REVENUE - Schedule of Disaggregated Revenue from Contracts with Customers (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Disaggregation of Revenue [Line Items]
Total revenues	$ 20,917	$ 57,929
Product sales, net
Disaggregation of Revenue [Line Items]
Total revenues	9,252	26,450
Total neurology product sales, net
Disaggregation of Revenue [Line Items]
Total revenues	9,152	26,317
CAMBIA
Disaggregation of Revenue [Line Items]
Total revenues	6,274	8,808
Zipsor
Disaggregation of Revenue [Line Items]
Total revenues	2,331	4,231
Gralise
Disaggregation of Revenue [Line Items]
Total revenues	547	13,278
NUCYNTA and Lazanda product sales adjustments
Disaggregation of Revenue [Line Items]
Total revenues	100	133
Commercialization agreement, net
Disaggregation of Revenue [Line Items]
Total revenues	11,258	30,856
Royalties and milestone revenue
Disaggregation of Revenue [Line Items]
Total revenues	$ 407	$ 623