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Goodwill and Intangible Assets - Summary of Indefinite-lived Intangible Assets (Detail) $ in Thousands	6 Months Ended
	Jun. 30, 2018 USD ($)
Indefinite-lived Intangible Assets [Line Items]
Beginning balance	$ 12,085
Foreign currency translation	(105)
Other increases/(decreases)	601,247
Ending balance	613,227
Acquisition of ETFS Business [Member]
Indefinite-lived Intangible Assets [Line Items]
Other increases/(decreases)	601,247
Ending balance	601,247
GreenHaven Commodity Services, LLC [Member]
Indefinite-lived Intangible Assets [Line Items]
Beginning balance	9,953
Ending balance	9,953
Questrade ETFs [Member]
Indefinite-lived Intangible Assets [Line Items]
Beginning balance	2,132
Foreign currency translation	(105)
Ending balance	$ 2,027

X

- Definition

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+ 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://fasb.org/us-gaap/role/ref/legacyRef
-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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Amount of foreign currency translation gain (loss) which increases (decreases) an asset, excluding financial assets and goodwill, lacking physical substance and having a projected indefinite period of benefit to fair value.

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Amount of increase (decrease) of assets, excluding financial assets and goodwill, lacking physical substance and having a projected indefinite period of benefit, from foreign currency translation and purchase accounting adjustments.

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