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Goodwill and Other Intangible Assets - Indefinite-Lived Intangible Assets (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Indefinite Lived Intangible Assets
Net carrying amount of unamortized indefinite lived intangible assets	$ 790.4	$ 783.6
WM Advisors, Inc.
Indefinite Lived Intangible Assets
Net carrying amount of unamortized indefinite lived intangible assets	$ 608.0	$ 608.0

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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.

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- Definition

Amount of assets, excluding financial assets and goodwill, lacking physical substance and having a projected indefinite period of benefit.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 30
-Section 50
-Paragraph 2
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=66006027&loc=d3e16323-109275

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