Change in Assets Under Management

No definition available.

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- Definition

Percentage of assumed growth rate in projected cash flows, used as an input to measure fair value, average

+ References

No definition available.

+ Details

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- Definition

Percentage of assumed growth rate in projected cash flows, used as an input to measure fair value, high end of range

+ References

No definition available.

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- Definition

Percentage of assumed royalties earned, used as an input to measure fair value.

+ References

No definition available.

+ Details

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- Definition

Amount used to represent the attrition when calculating the fair value of amortizable asset management contracts

+ References

No definition available.

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- Definition

Percentage of assumed long-term growth in AUM, used as an input to measure fair value.

+ References

No definition available.

+ Details

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- Definition

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.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 360
-SubTopic 10
-Section 45
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=68055307&loc=d3e2420-110228

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
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-URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3602-108585

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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

Interest rate used to find the present value of an amount to be paid or received in the future as an input to measure fair value. For example, but not limited to, weighted average cost of capital (WACC), cost of capital, cost of equity and cost of debt.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
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-URI http://asc.fasb.org/extlink&oid=66048111&loc=d3e19207-110258

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- Definition

Amount of impairment loss resulting from write-down of assets, excluding financial assets and goodwill, lacking physical substance and having a projected indefinite period of benefit to fair value.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 30
-Section 50
-Paragraph 3
-Subparagraph (b)
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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://www.xbrl.org/2003/role/presentationRef
-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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- Definition

Percentage of fair value of reporting unit in excess of carrying amount.

+ References

No definition available.

+ Details

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Intangible Assets and Goodwill Intangible Fair Value Assumptions (Details 2) - USD ($) $ in Thousands	3 Months Ended			6 Months Ended		12 Months Ended
	Sep. 30, 2017	Jun. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Mar. 31, 2016	Mar. 31, 2017
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Indefinite-Lived Intangible Assets (Excluding Goodwill)	$ 3,830,562			$ 3,830,562			$ 3,820,726
Assets Under Management [Member] \| RARE Infrastructure, Ltd [Member] \| Fair Value, Inputs, Level 3 [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value Input, Projected Cash Flow Growth Rate, Average						7.00%
Fair Value Inputs, Discount Rate						6.50%
Asset Management Contracts \| Fair Value, Inputs, Level 3 [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value Inputs, Long-term AUM Growth Rate		7.00%
Fair Value Inputs, Attrition Rate		20.00%
Fair Value Inputs, Discount Rate		16.50%
Asset Management Contracts \| RARE Infrastructure, Ltd [Member] \| Fair Value, Inputs, Level 3 [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value Inputs, Long-term AUM Growth Rate						7.00%
Fair Value Inputs, Attrition Rate						8.00%
Fair Value Inputs, Discount Rate						16.50%
Trade Names \| Fair Value, Inputs, Level 3 [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value Input, Projected Cash Flow Growth Rate, Average		8.00%
Fair Value Input, Royalty Rate		1.00%
Fair Value Inputs, Discount Rate		16.50%
Trade Names \| Maximum [Member] \| Fair Value, Inputs, Level 3 [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value Input, Projected Cash Flow Growth Rate, High End of Range		18.00%
Trade Names \| Minimum [Member] \| Fair Value, Inputs, Level 3 [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value Input, Projected Cash Flow Growth Rate, High End of Range		5.00%
Trade Names \| RARE Infrastructure, Ltd [Member] \| Fair Value, Inputs, Level 3 [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value Input, Projected Cash Flow Growth Rate, High End of Range			10.00%
Fair Value Input, Projected Cash Flow Growth Rate, Average			7.00%
Fair Value Inputs, Discount Rate			16.50%
Other Fund Management Contracts [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Indefinite-Lived Intangible Assets (Excluding Goodwill)	554,338			554,338			542,908
Trade Names
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Impairment of Intangible Assets		$ 2,000
Indefinite-Lived Intangible Assets (Excluding Goodwill)	68,269			68,269			$ 69,863
Consolidated Legg Mason, Inc.
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Impairment of Intangible Assets	0		$ 0
Impairment of Intangible Assets, Indefinite-lived (Excluding Goodwill)				34,000	$ 0
Permal [Member] \| Trade Names
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Indefinite-Lived Intangible Assets (Excluding Goodwill)	$ 21,100			$ 21,100
RARE Infrastructure, Ltd [Member] \| Other Fund Management Contracts [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Reporting Unit, Percentage of Fair Value in Excess of Carrying Amount		7.00%
Customer Contracts [Member] \| RARE Infrastructure, Ltd [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Change in Assets Under Management		$ 1,500,000
Impairment of Intangible Assets		32,000
Indefinite-Lived Intangible Assets (Excluding Goodwill)		$ 11,180