NET LOSS PER SHARE (Tables)

12 Months Ended

Dec. 31, 2017

Earnings Per Share [Abstract]

Schedule of Basic and Diluted Net Loss Per Share

The following table presents the calculation of basic and diluted net loss per share (in thousands, except per share data):

	Year Ended December 31,
	2017			2016			2015
Net loss	$	(62,813	)	$	(171,590	)	$	(179,817	)
Deemed dividend on Series E preferred stock	—			—			(32,200		)
Net loss attributable to common stockholders	$	(62,813	)	$	(171,590	)	$	(212,017	)
Basic shares:
Weighted-average common shares outstanding	380,921			344,393			175,139
Weighted-average unvested shares	(1,577		)	(2,838		)	(4,641		)
Weighted-average shares used to compute basic net loss per share	379,344			341,555			170,498
Diluted shares:
Weighted-average shares used to compute diluted net loss per share	379,344			341,555			170,498
Loss per share attributable to common stockholders:
Basic	$	(0.17	)	$	(0.50	)	$	(1.24	)
Diluted	$	(0.17	)	$	(0.50	)	$	(1.24	)

Schedule of Antidilutive Securities Excluded from Calculation of Diluted Net Loss Per Share

The following potential common shares were excluded from the calculation of diluted net loss per share attributable to common stockholders because their effect would have been anti-dilutive for the periods presented (in thousands):

	Year Ended December 31,
	2017	2016	2015
Stock options and restricted stock units	68,588	88,705	111,148
Common stock warrants	19,173	9,457	9,544
Unvested shares	1,300	1,892	3,420
Employee stock purchase plan	157	216	172
Total anti-dilutive securities	89,218	100,270	124,284