License and Development Agreements - Endo License and Development Agreement - Additional Information (Detail) $ in Millions	1 Months Ended				9 Months Ended
	Nov. 30, 2015 USD ($)	Oct. 31, 2015 USD ($)	Feb. 28, 2015 USD ($)	May 31, 2012 USD ($)	Sep. 30, 2017 USD ($) Clinical_Trials	Jun. 30, 2014 USD ($)	Jan. 31, 2014 USD ($)	Jan. 31, 2012 USD ($)
Revenue Recognition, Milestone Method [Line Items]
Non-refundable payment received								$ 30
Potential milestone payments on intellectual property rights				$ 15
Potential payments upon filing and acceptance			$ 10
Potential milestone payment receivable upon regulatory approval		$ 50
Milestone payment upon regulatory approval deferred for future revenue recognition	$ 20
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 during the nine months ended September 30, 2017 in the accompanying condensed consolidated statement of operations (see note 7, Business Combination and Asset 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
Clinical Trials Full Enrollment [Member]
Revenue Recognition, Milestone Method [Line Items]
Potential milestone payment received, clinical development					$ 20
Number of clinical trials | Clinical_Trials					2
Clinical Trials One [Member]
Revenue Recognition, Milestone Method [Line Items]
Potential milestone payment received, clinical development							$ 10
Clinical Trials Two [Member]
Revenue Recognition, Milestone Method [Line Items]
Potential milestone payment received, clinical development						$ 10