SUPPLEMENTARY FINANCIAL DATA (UNAUDITED) (Details) - USD ($) $ / shares in Units, $ 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
SUPPLEMENTARY FINANCIAL DATA (UNAUDITED)
Net revenue	$ 69,520	$ 48,643	$ 58,562	$ 40,492	$ 43,612	$ 33,309	$ 32,472	$ 24,176	$ 217,217	$ 133,569	$ 53,949
Total operating expenses	(3,111)	(8,621)	(10,732)	(11,149)	(5,951)	(5,391)	(6,595)	(6,644)	(33,613)	(24,581)	(22,369)
Income from operations	66,409	40,022	47,830	29,343	37,661	27,918	25,877	17,532	183,604	108,988	31,580
Net income	58,514	23,767	35,146	16,845	$ 25,471	$ 15,033	$ 14,597	$ 4,435	134,272	59,536	(18,760)
Net income attributable to noncontrolling interest	129	0	0	0					129	0	0
Net income attributable to the Innoviva stockholders	$ 58,385	$ 23,767	$ 35,146	$ 16,845					$ 134,143	$ 59,536	$ (18,760)
Basic net income per share	$ 0.55	$ 0.22	$ 0.33	$ 0.16	$ 0.24	$ 0.14	$ 0.13	$ 0.04	$ 1.25	$ 0.54	$ (0.16)
Diluted net income per share	$ 0.50	$ 0.21	$ 0.30	$ 0.15	$ 0.22	$ 0.13	$ 0.13	$ 0.04	$ 1.17	$ 0.53	$ (0.16)