Goodwill and Intangible Assets - Additional Information (Detail) $ in Thousands			3 Months Ended	12 Months Ended
	Nov. 30, 2019	Apr. 11, 2018	Dec. 31, 2017 USD ($) Fund	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
Indefinite-lived Intangible Assets [Line Items]
Intangible asset related to its customary advisory agreement				$ 603,294	$ 603,209
Questrade ETFs [Member]
Indefinite-lived Intangible Assets [Line Items]
Intangible asset related to its customary advisory agreement				2,047	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			$ 0	$ 601,247	$ 601,247
Weighted average cost of capital percentage	10.00%	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%	3.00%
Acquisition Of Etfs Business [Member] | Maximum [Member]
Indefinite-lived Intangible Assets [Line Items]
Revenue growth multiple	9.00%	4.00%
Acquisition Of Etfs Business [Member] | Weighted Average [Member]
Indefinite-lived Intangible Assets [Line Items]
Revenue growth multiple	3.40%