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Business Combination - Summary of Fair Value of Intangible Assets (Parenthetical) (Detail) - Acquisition of ETFS Business [Member] | Apr. 11, 2018
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Business Acquisition [Line Items] |
Weighted average cost of capital percentage | 11.60%
Minimum [Member] |
Business Acquisition [Line Items] |
Revenue growth percentage | 3.00%
Maximum [Member] |
Business Acquisition [Line Items] |
Revenue growth percentage | 4.00%

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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
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Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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- Definition Estimated weighted average cost of capital. + References No definition available. + Details
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Namespace Prefix: | wetf_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

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- Definition Percentage Of Revenue Growth + References No definition available. + Details
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Namespace Prefix: | wetf_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

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- Details
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Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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- Details
Name: | srt_RangeAxis=srt_MinimumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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- Details
Name: | srt_RangeAxis=srt_MaximumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |