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Divestitures - Additional Information (Detail) - USD ($) $ in Millions				3 Months Ended
	Aug. 31, 2020	Apr. 30, 2020	Feb. 14, 2020	Sep. 30, 2021	Jun. 30, 2020	Mar. 31, 2020
Restructuring Cost And Reserve [Line Items]
Purchase price of asset sell	$ 20.0	$ 3.3
Purchase price of agreement			$ 12.9
Proceeds from sale of business			10.0
QuinStreet Brasil Online Marketing e Midia Ltda ("QSB") and VEMM, LLC ("VEMM") [Member] | Euro-Demand Do Brasil Servios de Gerao de Leads Ltda (EDB) [Member]
Restructuring Cost And Reserve [Line Items]
Proceeds from sale of business						$ 1.1
Secured Promissory Note [Member]
Restructuring Cost And Reserve [Line Items]
Secured promissory note, receivable			$ 2.9
Other Income (Expense) [Member]
Restructuring Cost And Reserve [Line Items]
Gain (loss) on disposition of operation				$ 16.6	$ 2.8	$ 12.0

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