License and Development Agreements - Endo License and Development Agreement - Additional Information (Detail) - USD ($)	1 Months Ended	12 Months Ended
	Nov. 30, 2015	Dec. 31, 2018	Oct. 31, 2015
Revenue Recognition, Milestone Method [Line Items]
Potential milestone payment receivable upon regulatory approval			$ 50,000,000
Milestone payment upon regulatory approval deferred for future revenue recognition	$ 20,000,000
Patent extension starting period		2020
Patent extension ending period		2027
Royalty payment description		$50 million upon regulatory approval, earned in October 2015 and received in November 2015. Of the $50 million received in November 2015, $20 million related to a patent extension and was recorded as deferred revenue because all or a portion of such $20 million was contingently refundable to Endo if a third party generic product was introduced in the U.S. during the patent extension period from 2020 to 2027. However, due to the Company and Endo entering into a Termination Agreement on December 7, 2016 which terminated the BELBUCA license to Endo effective January 6, 2017, the deferred $20 million was recognized as revenue in January 2017. (See note 8, Business Combinations and BELBUCA Acquisition).
Endo Agreement [Member]
Revenue Recognition, Milestone Method [Line Items]
Deferred revenue refund payment		$ 20
Termination agreement date		Dec. 07, 2016
License termination effective date		Jan. 06, 2017