EARNINGS PER SHARE (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Numerator:
Net income (loss)	$ 58,479	$ 72,461	$ 141,037	$ 229,393
Denominator (shares in 000's):
Basic weighted average shares outstanding (in shares)	59,426,000	61,380,000	59,655,000	62,282,000
Effect of dilutive securities - Stock options and awards (in shares)	592,000	681,000	547,000	690,000
Diluted weighted average shares outstanding (in shares)	60,018,000	62,061,000	60,202,000	62,972,000
Earnings (loss) per share
Basic earnings per share (Note 3)	$ 0.98	$ 1.18	$ 2.36	$ 3.68
Diluted earnings per share (Note 3)	$ 0.97	$ 1.17	$ 2.34	$ 3.64
Anti-dilutive shares excluded from the computation of diluted earnings per share	557,198	548,049	547,329	514,402