Net Income Per Share - Basic and Diluted EPS (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Numerator:
Net income attributable to Innoviva stockholders, basic	$ 28,218	$ 39,809	$ 170,499	$ 111,339
Add: interest expense on 2023 Notes	1,171	1,157	3,535	3,482
Net income attributable to Innoviva stockholders, diluted	$ 29,389	$ 40,966	$ 174,034	$ 114,821
Denominator:
Weighted-average shares used to compute basic net income per share attributable to Innoviva stockholders	101,358,000	101,191,000	101,306,000	101,134,000
Dilutive effect of 2023 Notes	12,189,000	12,189,000	12,189,000	12,189,000
Dilutive effect of options and awards granted under equity incentive plan and employee stock purchase plan	25,000	35,000	48,000	71,000
Weighted-average shares used to compute diluted net income per share attributable to Innoviva stockholders	113,572,000	113,415,000	113,543,000	113,394,000
Net income per share attributable to Innoviva stockholders
Basic net income per share	$ 0.28	$ 0.39	$ 1.68	$ 1.10
Diluted net income per share	$ 0.26	$ 0.36	$ 1.53	$ 1.01
Convertible senior notes | 2025 Notes
Net Income Per Share
Dilutive effect of the assumed conversion premium	0	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	$ 17.26	$ 17.26	$ 17.26