EARNINGS PER SHARE (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Numerator for basic and diluted earnings per share:
Net income	$ 26,801	$ 35,361	$ 22,902	$ 10,502	$ 61,874	$ 12,359	$ 23,426	$ 32,015	$ 95,566	$ 129,674	$ 127,252
Denominator:
Basic shares outstanding									60,574	53,884	52,961
Dilutive effect of equity-based compensation awards									154	195	363
Dilutive shares outstanding									60,728	54,079	53,324
Basic earnings per share:
Basic earnings per share (in dollars per share)									$ 1.58	$ 2.41	$ 2.40
Diluted earnings per share:
Diluted earnings per share (in dollars per share)									$ 1.57	$ 2.40	$ 2.39