Fair value of financial instruments - Additional Information (Details) - USD ($)	1 Months Ended	3 Months Ended
	Sep. 30, 2020	Sep. 30, 2020	Sep. 30, 2019	Jul. 31, 2020	Jun. 30, 2020	Jan. 31, 2020	Aug. 16, 2019
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Non-marketable equity investments	$ 8,970,000	$ 8,970,000			$ 6,670,000
Unrealized gain (loss) on non-marketable equity securities		0	$ 0
Income related to proportionate share of equity investment		616,000	$ 0
Non-marketable equity investments accounted for under the equity method	20,557,000	20,557,000			20,027,000
Warrant to purchase non-marketable equity investment units	817,000	817,000			713,000
Non-marketable debt investments	9,007,000	9,007,000			5,917,000
Grab
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Non-marketable equity investments						$ 6,200,000
Equity method investment						6,200,000
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
Investment In Acquired Company
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Non-marketable equity investments	200,000	200,000
Realized gain on non-marketable equity investments	247,000
Investment In Acquired Company | Prepaid Expenses and Other Current Assets
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Non-marketable equity investments	447,000	447,000
Series A-3 Redeemable Convertible Preferred Shares
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Non-marketable equity investments				$ 2,500,000
Convertible Note Receivable
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Non-marketable debt investments	$ 9,000,000.0	$ 9,000,000.0			$ 5,900,000
Convertible Note Receivable 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Convertible notes receivable, interest rate					6.50%
Convertible Note Receivable 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Convertible notes receivable, interest rate					6.00%
Convertible Note Receivable 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Convertible notes receivable, interest rate	6.00%	6.00%
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	$ 7,000,000.0	$ 7,000,000.0		3,000,000.0	4,000,000.0
Significant Unobservable Inputs | Convertible Note Receivable 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Non-marketable debt investments	507,000	507,000		$ 90,000	$ 417,000
Maximum loan amount	$ 710,000	710,000
Warrant
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable equity securities						$ 448,000
Fair value adjustment of warrants		$ 104,000
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