DEBT - Narrative (Details) - USD ($)	1 Months Ended					3 Months Ended
	Jun. 30, 2017	Apr. 30, 2017	Nov. 30, 2016	Jul. 31, 2016	May 31, 2013	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017	Sep. 30, 2016
Debt Instrument [Line Items]
Accrued interest						$ 7,600,000		$ 6,200,000
Long-term debt						58,476,000
Proceeds from issuance of debt						0	$ 7,500,000
Warrant, term	10 years			10 years	10 years
Number of securities issued by warrants (in shares)	17,500			97,125
Exercise price of warrants (in usd per share)	$ 27.68			$ 20.00	$ 23.64
Fair value of warrants	$ 300,000			$ 1,000,000
Line of credit
Debt Instrument [Line Items]
Maximum borrowing capacity						$ 50,000,000
Maximum borrowing capacity, percentage of accounts receivable						85.00%
Interest rate (not to be less than)						7.00%
Commitment fee percentage						0.50%
Annual administrative fee						$ 100,000
Debt issuance costs									$ 700,000
Line of credit facility, covenant, minimum cash balance						5,000,000
Line of credit facility, covenant, minimum 12 month revenue						123,300,000
Line of credit facility, remaining borrowing capacity						$ 4,900,000
Line of credit | Prime Rate
Debt Instrument [Line Items]
Basis spread on variable rate						3.50%
Term loans
Debt Instrument [Line Items]
Debt instrument, face amount				24,000,000
Proceeds from issuance of debt	$ 5,000,000		$ 5,000,000	$ 19,000,000
Revenue threshold, trailing four quarter revenue			$ 100,000,000
Interest rate, rate reduction		0.50%
Term loan, covenant, line of credit availability threshold (not less than)						$ 3,000,000
Term loan, Covenant, Adjusted EBITDA, Two consecutive quarters (at least)						$ 1,000,000.0
Fixed Interest Rate | Term loans
Debt Instrument [Line Items]
Interest rate (not to be less than)						13.25%
Interest rate, percentage, payable in cash						3.00%
Interest rate, percentage, payable in kind						10.25%
IPO gross proceeds $75.0 million | Term loans
Debt Instrument [Line Items]
Interest rate (not to be less than)						12.75%
Interest rate, percentage, payable in cash						3.00%
Proceeds from issuance of common stock, threshold amount (at least)						$ 75,000,000.0
Interest rate, percentage, payable in kind						9.75%
EBITDA Thresholds Met | Term loans
Debt Instrument [Line Items]
Interest rate, percentage, payable in cash						3.00%
Adjusted EBITDA threshold (greater than)						$ 1,000,000
EBITDA Thresholds Met | Term loans | Minimum
Debt Instrument [Line Items]
Interest rate (not to be less than)						11.25%
Interest rate, percentage, payable in kind						8.25%
Convertible Promissory Notes
Debt Instrument [Line Items]
Accrued interest on convertible promissory notes							$ 1,246,000
Convertible Promissory Notes | Convertible Promissory Notes
Debt Instrument [Line Items]
Debt instrument, face amount						$ 50,700,000