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Commitments and Contingencies - Additional Information (Detail) - USD ($) $ in Thousands | 3 Months Ended
--- | ---
Mar. 31, 2016 | Mar. 31, 2015
Commitments and Contingencies Disclosure [Abstract] |  |
Operating leases expenses | $ 864 | $ 794
Stand by letter of credit decreased | $ 1,384 |

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

X
- Definition Amount of rent expense incurred for leased assets, including but not limited to, furniture and equipment, that is not directly or indirectly associated with the manufacture, sale or creation of a product or product line. + References No definition available. + Details
Name: | us-gaap_LeaseAndRentalExpense
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Letters of credit decreased amount. + References No definition available. + Details
Name: | wetf_LettersOfCreditDecreasedAmount
Namespace Prefix: | wetf_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration