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Organizational and Description of Business- Additional Information (Detail) - USD ($) $ in Thousands | 3 Months Ended | 9 Months Ended
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Sep. 30, 2018 | Sep. 30, 2017 | Sep. 30, 2018 | Sep. 30, 2017
Organization Consolidation And Presentation Of Financial Statements [Line Items] |  |  |  |
Operating income (loss) | $ 21,708 | $ 15,224 | $ 49,460 | $ 43,852
WisdomTree Japan [Member] |  |  |  |
Organization Consolidation And Presentation Of Financial Statements [Line Items] |  |  |  |
Operating income (loss) | $ (1,342) | $ (1,085) | $ (3,698) | $ (3,447)
Acquisition of ETFS Business [Member] |  |  |  |
Organization Consolidation And Presentation Of Financial Statements [Line Items] |  |  |  |
Acquisition completion date |  |  | Apr. 11, 2018 |

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