EARNINGS PER SHARE (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Numerator:
Net income (loss)	$ 106,126	$ 60,049	$ 223,322	$ 145,004
Denominator (shares in 000's):
Basic weighted average shares outstanding (in shares)	65,806,000	66,477,000	65,769,000	68,081,000
Effect of dilutive securities - Stock options and awards (in shares)	896,000	705,000	910,000	703,000
Diluted weighted average shares outstanding (in shares)	66,702,000	67,182,000	66,679,000	68,784,000
Earnings (loss) per share
Basic earnings (loss) per share (in dollars per share)	$ 1.61	$ 0.90	$ 3.40	$ 2.13
Diluted earnings (loss) per share (in dollars per share)	$ 1.59	$ 0.89	$ 3.35	$ 2.11
Anti-dilutive shares excluded from the computation of diluted earnings per share	182,615	803,741	149,888	807,763