LONG-TERM OBLIGATIONS - Additional Information (Detail)	9 Months Ended	12 Months Ended
	Sep. 30, 2015 USD ($)	Dec. 31, 2012 USD ($) ft²	Nov. 06, 2015 ft²	Dec. 31, 2014 USD ($)
Debt Disclosure [Line Items]
Rentable square feet of office and laboratory facilities | ft²		45,000
Lease agreement term		10 years
Aggregate minimum lease commitment over payment lease term		$ 15,000,000
Letter of credit given to landlord to secure lease obligation		1,100,000
Proceed from unsecured loan		671,000
Principal amount of Loan	$ 484,000			$ 527,000
Capitalized leasehold improvements	4,554,000			$ 4,554,000
Maximum
Debt Disclosure [Line Items]
Tenant improvement allowance		$ 2,600,000
Extended Term
Debt Disclosure [Line Items]
Lease agreement term		5 years
Burlington Facility
Debt Disclosure [Line Items]
Capitalized leasehold improvements	4,600,000
Healthcare Royalty Partners
Debt Disclosure [Line Items]
Loan principal balance	84,100,000
Debt extinguishment	$ 82,200,000
Healthcare Royalty Partners | LFRP | Tranche A and Tranche B Loans (Original Loan)
Debt Disclosure [Line Items]
Interest on lease	12.00%
Notes Payable | Healthcare Royalty Partners
Debt Disclosure [Line Items]
Interest Expense	$ 1,900,000
Subsequent Event
Debt Disclosure [Line Items]
Rentable square feet of office and laboratory facilities | ft²			20,000