Net Income Per Share - Basic and Diluted EPS (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Numerator:
Net income attributable to Innoviva stockholders, basic	$ 33,790	$ 29,581
Add: interest expense on 2023 Notes	1,415	1,412
Net income attributable to Innoviva stockholders, diluted	$ 35,205	$ 30,993
Denominator:
Weighted-average shares used to compute basic net income per share attributable to Innoviva stockholders	101,059	100,604
Dilutive effect of 2023 Notes	12,189	12,189
Dilutive effect of options and awards granted under equity incentive plan and employee stock purchase plan	128	773
Weighted-average shares used to compute diluted net income per share attributable to Innoviva stockholders	113,376	113,566
Net income per share attributable to Innoviva stockholders
Basic net income per share	$ 0.33	$ 0.29
Diluted net income per share	$ 0.31	$ 0.27
Convertible senior notes | 2025 Notes
Net Income Per Share
Dilutive effect of 2025 Notes	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