Intangible Assets and Goodwill (Details 2) (Legg Mason Group, USD $) In Thousands, unless otherwise specified	3 Months Ended	9 Months Ended
Dec. 31, 2012 Indefinite-Life Intangible Assets	Dec. 31, 2012 U.S. domestic mutual fund management contracts	Dec. 31, 2012 Permal funds-of-hedge fund management contracts	Dec. 31, 2012 Permal trade names	Dec. 31, 2012 Impairment of Intangible Assets
Number of impairments	2			1
Impairment of Intangible Assets (Excluding Goodwill)		$ 396,000	$ 321,000	$ 17,000	$ 734,000
Projected Cash Flow Growth Rate, Low End of Range		3.00%	(1.00%)	(1.00%)
Projected Cash Flow Growth Rate, High End of Range		9.00%	17.00%	17.00%
Projected Cash Flow Growth Rate, Average		6.00%	8.00%	8.00%
Discount rate		14.50%	16.00%	16.00%

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

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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.

+ Details

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- Definition

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

+ References

No definition available.

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- Definition

Total numbers of impairments of intangible assets or goodwill

+ 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

-Subparagraph (bbb)

-URI http://asc.fasb.org/extlink&oid=7578670&loc=d3e19207-110258

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- Definition

The amount of impairment loss recognized in the period resulting from the write-down of the carrying amount of an intangible asset (excluding goodwill) to fair value.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 28

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=6943989&loc=d3e3602-108585

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 350

-SubTopic 30

-Section 50

-Paragraph 3

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-URI http://asc.fasb.org/extlink&oid=7658586&loc=d3e16373-109275

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-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 142

-Paragraph 46

-Subparagraph b

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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