REVENUE - Schedule of Disaggregated Revenue from Contracts with Customers (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Disaggregation of Revenue [Line Items]
Total revenues	$ 77,493	$ 95,413	$ 269,171	$ 286,317
Product sales, net
Disaggregation of Revenue [Line Items]
Total revenues	29,435	95,204	100,627	285,721
Total neurology product sales, net
Disaggregation of Revenue [Line Items]
Total revenues	29,436	32,499	81,317	93,925
Gralise
Disaggregation of Revenue [Line Items]
Total revenues	14,630	21,103	43,272	57,777
CAMBIA
Disaggregation of Revenue [Line Items]
Total revenues	10,365	8,164	24,870	23,862
Zipsor
Disaggregation of Revenue [Line Items]
Total revenues	4,441	3,232	13,175	12,286
NUCYNTA products
Disaggregation of Revenue [Line Items]
Total revenues	11	58,665	18,782	183,299
Lazanda
Disaggregation of Revenue [Line Items]
Total revenues	(12)	4,040	528	13,239
Pharmacy benefit manager dispute reserve
Disaggregation of Revenue [Line Items]
Total revenues	0	0	0	(4,742)
Commercialization rights and facilitation services
Disaggregation of Revenue [Line Items]
Total revenues	27,781	0	87,055	0
Revenue from transfer of inventory
Disaggregation of Revenue [Line Items]
Total revenues	0	0	55,705	0
Royalties and milestone revenue
Disaggregation of Revenue [Line Items]
Total revenues	$ 20,277	$ 209	$ 25,784	$ 596