Commitments and Contingencies - Additional Information (Detail) - USD ($)	3 Months Ended	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Contingencies And Commitments [Line Items]
Lease expense		$ 300,000	$ 300,000	$ 300,000
Lease term		89 months
CDC [Member]
Contingencies And Commitments [Line Items]
Royalties received		$ 20,000
Granted royalty on sales of the next BEMA product		1.00%
Net sales of next BEMA Product		$ 7,500,000
Minimum [Member] | CDC [Member]
Contingencies And Commitments [Line Items]
Royalties received		$ 375,000
Opioid PMR Consortium [Member]
Contingencies And Commitments [Line Items]
Participation expense	$ 4,300,000