NET INCOME (LOSS) PER SHARE (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Basic net income (loss) per share
Net income (loss)	$ (44,368)	$ (12,894)	$ (10,541)	$ (20,917)	$ (30,667)	$ (11,785)	$ (21,653)	$ (11,633)	$ (88,720)	$ (75,738)	$ 131,762
Denominator (in shares)									61,296,875	60,116,530	58,292,633
Basic net income (loss) per share (in dollars per share)	$ (0.72)	$ (0.21)	$ (0.17)	$ (0.34)	$ (0.51)	$ (0.20)	$ (0.36)	$ (0.20)	$ (1.45)	$ (1.26)	$ 2.26
Numerator:
Net income (loss)	$ (44,368)	$ (12,894)	$ (10,541)	$ (20,917)	$ (30,667)	$ (11,785)	$ (21,653)	$ (11,633)	$ (88,720)	$ (75,738)	$ 131,762
Add interest expense on convertible debt, net of tax											4,256
Net income (loss), diluted									$ (88,720)	$ (75,738)	$ 136,018
Denominator (in shares)									61,296,875	60,116,530	58,292,633
Add effect of dilutive securities:
Stock options and equivalents											2,463
Convertible debt											5,551
Denominator for diluted loss per share: (in shares)									61,296,875	60,116,530	66,307,364
Diluted net income (loss) per share (in dollars per share)	$ (0.72)	$ (0.21)	$ (0.17)	$ (0.34)	$ (0.51)	$ (0.20)	$ (0.36)	$ (0.20)	$ (1.45)	$ (1.26)	$ 2.05
Total potentially dilutive common shares (in shares)									21,302	19,421	1,578
Convertible Notes
Add effect of dilutive securities:
Total potentially dilutive common shares (in shares)									17,931	17,931
Stock options and equivalents
Add effect of dilutive securities:
Total potentially dilutive common shares (in shares)									3,371	1,490	1,578