NOVAQUEST FUNDING ARRANGEMENT - Narrative (Details)		9 Months Ended
	Sep. 03, 2019 USD ($)	Sep. 30, 2019 USD ($) $ / shares shares	Dec. 31, 2018	Sep. 30, 2018 USD ($)
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Monthly distribution amount as percent of invoiced R&D		67.00%
Potential milestone payments		$ 37,500,000
Potential milestone payments due upon approval		20,000,000.0
Termination amount		$ 25,000,000.0
Commitment funding amount	$ 5,600,000
NovaQuest
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Commitment amount				$ 25,000,000.0
Stock issuable upon warrants (in shares) | shares		241,225
Exercise price (in usd per share) | $ / shares		$ 10.36
Minimum
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Termination amount, interest rate		8.00%
Maximum
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Termination amount, interest rate		12.00%
Expected volatility
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Warrants, measurement input		0.8556	0.3000
Risk free interest rate
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Warrants, measurement input		0.0150	0.0259
Expected term (in years)
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Warrants, measurement input		10	7.1
Expected dividend yield
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Warrants, measurement input		0.0000	0
NovaQuest Warrants
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Commitment funding amount	$ 900,000