EARNINGS PER SHARE (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Numerator:
Net income	$ 53,395	$ 60,049	$ 31,317	$ 53,638	$ 48,692	$ (60,466)	$ 70,898	$ 68,354	$ 198,399	$ 127,478	$ 254,686
Denominator:
Basic weighted average shares outstanding (in shares)									67,462,000	74,111,000	79,185,000
Effect of dilutive securities - stock options and awards (in shares)									694,000	743,000	911,000
Diluted weighted average shares outstanding (in shares)									68,156,000	74,854,000	80,096,000
Basic earnings per share (in dollars per share)	$ 0.81	$ 0.90	$ 0.46	$ 0.77	$ 0.68	$ (0.82)	$ 0.95	$ 0.90	$ 2.94	$ 1.72	$ 3.22
Diluted earnings per share (in dollars per share)	$ 0.81	$ 0.89	$ 0.45	$ 0.76	$ 0.68	$ (0.82)	$ 0.94	$ 0.89	$ 2.91	$ 1.70	$ 3.18
Anti-dilutive shares excluded from the computation of diluted earnings per share									774,502	522,471	260,090