EARNINGS PER SHARE (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended	9 Months Ended
Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Numerator for basic and diluted earnings per share:
Net income	$ 35,361	$ 12,359	$ 68,765	$ 67,800
Denominator:
Basic shares outstanding (in shares)	60,610	53,374	60,542	53,303
Dilutive effect of equity-based compensation awards (in shares)	150	191	150	216
Dilutive shares outstanding (in shares)	60,760	53,565	60,692	53,519
Basic earnings per share:
Basic earnings per share (in USD per share)	$ 0.58	$ 0.23	$ 1.14	$ 1.27
Diluted earnings per share:
Diluted earnings per share (in USD per share)	$ 0.58	$ 0.23	$ 1.13	$ 1.27

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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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