Significant Accounting Policies - Additional Information (Detail) $ in Thousands	12 Months Ended
Dec. 31, 2017 USD ($)
Summary Of Significant Accounting Policies [Line Items]
Cash and cash equivalents maturity period, maximum	90 days
ASU 2016-09 [Member]
Summary Of Significant Accounting Policies [Line Items]
Income tax expense	$ 1,035

Income tax expense associated with stock compensation shortfalls.

No definition available.

Name:	wetf_IncomeTaxExpenseAssociatedWithStockCompensationShortfalls
Namespace Prefix:	wetf_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration