earnings Per Common Share (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended	12 Months Ended
Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Numerator:
Net income (in Dollars)	$ 8,969us-gaap_NetIncomeLoss	$ 7,652us-gaap_NetIncomeLoss	$ 7,926us-gaap_NetIncomeLoss	$ 5,287us-gaap_NetIncomeLoss	$ 7,301us-gaap_NetIncomeLoss	$ 7,977us-gaap_NetIncomeLoss	$ 7,667us-gaap_NetIncomeLoss	$ 7,202us-gaap_NetIncomeLoss	$ 29,834us-gaap_NetIncomeLoss	$ 30,147us-gaap_NetIncomeLoss	$ 27,267us-gaap_NetIncomeLoss
Denominator:
Basic earnings per common share - weighted-average shares									33,381	33,221	33,095
Effect of dilutive stock options									297	208	130
Diluted earnings per common share - weighted-average shares and assumed conversions									33,678	33,429	33,225
Basic earnings per common share (in Dollars per share)	$ 0.27us-gaap_EarningsPerShareBasic	$ 0.23us-gaap_EarningsPerShareBasic	$ 0.24us-gaap_EarningsPerShareBasic	$ 0.16us-gaap_EarningsPerShareBasic	$ 0.22us-gaap_EarningsPerShareBasic	$ 0.24us-gaap_EarningsPerShareBasic	$ 0.23us-gaap_EarningsPerShareBasic	$ 0.22us-gaap_EarningsPerShareBasic	$ 0.89us-gaap_EarningsPerShareBasic	$ 0.91us-gaap_EarningsPerShareBasic	$ 0.82us-gaap_EarningsPerShareBasic
Diluted earnings per common share (in Dollars per share)	$ 0.27us-gaap_EarningsPerShareDiluted	$ 0.23us-gaap_EarningsPerShareDiluted	$ 0.24us-gaap_EarningsPerShareDiluted	$ 0.16us-gaap_EarningsPerShareDiluted	$ 0.22us-gaap_EarningsPerShareDiluted	$ 0.24us-gaap_EarningsPerShareDiluted	$ 0.23us-gaap_EarningsPerShareDiluted	$ 0.22us-gaap_EarningsPerShareDiluted	$ 0.89us-gaap_EarningsPerShareDiluted	$ 0.90us-gaap_EarningsPerShareDiluted	$ 0.82us-gaap_EarningsPerShareDiluted

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The amount of net income (loss) for the period per each share of common stock or unit outstanding during the reporting period.

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The amount of net income (loss) for the period available to each share of common stock or common unit outstanding during the reporting period and to each share or unit that would have been outstanding assuming the issuance of common shares or units for all dilutive potential common shares or units outstanding during the reporting period.

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Additional shares included in the calculation of diluted EPS as a result of the potentially dilutive effect of share based payment arrangements using the treasury stock method.

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The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

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The average number of shares or units issued and outstanding that are used in calculating diluted EPS or earnings per unit (EPU), determined based on the timing of issuance of shares or units in the period.

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