Components Intangible Assets (Details 1) - USD ($) $ in Thousands	Mar. 31, 2019	Mar. 31, 2018
Finite-Lived and Indefinite-lived Intangible Assets
Cost	$ 366,930	$ 376,996
Accumulated amortization	(240,488)	(218,076)
Total	126,442	158,920
Indefinite-life intangible assets	3,260,317	3,638,739
U.S. Domestic Mutual Fund Management Contracts
Finite-Lived and Indefinite-lived Intangible Assets
Indefinite-life intangible assets	2,106,351	2,106,351
Other Fund Management Contracts [Member]
Finite-Lived and Indefinite-lived Intangible Assets
Indefinite-life intangible assets	473,360	557,305
Trade Names
Finite-Lived and Indefinite-lived Intangible Assets
Indefinite-life intangible assets	48,602	68,479
EnTrust Global [Member] \| Fund management contracts [Member]
Finite-Lived and Indefinite-lived Intangible Assets
Indefinite-life intangible assets	126,804	401,404
Clarion Partners [Member] \| Fund management contracts [Member]
Finite-Lived and Indefinite-lived Intangible Assets
Indefinite-life intangible assets	505,200	505,200
Consolidated Legg Mason, Inc.
Finite-Lived and Indefinite-lived Intangible Assets
Intangible assets, net	$ 3,386,759	$ 3,797,659

Finite-Lived and Indefinite-Lived Intangible Assets [Line Items]

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Accumulated amount of amortization of assets, excluding financial assets and goodwill, lacking physical substance with a finite life.

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Amount before amortization of assets, excluding financial assets and goodwill, lacking physical substance with a finite life.

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 928
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Amount after amortization of assets, excluding financial assets and goodwill, lacking physical substance with a finite life.

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

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Sum of the carrying amounts of all intangible assets, excluding goodwill, as of the balance sheet date, net of accumulated amortization and impairment charges.

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