EARNINGS PER SHARE (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Numerator:
Net income (loss)	$ 60,824	$ 55,844
Denominator (shares in 000's):
Basic weighted average shares outstanding (in shares)	65,579,000	65,688,000
Effect of dilutive securities - Stock options and awards (in shares)	864,000	895,000
Diluted weighted average shares outstanding (in shares)	66,443,000	66,583,000
Earnings (loss) per share
Basic earnings (loss) per share (in dollars per share)	$ 0.93	$ 0.85
Diluted earnings (loss) per share (in dollars per share)	$ 0.92	$ 0.84
Anti-dilutive shares excluded from the computation of diluted earnings per share	174,325	88,220