Note 3 - Short-term Financial Instruments (Details Textual) - USD ($) $ in Thousands	12 Months Ended
Jun. 30, 2017	Jun. 30, 2016
Impairment of Financial Assets	$ 0	$ 0

The amount of impairment loss recognized in the period resulting from the write-down of the carrying amount of a financial assets to fair value.

No definition available.

Name:	avir_ImpairmentOfFinancialAssets
Namespace Prefix:	avir_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration