Goodwill and Intangible Assets - Summary of Indefinite-lived Intangible Assets (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2019 USD ($)
Indefinite-lived Intangible Assets [Line Items]
Beginning balance	$ 603,209
Foreign currency translation	85
Ending balance	603,294
Acquisition Of Etfs Business [Member]
Indefinite-lived Intangible Assets [Line Items]
Beginning balance	601,247
Ending balance	601,247
Questrade ETFs [Member]
Indefinite-lived Intangible Assets [Line Items]
Beginning balance	1,962
Foreign currency translation	85
Ending balance	$ 2,047