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Goodwill and Intangible Assets - Summary of Indefinite-lived Intangible Asset (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2017 USD ($)
Indefinite-lived Intangible Assets [Line Items]
Beginning balance	$ 9,953
Increases	2,132
Decreases	0
Ending balance	12,085
GreenHaven Commodity Services, LLC [Member]
Indefinite-lived Intangible Assets [Line Items]
Beginning balance	9,953
Decreases	0
Ending balance	9,953
Questrade ETFs [Member]
Indefinite-lived Intangible Assets [Line Items]
Increases	2,132
Decreases	0
Ending balance	$ 2,132

X

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

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- Definition

Amount of assets, excluding financial assets and goodwill, lacking physical substance and having a projected indefinite period of benefit.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 30
-Section 50
-Paragraph 2
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=66006027&loc=d3e16323-109275

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- Definition

Amount of divestiture of an asset lacking physical substance and having a projected indefinite period of benefit to fair value. Excludes financial assets and goodwill.

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- Definition

Amount of increase in assets, excluding financial assets and goodwill, lacking physical substance with an indefinite life, from an acquisition.

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