REVENUE - Schedule of Disaggregated Revenue from Contracts with Customers (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Disaggregation of Revenue [Line Items]
Total revenues	$ 55,147	$ 77,493	$ 170,278	$ 269,171
Product sales, net
Disaggregation of Revenue [Line Items]
Total revenues	27,502	29,435	79,889	100,627
Total neurology product sales, net
Disaggregation of Revenue [Line Items]
Total revenues	26,339	29,436	78,737	81,317
Gralise
Disaggregation of Revenue [Line Items]
Total revenues	14,931	14,630	46,008	43,272
CAMBIA
Disaggregation of Revenue [Line Items]
Total revenues	8,135	10,365	23,701	24,870
Zipsor
Disaggregation of Revenue [Line Items]
Total revenues	3,273	4,441	9,028	13,175
NUCYNTA products
Disaggregation of Revenue [Line Items]
Total revenues	1,254	11	1,153	18,782
Lazanda
Disaggregation of Revenue [Line Items]
Total revenues	(91)	(12)	(1)	528
Commercialization rights and facilitation services, net
Disaggregation of Revenue [Line Items]
Total revenues	27,304	27,781	89,163	87,055
Revenue from transfer of inventory
Disaggregation of Revenue [Line Items]
Total revenues	0	0	0	55,705
Royalties and milestone revenue
Disaggregation of Revenue [Line Items]
Total revenues	$ 341	$ 20,277	$ 1,226	$ 25,784