Goodwill and Intangible Assets - Additional Information (Detail) $ in Thousands, $ in Thousands	3 Months Ended
	Dec. 31, 2017 USD ($) Fund	Dec. 31, 2017 CAD ($) Fund	Mar. 31, 2018 USD ($)	Jan. 01, 2016 USD ($)
Indefinite-lived Intangible Assets [Line Items]
Intangible asset related to its customary advisory agreement	$ 12,085		$ 12,029
Questrade ETFs [Member]
Indefinite-lived Intangible Assets [Line Items]
Intangible asset related to its customary advisory agreement	$ 2,132		2,076
Questrade ETFs [Member] | WisdomTree Asset Management Canada, Inc [Member]
Indefinite-lived Intangible Assets [Line Items]
Number of ETF acquired by company | Fund	8	8
Assets under management	$ 77,403	$ 99,108
Acquisition of the right to manage Questrade Wealth Management Inc.'s ETFs	2,132	$ 2,675
GreenHaven Commodity Services, LLC [Member]
Indefinite-lived Intangible Assets [Line Items]
Intangible asset related to its customary advisory agreement	$ 9,953		$ 9,953	$ 9,953