EARNINGS PER SHARE (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended	12 Months Ended
Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014
EARNINGS PER SHARE [Abstract]
Weighted-average anti-dilutive stock options outstanding (in shares)	300,000	40,000
Basic earnings per share [Abstract]
Net income	$ 22,297us-gaap_NetIncomeLoss	$ 22,173us-gaap_NetIncomeLoss
Income attributable to unvested stock-based compensation awards	(100)	(99)
Income available to common shareholders	22,197	22,074
Weighted-average common shares outstanding - basic (in shares)	40,659,000	40,458,000
Basic earnings per share (in dollars per share)	$ 0.55us-gaap_EarningsPerShareBasic	$ 0.55us-gaap_EarningsPerShareBasic
Diluted earnings per share [Abstract]
Net income	22,297us-gaap_NetIncomeLoss	22,173us-gaap_NetIncomeLoss
Income attributable to unvested stock-based compensation awards	(100)	(99)
Income available to common shareholders	$ 22,197	$ 22,074
Weighted-average common shares outstanding - basic (in shares)	40,659,000	40,458,000
Assumed exercise of stock options (in shares)	405,000	512,000
Weighted-average common shares outstanding - diluted (in shares)	41,064,000	40,970,000
Diluted earnings per share (in dollars per share)	$ 0.54us-gaap_EarningsPerShareDiluted	$ 0.54us-gaap_EarningsPerShareDiluted
Stock Repurchase Program [Abstract]
Number of common shares authorized to be repurchased (in shares)			2,000,000
Number of common shares repurchased (in shares)	265,230us-gaap_TreasuryStockSharesAcquired		123,000us-gaap_TreasuryStockSharesAcquired

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Amount of increase (decrease) to net income used for calculating diluted earnings per share (EPS), resulting from the assumed exercise of stock options or restrictive stock units (RSUs).

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Securities (including those issuable pursuant to contingent stock agreements) that could potentially dilute basic earnings per share (EPS) or earnings per unit (EPU) in the future that were not included in the computation of diluted EPS or EPU because to do so would increase EPS or EPU amounts or decrease loss per share or unit amounts for the period presented.

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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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Net income after adjustments for dividends on preferred stock (declared in the period) and/or cumulative preferred stock (accumulated for the period).

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The number of shares authorized to be repurchased by an entity's Board of Directors under a stock repurchase plan.

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Number of shares that have been repurchased during the period and are being held in treasury.

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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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Number of [basic] shares or units, after adjustment for contingently issuable shares or units and other shares or units not deemed outstanding, determined by relating the portion of time within a reporting period that common shares or units have been outstanding to the total time in that period.

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