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Significant Accounting Policies - Additional Information (Detail) | 9 Months Ended
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Sep. 30, 2018
Accounting Policies [Abstract] |
Cash and cash equivalents maturity period, maximum | 90 days

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- References No definition available. + Details
Name: | us-gaap_AccountingPoliciesAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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- Definition Cash and cash equivalents criteria maturity period. + References No definition available. + Details
Name: | wetf_CashAndCashEquivalentsCriteriaMaturityPeriod
Namespace Prefix: | wetf_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration