Number of shares of equity interests issued or issuable to acquire entity.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 30
-Section 50
-Paragraph 1
-Subparagraph (b)(4)
-URI http://asc.fasb.org/extlink&oid=35744584&loc=d3e6927-128479

+ Details

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Namespace Prefix:	us-gaap_
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Balance Type:	na
Period Type:	duration

- Definition

This element represents acquisition-related costs incurred to effect a business combination which costs have been expensed during the period. Such costs include finder's fees; advisory, legal, accounting, valuation, and other professional or consulting fees; general administrative costs, including the costs of maintaining an internal acquisitions department; and may include costs of registering and issuing debt and equity securities.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 10
-Section 25
-Paragraph 23
-URI http://asc.fasb.org/extlink&oid=84229725&loc=d3e1043-128460

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Balance Type:	debit
Period Type:	duration

- Definition

Amount of current borrowing capacity under the credit facility considering any current restrictions on the amount that could be borrowed (for example, borrowings may be limited by the amount of current assets), but without considering any amounts currently outstanding under the facility.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.19(b),22(b))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

+ References

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Namespace Prefix:	us-gaap_
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Balance Type:	credit
Period Type:	instant

- Definition

The cash outflow to acquire asset without physical form usually arising from contractual or other legal rights, excluding goodwill.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 13
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=109223946&loc=d3e3213-108585

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Common Stock Shares Issuable Upon Conversion Of Convertible Preferred Stock

+ References

No definition available.

+ Details

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Namespace Prefix:	wetf_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

- Definition

Gain/loss from revaluation of deferred consideration.

+ References

No definition available.

+ Details

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Namespace Prefix:	wetf_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Cash consideration paid from proceeds arising from maturities of securities owned, at fair value.

+ References

No definition available.

+ Details

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

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- Details

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- Details

Name:	us-gaap_CreditFacilityAxis=us-gaap_RevolvingCreditFacilityMember
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Data Type:	na
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Period Type:

- Details

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Business Combination - Additional Information (Detail) - USD ($)		12 Months Ended
	Apr. 11, 2018	Dec. 31, 2018	Dec. 31, 2017
Gain (loss) on revaluation of deferred consideration		$ 12,220,000
Acquisition related costs		11,454,000	$ 4,832,000
Acquisition of ETFS Business [Member]
Gain (loss) on revaluation of deferred consideration		$ (740,000)	$ (2,380,000)
Business acquisition, cash paid	$ 253,000,000
Cash consideration paid from proceeds arising from maturities of securities owned, at fair value	$ 53,000,000
Business acquisition, number of shares to be issued	30,000,000
Business acquisition, number of common shares that the preferred stock is convertible into	14,750,000
Acquisition of ETFS Business [Member] \| Term Loan Facility [Member]
Borrowing under term loan facility	$ 200,000,000
Acquisition of ETFS Business [Member] \| Revolving Credit Facility [Member]
Revolving credit facility maximum borrowing capacity	$ 50,000,000
Acquisition of ETFS Business [Member] \| Common Stock [Member]
Business acquisition, number of shares to be issued	15,250,000
Series A Non-Voting Convertible Preferred Stock [Member] \| Acquisition of ETFS Business [Member]
Business acquisition, number of shares to be issued	14,750	14,750