EARNINGS PER SHARE (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Numerator:
Net income	$ 48,692	$ (60,466)	$ 70,898	$ 68,354	$ 75,212	$ 45,689	$ 77,332	$ 56,453	$ 127,478	$ 254,686	$ 293,780
Denominator:
Basic weighted average shares outstanding (in shares)									74,111,000	79,185,000	81,978,000
Effect of dilutive securities - stock options and awards (in shares)									743,000	911,000	1,064,000
Diluted weighted average shares outstanding (in shares)									74,854,000	80,096,000	83,042,000
Basic earnings per share (in dollars per share)	$ 0.68	$ (0.82)	$ 0.95	$ 0.90	$ 0.97	$ 0.58	$ 0.97	$ 0.70	$ 1.72	$ 3.22	$ 3.58
Diluted earnings per share (in dollars per share)	$ 0.68	$ (0.82)	$ 0.94	$ 0.89	$ 0.96	$ 0.57	$ 0.96	$ 0.69	$ 1.70	$ 3.18	$ 3.54
Anti-dilutive shares excluded from the computation of diluted earnings per share									522,471	260,090	45,850