REDEEMABLE CONVERTIBLE PREFERRED STOCK - Narrative (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended	3 Months Ended
	May 31, 2017	Mar. 31, 2018	Jun. 30, 2017	Mar. 31, 2017	Jan. 26, 2018	Dec. 31, 2017	Feb. 28, 2017	Jul. 31, 2016	May 31, 2013
Temporary Equity [Line Items]
Shares authorized (in shares)	96,131,002				25,000,000		82,683,212
Shares authorized (in shares)	83,000,000	100,000,000			100,000,000	83,000,000
Redeemable convertible preferred stock, par value (in usd per share)					$ 0.0001
Issuance costs		$ 1,232		$ 181
Conversion of stock, shares converted (in shares)	801,329
Shares issued (in shares)		20,226,000				3,439,000
Class of warrant, numerator input value (in usd per share)	$ 68.9516
Number of trading days	30 days
Exercise price of warrants (in usd per share)			$ 27.68					$ 20.00	$ 23.64
Series G Stock
Temporary Equity [Line Items]
Shares authorized (in shares)		0				1,385,000
Issuance of Series G and Series G’ Stock	$ 11,900
Issuance of Series G and Series G’ Stock (in shares)	346,334
Redeemable convertible preferred stock, par value (in usd per share)	$ 0.0001	$ 0.0001				$ 0.0001
Shares issued (in usd per share)	$ 34.4758
Issuance costs	$ 100
Shares issued (in shares)	346,334
Class of warrant, numerator input value (in usd per share)	$ 68.9516
Number of trading days	30 days
Number of days following prospectus	180 days
Number of days prior to sale of company	10 days
Exercise price of warrants (in usd per share)	$ 0.0004
Proceeds from issuance of Series G preferred stock	$ 11,900
Redeemable convertible preferred stock, residual value	4,500
Deemed dividend related to beneficial conversion feature	$ 6,100
Deemed dividend related to beneficial conversion feature			$ 4,500
Series G’ Stock
Temporary Equity [Line Items]
Shares authorized (in shares)		0				5,339,000
Redeemable convertible preferred stock, par value (in usd per share)	$ 0.0001	$ 0.0001				$ 0.0001
Shares issued (in usd per share)	$ 2.758
Conversion of stock, shares converted (in shares)	1,295,746
Additional Paid-In Capital | Series G Stock
Temporary Equity [Line Items]
Beneficial conversion feature of Series G stock	$ 4,500