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, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Numerator:
Net income attributable to Innoviva stockholders, basic	$ 54,626	$ 35,146	$ 84,207	$ 51,991
Add: interest expense on 2023 Notes	1,417	1,414	2,829	2,821
Net income attributable to Innoviva stockholders, diluted	$ 56,043	$ 36,560	$ 87,036	$ 54,812
Denominator:
Weighted-average shares used to compute basic net income per share attributable to Innoviva stockholders	100,873	107,614	100,739	107,468
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	337	660	555	660
Weighted-average shares used to compute diluted net income per share attributable to Innoviva stockholders	113,399	120,463	113,483	120,317
Net income per share attributable to Innoviva stockholders
Basic net income per share	$ 0.54	$ 0.33	$ 0.84	$ 0.48
Diluted net income per share	$ 0.49	$ 0.30	$ 0.77	$ 0.46
Convertible senior notes \| 2025 Notes
Net income (loss) per share
Dilutive effect of 2025 Notes	0		0
Convertible senior notes \| 2025 Notes \| Common Stock
Net income (loss) per share
Conversion price of convertible notes into common stock (in dollars per share)	$ 17.26		$ 17.26

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