Net Income Per Share - Basic and Diluted EPS (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Numerator:
Net income attributable to Innoviva stockholders, basic	$ 72,438	$ 28,218	$ 255,509	$ 170,499
Add: interest expense on 2023 Notes	1,186	1,171	3,553	3,535
Net income attributable to Innoviva stockholders, diluted	$ 73,624	$ 29,389	$ 259,062	$ 174,034
Denominator:
Weighted-average shares used to compute basic net income per share attributable to Innoviva stockholders	69,458,000	101,358,000	86,298,000	101,306,000
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	52	25	49	48
Weighted-average shares used to compute diluted net income per share attributable to Innoviva stockholders	81,699,000	113,572,000	98,536,000	113,543,000
Net income per share attributable to Innoviva stockholders
Basic net income per share	$ 1.04	$ 0.28	$ 2.96	$ 1.68
Diluted net income per share	$ 0.90	$ 0.26	$ 2.63	$ 1.53
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