SUPPLEMENTARY FINANCIAL DATA (UNAUDITED) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
SUPPLEMENTARY FINANCIAL DATA (UNAUDITED)
Total net revenue	$ 75,971	$ 65,755	$ 64,107	$ 55,183	$ 79,858	$ 61,680	$ 67,086	$ 52,380	$ 261,016	$ 261,004	$ 217,217
Operating expenses	2,332	4,962	4,347	3,015	2,638	4,019	4,411	11,685	14,656	22,753	33,613
Income from operations	73,639	60,793	59,760	52,168	77,220	57,661	62,675	40,695	246,360	238,251	183,604
Income tax benefit (expense), net	(12,403)	(10,558)	(10,433)	(8,508)	196,073	0	0	0	(41,902)	196,073	(4)
Net income	57,862	47,051	46,061	40,019	269,215	50,167	56,616	30,330	190,993	406,328	134,272
Net income attributable to noncontrolling interest	11,913	7,242	8,321	6,229	5,455	3,078	1,990	749	33,705	11,272	129
Net income attributable to Innoviva stockholders	$ 45,949	$ 39,809	$ 37,740	$ 33,790	$ 263,760	$ 47,089	$ 54,626	$ 29,581	$ 157,288	$ 395,056	$ 134,143
Basic net income per share	$ 0.45	$ 0.39	$ 0.37	$ 0.33	$ 2.61	$ 0.47	$ 0.54	$ 0.29	$ 1.55	$ 3.92	$ 1.25
Diluted net income per share	$ 0.42	$ 0.36	$ 0.34	$ 0.31	$ 2.34	$ 0.43	$ 0.49	$ 0.27	$ 1.43	$ 3.53	$ 1.17