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, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Numerator:
Net income attributable to Innoviva stockholders, basic	$ 37,740	$ 54,626	$ 71,530	$ 84,207
Add: interest expense on 2023 Notes	1,158	1,417	2,325	2,829
Net income attributable to Innoviva stockholders, diluted	$ 38,898	$ 56,043	$ 73,855	$ 87,036
Denominator:
Weighted-average shares used to compute basic net income per share attributable to Innoviva stockholders	101,151	100,873	101,105	100,739
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	51	337	90	555
Weighted-average shares used to compute diluted net income per share attributable to Innoviva stockholders	113,391	113,399	113,384	113,483
Net income per share attributable to Innoviva stockholders
Basic net income per share	$ 0.37	$ 0.54	$ 0.71	$ 0.84
Diluted net income per share	$ 0.34	$ 0.49	$ 0.65	$ 0.77
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