NET INCOME (LOSS) PER SHARE - Schedule of Calculations of Basic and Diluted Net Income per Share and Potential Common Shares (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2017
Numerator:
Net income (loss)	$ 19,211	$ (3,603)	$ (26,428)	$ (62,504)	$ 16,817	$ 89,685	$ (2,468)	$ (24,222)	$ (73,324)	$ 79,812	$ 33,291
Denominator:
Denominator for basic net income per share - weighted average common shares outstanding (in shares)									78,617	87,425	92,226
Dilutive common equivalent shares:
Weighted average restricted stock units (in shares)									0	836	694
Denominator for diluted net income per share - weighted average shares outstanding (in shares)									78,617	88,261	92,920
Net income (loss) per share:
Basic net income (loss) per share (in dollars per share)									$ (0.93)	$ 0.91	$ 0.36
Diluted net income (loss) per share (in dollars per share)	$ 0.24	$ (0.05)	$ (0.34)	$ (0.78)	$ 0.20	$ 1.02	$ (0.03)	$ (0.27)	$ (0.93)	$ 0.90	$ 0.36