XML 74 R71.htm IDEA: XBRL DOCUMENT
v3.19.3

Securities Held-to-Maturity - Additional Information (Detail) - Securities | 9 Months Ended | 12 Months Ended
--- | --- | ---
Sep. 30, 2019 | Dec. 31, 2018
Investments, Debt and Equity Securities [Abstract] |  |
Number of securities determined to be other than temporarily impaired | 0 | 0

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

X
- Definition Number of securities determined to be other than temporarily impaired. + References No definition available. + Details
Name: | wetf_NumberOfSecuritiesDeterminedToBeOtherThanTemporarilyImpaired
Namespace Prefix: | wetf_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration