Net Income Per Share - Basic and Diluted EPS (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Numerator:
Net income attributable to Innoviva stockholders, basic	$ 88,948	$ 76,844	$ 183,071	$ 142,281
Add: interest expense on 2023 Notes	1,163	1,184	2,367	2,364
Net income attributable to Innoviva stockholders, diluted	$ 90,111	$ 78,028	$ 185,438	$ 144,645
Denominator:
Weighted-average shares used to compute basic net income per share attributable to Innoviva stockholders	88,423	101,324	94,858	101,280
Dilutive effect of 2023 Notes	12,189	12,189	12,189	12,189
Dilutive effect of options and awards granted under equity incentive plan and employee stock purchase plan	27	32	49	58
Weighted-average shares used to compute diluted net income per share attributable to Innoviva stockholders	100,639	113,545	107,096	113,527
Net income per share attributable to Innoviva stockholders
Basic net income per share	$ 1.01	$ 0.76	$ 1.93	$ 1.40
Diluted net income per share	$ 0.90	$ 0.69	$ 1.73	$ 1.27
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