Fair value of financial instruments - Additional Information (Details) - USD ($)	3 Months Ended		9 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2020	Mar. 31, 2019	Jan. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Aug. 31, 2019	Aug. 16, 2019	Jun. 30, 2019
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable equity securities										$ 1,349,000
Unrealized gain (loss) on non-marketable equity securities			$ 0	$ 1,260,000
Non-marketable equity investments	$ 6,670,000		6,670,000							458,000
Income related to proportionate share of equity investment	(103,000)	$ 0	694,000	$ 0
Non-marketable debt investments	$ 5,500,000		$ 5,500,000							0
Grab
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity method investment					$ 6,200,000
inMarket Media, LLC
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity method investment								$ 19,800,000
Series B Preferred Stock Units and Warrants
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity method investment					4,000,000.0
Preferred Units
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity method investment					3,600,000
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
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable equity securities										$ 0
Significant Unobservable Inputs | Convertible Note Receivable
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Non-marketable debt investments	$ 5,500,000		$ 5,500,000
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
Significant Unobservable Inputs | Convertible Note Receivable 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Non-marketable debt investments	4,000,000.0		4,000,000.0				$ 2,000,000.0
Additional convertible note receivable	2,000,000.0
Warrant
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable equity securities	$ 448,000		$ 448,000		$ 448,000
Discontinued Operations, Disposed of by Sale | Ads Business
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Member interest value								$ 15,600,000	$ 15,600,000