Fair value of financial instruments Additional Information (Details) - USD ($)	3 Months Ended		6 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Sep. 30, 2019	Aug. 31, 2019	Jun. 30, 2019
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Realized gain (loss) on non-marketable equity securities			$ 62,000
Unrealized gain (loss) on non-marketable equity securities			62,000	$ 1,259,000
Non-marketable equity investments	$ 458,000		458,000				$ 458,000
Income related to proportionate share of equity investment	797,000	$ 0	797,000	$ 0
Non-marketable debt investments	3,500,000		3,500,000				$ 0
inMarket Media, LLC
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity method investment						$ 15,600,000
Income related to proportionate share of equity investment	$ 797,000		$ 797,000
Convertible Note Receivable 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Convertible notes receivable, interest rate	6.50%		6.50%
Convertible Note Receivable 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Convertible notes receivable, interest rate					6.00%
Significant Unobservable Inputs | Convertible Note Receivable
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Non-marketable debt investments	$ 3,500,000		$ 3,500,000
Significant Unobservable Inputs | Convertible Note Receivable 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Non-marketable debt investments	$ 1,500,000		$ 1,500,000
Significant Unobservable Inputs | Convertible Note Receivable 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Non-marketable debt investments					$ 2,000,000.0