Nature of Operations, Risks and Uncertainties and Liquidity - Additional Information (Detail) - USD ($)		1 Months Ended	3 Months Ended								12 Months Ended
	Oct. 26, 2015	Oct. 31, 2015	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Jul. 01, 2015	Apr. 06, 2015	Jan. 06, 2015	Nov. 04, 2014	Aug. 20, 2014	Dec. 31, 2012
Debt Instrument [Line Items]
Accumulated deficit			$ (554,520,000)				$ (514,139,000)				$ (554,520,000)	$ (514,139,000)
Net loss from operation			(4,196,000)	$ (4,668,000)	$ (4,564,000)	$ (4,668,000)	(3,301,000)	$ (2,120,000)	$ (1,539,000)	$ (2,345,000)	(18,096,000)	(9,305,000)	$ (7,604,000)
Net loss			(10,127,000)	$ (4,422,000)	$ 7,136,000	$ (32,968,000)	420,000	$ (14,373,000)	$ (8,069,000)	$ (3,358,000)	(40,381,000)	(25,380,000)	(20,939,000)
Net cash provided (outlays) from operation and capital expenditures											(2,800,000)	(8,400,000)	3,100,000
Net cash provided (outlays) include receipts of deferred revenue											14,600,000	0	10,000,000
Stockholder ' deficit			(151,918,000)				(111,950,000)				(151,918,000)	(111,950,000)	(86,801,000)						$ (66,066,000)
Cash			12,898,000				3,683,000				12,898,000	3,683,000	$ 4,053,000						$ 1,484,000
Company's financial obligations under Reimbursement Notes			$ 61,172,000				44,546,000				$ 61,172,000	44,546,000
Maximum borrowing capacity																		$ 20,000,000
Loan interest rate			13.00%								13.00%
Payment received from Novo Nordisk	$ 14,000,000	$ 14,000,000
Percent of extraordinary receipts used to pre-pay certain loans and notes	50.00%
Loans and notes, current			$ 7,000,000								$ 7,000,000
Maximum [Member]
Debt Instrument [Line Items]
Waiver period on certain loans and notes											1 year
Expansion License Agreement [Member]
Debt Instrument [Line Items]
Payment received from Novo Nordisk	$ 5,000,000
GLP-1 License Agreement [Member]
Debt Instrument [Line Items]
Payment received from Novo Nordisk	$ 9,000,000
Loan Agreement [Member]
Debt Instrument [Line Items]
Company's financial obligations under Loan Agreement			22,800,000								$ 22,800,000
Company's financial obligations under Reimbursement Notes			22,801,000				$ 8,307,000				22,801,000	$ 8,307,000
Maximum borrowing capacity			20,000,000								$ 20,000,000
Maturity date of loans											Dec. 31, 2019
Principal amount			$ 22,800,000								$ 22,800,000			$ 2,000,000	$ 5,000,000	$ 5,000,000	$ 3,000,000	$ 5,000,000
Reimbursement Notes [Member]
Debt Instrument [Line Items]
Maturity date of loans											Mar. 31, 2022
Loan interest rate			10.00%								10.00%
Principal amount			$ 800,000								$ 800,000
Second Amended and Restated [Member]
Debt Instrument [Line Items]
Company's financial obligations under Convertible Notes			46,500,000								46,500,000
Company's financial obligations under Bridge Notes			2,100,000								2,100,000
Second Amended and Restated [Member] | Reimbursement Notes [Member]
Debt Instrument [Line Items]
Company's financial obligations under Reimbursement Notes			$ 800,000								$ 800,000