EARNINGS PER SHARE (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Numerator:
Net income (loss)	$ 61,352	$ 31,317	$ 117,196	$ 84,955
Denominator (shares in 000's):
Basic weighted average shares outstanding (in shares)	65,811,000	68,181,000	65,750,000	68,883,000
Effect of dilutive securities - Stock options and awards (in shares)	932,000	709,000	916,000	686,000
Diluted weighted average shares outstanding (in shares)	66,743,000	68,890,000	66,666,000	69,569,000
Earnings (loss) per share
Basic earnings (loss) per share (in dollars per share)	$ 0.93	$ 0.46	$ 1.78	$ 1.23
Diluted earnings (loss) per share (in dollars per share)	$ 0.92	$ 0.45	$ 1.76	$ 1.22
Anti-dilutive shares excluded from the computation of diluted earnings per share	179,178	810,200	133,748	750,209