NET INCOME PER COMMON SHARE (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Basic (loss) income per share
Net income (loss)	$ (30,677)	$ (11,785)	$ (21,653)	$ (11,633)	$ 94,623	$ 6,454	$ 12,746	$ 17,939	$ (75,738)	$ 131,762	$ 43,313
Denominator for basic income (loss) per share (in shares)									60,116,530	58,292,633	56,736,009
Basic net income (loss) per share (in dollars per share)	$ (0.51)	$ (0.20)	$ (0.36)	$ (0.20)	$ 1.61	$ 0.11	$ 0.22	$ 0.31	$ (1.26)	$ 2.26	$ 0.76
Numerator:
Net income (loss)	$ (30,677)	$ (11,785)	$ (21,653)	$ (11,633)	$ 94,623	$ 6,454	$ 12,746	$ 17,939	$ (75,738)	$ 131,762	$ 43,313
Add interest expense on convertible debt, net of tax										4,256
Net income (loss), diluted									$ (75,738)	$ 136,018	$ 43,313
Denominator:
Denominator for basic income (loss) per share (in shares)									60,116,530	58,292,633	56,736,009
Add effect of dilutive securities:
Stock options and equivalents										2,463,000	808,000
Convertible debt										5,551,000
Denominator for diluted net income (loss) per share: (in shares)									60,116,530	66,307,364	57,543,979
Diluted net income (loss) per share (in dollars per share)	$ (0.51)	$ (0.20)	$ (0.36)	$ (0.20)	$ 1.23	$ 0.11	$ 0.21	$ 0.30	$ (1.26)	$ 2.05	$ 0.75
Total number of antidilutive outstanding common stock options excluded from the diluted net income per common share computation (in shares)									19,421,000	1,578,000	4,824,000
Convertible debt
Add effect of dilutive securities:
Total number of antidilutive outstanding common stock options excluded from the diluted net income per common share computation (in shares)									17,931,000
Stock options and equivalents
Add effect of dilutive securities:
Total number of antidilutive outstanding common stock options excluded from the diluted net income per common share computation (in shares)									1,490,000	1,578,000	4,824,000