ORGANIZATION AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - REVENUES (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Revenues
Total product sales, net	$ 94,159	$ 95,204	$ 100,232	$ 90,285	$ 123,675	$ 110,303	$ 116,517	$ 104,571	$ 379,880	$ 455,066	$ 341,750
Royalty revenue									844	831	985
Total revenues	$ 94,407	$ 95,413	$ 100,457	$ 90,447	$ 123,911	$ 110,524	$ 116,682	$ 104,780	380,724	455,897	342,735
NUCYNTA products
Revenues
Product sales, gross									239,539	281,261	189,854
Gralise
Revenues
Product sales, gross									77,034	88,446	81,054
CAMBIA
Revenues
Product sales, gross									31,597	31,273	27,426
Lazanda
Revenues
Product sales, gross									15,010	26,547	17,711
Zipsor
Revenues
Product sales, gross									$ 16,700	$ 27,539	$ 25,705