ORGANIZATION AND NATURE OF BUSINESS; BASIS OF PRESENTATION; PRINCIPLES OF CONSOLIDATION (Details)						1 Months Ended				12 Months Ended
	Jan. 23, 2024 shares	Jul. 11, 2023	Jun. 09, 2023 USD ($) shares	Apr. 21, 2023 USD ($)	Mar. 13, 2023	Jan. 31, 2024 USD ($) shares	Mar. 31, 2023	Aug. 31, 2022 USD ($)	Sep. 30, 2021 shares	Dec. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)	Jun. 30, 2023 USD ($)	Mar. 31, 2022 USD ($)	Mar. 31, 2018 USD ($)
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Reverse stock split ratio		0.1
Accumulated deficit										$ 668,857,000	$ 607,239,000
Net loss										61,618,000	62,493,000	$ 77,702,000
Net cash used in operating activities										40,196,000	48,728,000	47,323,000
Working capital										12,400,000
Debt Instrument [Line Items]
2.50% Notes extinguished in connection with exchange transaction										0	49,624,000	$ 0
Accrued interest, related-party										0	663,000
Net proceeds										13,600,000
Cash and cash equivalents and investments										13,200,000	$ 45,600,000
Decrease in cash and cash equivalents and investments										$ 32,400,000
Restructuring Support Agreement | Related Party | Series A Preferred Stock
Debt Instrument [Line Items]
Conversion of stock, shares converted (in shares) | shares			400,000
Jack W. Schuler Living Trust | Affiliated Entity | Series A Preferred Stock
Debt Instrument [Line Items]
Conversion of stock, shares converted (in shares) | shares									4,000,000
Outstanding notes | Lender | Ad Hoc Noteholder Group
Debt Instrument [Line Items]
Risk concentration (as a percent)					85.00%		85.00%
March 2022 Securities Purchase Agreement | Jack W. Schuler Living Trust | Affiliated Entity
Debt Instrument [Line Items]
Sale of stock (in shares) | shares			500,000
Restructuring Support Agreement | Jack W. Schuler Living Trust | Affiliated Entity
Debt Instrument [Line Items]
Aggregate purchase price			$ 10,000,000
Public offering backstop			10,000,000										$ 10,000,000
Restructuring Support Agreement | Jack W. Schuler Living Trust | Affiliated Entity | Common Shares
Debt Instrument [Line Items]
Aggregate purchase price													10,000,000
Private Placement | March 2022 Securities Purchase Agreement | Jack W. Schuler Living Trust | Affiliated Entity
Debt Instrument [Line Items]
Net proceeds			4,000,000
Aggregate purchase price														$ 4,000,000
Subsequent Event | Public and Private Placement Offerings
Debt Instrument [Line Items]
Sale of stock (in shares) | shares						8,100,000
Net proceeds						$ 12,300,000
Subsequent Event | Public and Private Placement Offerings | Common Shares
Debt Instrument [Line Items]
New issues per offering unit (in shares) | shares						1
Number of securities called by each warrants (in shares) | shares						1
Subsequent Event | Public and Private Placement Offerings | Shares issuable upon the exercise of the Warrant
Debt Instrument [Line Items]
New issues per offering unit (in shares) | shares						1
Subsequent Event | Private Placement | Schuler Purchase Obligation | Jack W. Schuler Living Trust
Debt Instrument [Line Items]
Sale of stock (in shares) | shares	1,200,000
2.50% Convertible Notes due 2023 | Convertible Notes
Debt Instrument [Line Items]
Interest rate					2.50%										2.50%
Accrued interest, related-party			1,000,000
Aggregate principal amount													$ 10,000,000		$ 150,000,000
2.50% Convertible Notes due 2023 | Convertible Notes | Restructuring Support Agreement
Debt Instrument [Line Items]
Aggregate principal amount exchanged			55,900,000
Accrued interest, related-party			$ 1,000,000
2.50% Convertible Notes due 2023 | Convertible Notes | August 2022 Exchange Transaction | Jack W. Schuler Living Trust
Debt Instrument [Line Items]
Aggregate principal amount exchanged								$ 49,900,000
5.00% Convertible Notes Due 2026 | Convertible Notes
Debt Instrument [Line Items]
Interest rate			5.00%										5.00%
5.00% Convertible Notes Due 2026 | Convertible Notes | Restructuring Support Agreement
Debt Instrument [Line Items]
2.50% Notes extinguished in connection with exchange transaction			$ 56,900,000
Aggregate principal amount			$ 10,000,000
Restructuring Support Agreement | Senior Notes | Affiliated Entity
Debt Instrument [Line Items]
Shares issued (in shares) | shares			3,400,000
Five Point Zero Percent Secured Promissory Note | Senior Notes | Jack W. Schuler Living Trust | Affiliated Entity
Debt Instrument [Line Items]
2.50% Notes extinguished in connection with exchange transaction			$ 25,400,000
Shares issued (in shares) | shares			3,400,000
Five Point Zero Percent Secured Promissory Note | Senior Notes | Jack W. Schuler Living Trust | August 2022 Exchange Transaction | Affiliated Entity
Debt Instrument [Line Items]
Aggregate principal amount exchanged				$ 34,900,000				$ 34,900,000