EARNINGS (LOSS) PER SHARE (Reconciliation of Basic and Diluted Earnings Per Share Computations) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Numerator for basic and diluted (loss) earnings per share:
Net (loss) income	$ 84,194	$ 12,058	$ 25,880	$ (21,393)	$ (12,713)	$ (10,255)	$ 3,966	$ (20,871)	$ 100,739	$ (39,873)	$ 44,102
Denominator:
Weighted basic shares outstanding (in shares)									57,072	57,532	58,324
Dilutive effect of equity-based compensation awards (in shares)									128	0	110
Weighted dilutive shares outstanding (in shares)									57,200	57,532	58,434
Basic earnings (loss) per share (in dollars per share)									$ 1.77	$ (0.69)	$ 0.76
Diluted earnings (loss) per share (in dollars per share)									$ 1.76	$ (0.69)	$ 0.76