Summary of business and significant accounting policies - Advertising Expense (Details) - USD ($)	12 Months Ended
Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Advertising expense	$ 0	$ 334,000	$ 131,000

Amount charged to advertising expense for the period, which are expenses incurred with the objective of increasing revenue for a specified brand, product or product line.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 720
-SubTopic 35
-Section 50
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=6420018&loc=d3e36677-107848

Name:	us-gaap_AdvertisingExpense
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration