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Goodwill and Intangible Assets - Additional Information (Detail) $ in Thousands		3 Months Ended		6 Months Ended
	Apr. 11, 2018	Jun. 30, 2019 USD ($)	Dec. 31, 2017 Fund	Jun. 30, 2019 USD ($)	Dec. 31, 2018 USD ($)
Indefinite-lived Intangible Assets [Line Items]
Intangible asset related to its customary advisory agreement		$ 603,291		$ 603,291	$ 603,209
Impairment Losses Attributable To Goodwill		0
Questrade ETFs [Member]
Indefinite-lived Intangible Assets [Line Items]
Intangible asset related to its customary advisory agreement		2,044		2,044	1,962
Questrade ETFs [Member] | WisdomTree Asset Management Canada, Inc [Member]
Indefinite-lived Intangible Assets [Line Items]
Number of ETF acquired by company | Fund			8
Acquisition Of Etfs Business [Member]
Indefinite-lived Intangible Assets [Line Items]
Intangible asset related to its customary advisory agreement		$ 601,247		$ 601,247	$ 601,247
Weighted average cost of capital percentage	11.60%
Acquisition completion date				Apr. 11, 2018
Acquisition Of Etfs Business [Member] | Minimum [Member]
Indefinite-lived Intangible Assets [Line Items]
Revenue growth multiple	3.00%
Acquisition Of Etfs Business [Member] | Maximum [Member]
Indefinite-lived Intangible Assets [Line Items]
Revenue growth multiple	4.00%

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Date when the acquirer obtains control of the acquiree, in CCYY-MM-DD format.

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