REVENUE - Schedule of Disaggregated Revenue from Contracts with Customers (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Disaggregation of Revenue [Line Items]
Total revenues	$ 57,929	$ 128,404
Product sales, net
Disaggregation of Revenue [Line Items]
Total revenues	26,450	44,354
Total neurology product sales, net
Disaggregation of Revenue [Line Items]
Total revenues	26,317	25,989
Gralise
Disaggregation of Revenue [Line Items]
Total revenues	13,278	14,827
CAMBIA
Disaggregation of Revenue [Line Items]
Total revenues	8,808	6,416
Zipsor
Disaggregation of Revenue [Line Items]
Total revenues	4,231	4,746
NUCYNTA products
Disaggregation of Revenue [Line Items]
Total revenues	62	18,145
Lazanda
Disaggregation of Revenue [Line Items]
Total revenues	71	220
Commercialization rights and facilitation services
Disaggregation of Revenue [Line Items]
Total revenues	30,856	28,095
Revenue from transfer of inventory
Disaggregation of Revenue [Line Items]
Total revenues	0	55,705
Royalties and milestone revenue
Disaggregation of Revenue [Line Items]
Total revenues	$ 623	$ 250