NET INCOME PER SHARE - Basic and Diluted EPS (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Aug. 07, 2017
Numerator:
Net income attributable to Innoviva stockholders, basic	$ 224,402	$ 157,288	$ 395,056
Add: interest expense on 2023 Notes	4,717	4,648	5,661
Net income attributable to Innoviva stockholders, diluted	$ 229,119	$ 161,936	$ 400,717
Denominator:
Weighted-average shares used to compute basic net income per share attributable to Innoviva stockholders	101,320	101,150	100,849
Dilutive effect of 2023 Notes	12,189	12,189	12,189
Dilutive effect of options and awards granted under equity incentive plan and employee stock purchase plan	45	70	370
Weighted-average shares used to compute diluted net income per share attributable to Innoviva stockholders	113,554	113,409	113,408
Net income per share attributable to Innoviva stockholders
Basic net income per share	$ 2.21	$ 1.55	$ 3.92
Diluted net income per share	$ 2.02	$ 1.43	$ 3.53
Convertible senior notes | 2025 Notes
Net Income Per Share
Dilutive effect of the assumed conversion premium	0	0	0
Convertible senior notes | 2025 Notes | Common stock
Net Income Per Share
Conversion price of convertible notes into common stock (in dollars per share)				$ 17.26