Sale of Zohydro ER business - Narrative (Details)		12 Months Ended
	Apr. 24, 2015 USD ($)	Dec. 31, 2015 USD ($) employee	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Proceeds from sale of business		$ 82,984,000	$ 89,624,000	$ 0
Net product revenue		0	9,840,000	31,699,000
Stock-based compensation		7,686,000	9,492,000	8,207,000
Zohydro ER [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Proceeds from sale of business	$ 80,000,000
Escrow deposit	$ 10,000,000
Indemnification period	12 months
Consideration received, common stock	$ 10,614,000
Favorable purchase terms		2,425,000
Potential cash receipts based on achievement of milestones	283,500,000
Potential regulatory milestone payments	12,500,000
Potential sale milestone payments	271,000,000
Purchase discounts	2,425,000
Net gain on sale of business	75,424,000
Other income		$ 5,077,000	8,500,000	0
Number of employees effected | employee		116
Modification expense		$ 160,000
Zohydro ER [Member] | Regulatory Exclusivity Rights [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Other income		5,000,000	5,000,000
Zohydro ER [Member] | Carncinogenicity Data [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Other income			3,500,000
Ferrimill Limited [Member] | Zohydro ER [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Net product revenue	926,000
Indemnification Agreement [Member] | Ferrimill Limited [Member] | Zohydro ER [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Indemnification claims	$ 5,000,000
Discontinued Operations [Member] | Zohydro ER [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Stock-based compensation		745,000	1,956,000	21,000
Amortization		$ 166,000	$ 558,000	$ 2,000