Exit Activities - Schedule of Operating Losses (Parenthetical) (Detail) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
Sep. 30, 2021	Mar. 31, 2021	Sep. 30, 2020	Mar. 31, 2020	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Impairment expenses	$ 15,853	$ 303	$ 3,080	$ 19,672	$ 16,156	$ 22,752	$ 30,710
WisdomTree Japan Inc. ("WTJ") [Member]
Impairment expenses							$ 572

Amount of write-down of assets recognized in the income statement. Includes, but is not limited to, losses from tangible assets, intangible assets and goodwill.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=123570139&loc=d3e3602-108585

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 360
-SubTopic 10
-Section 45
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=123351718&loc=d3e2420-110228

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration