Fair Values of Assets and Liabilities (Details 2) (Legg Mason Group, USD $) In Thousands, unless otherwise specified	12 Months Ended
Mar. 31, 2013	Mar. 31, 2012
Fair Value Assets and Liabilities Measured on Recurring Basis Financial Statement Unobservable Input Level 3
Assets measured at fair value using significant unobservable inputs, value at beginning of period	$ 207,103	$ 199,925
Purchases	3,073	32,815
Sales	(3,238)	(18,293)
Redemptions/Settlements/Other	(130,130)	(14,905)
Transfers, Net	0	0
Realized and unrealized gains/(losses), net	17,649	7,561
Assets measured at fair value using significant unobservable inputs, value at end of period	94,457	207,103
Unrealized gains (losses) on Level 3 assets and liabilities still held at the reporting date	(1,229)	5,495
Trading proprietary fund products and other investments
Fair Value Assets and Liabilities Measured on Recurring Basis Financial Statement Unobservable Input Level 3
Assets measured at fair value using significant unobservable inputs, value at beginning of period	0	11,378
Purchases	246	0
Sales	0	(11,906)
Redemptions/Settlements/Other	0	0
Transfers, Net	0	0
Realized and unrealized gains/(losses), net	0	528
Assets measured at fair value using significant unobservable inputs, value at end of period	246	0
Equity method investments in proprietary fund products
Fair Value Assets and Liabilities Measured on Recurring Basis Financial Statement Unobservable Input Level 3
Assets measured at fair value using significant unobservable inputs, value at beginning of period	11,778	12,167
Purchases	0	0
Sales	0	0
Redemptions/Settlements/Other	(11,705)	0
Transfers, Net	0	0
Realized and unrealized gains/(losses), net	(73)	(389)
Assets measured at fair value using significant unobservable inputs, value at end of period	0	11,778
Investments in partnerships, LLCs and other
Fair Value Assets and Liabilities Measured on Recurring Basis Financial Statement Unobservable Input Level 3
Assets measured at fair value using significant unobservable inputs, value at beginning of period	28,763	22,167
Purchases	0	6,932
Sales	(970)	0
Redemptions/Settlements/Other	(1,014)	(578)
Transfers, Net	0	0
Realized and unrealized gains/(losses), net	983	242
Assets measured at fair value using significant unobservable inputs, value at end of period	27,762	28,763
Equity method investments in partnerships and LLCs
Fair Value Assets and Liabilities Measured on Recurring Basis Financial Statement Unobservable Input Level 3
Assets measured at fair value using significant unobservable inputs, value at beginning of period	166,438	153,931
Purchases	2,827	25,883
Sales	(2,268)	(6,387)
Redemptions/Settlements/Other	(117,411)	(14,168)
Transfers, Net	0	0
Realized and unrealized gains/(losses), net	16,752	7,179
Assets measured at fair value using significant unobservable inputs, value at end of period	66,338	166,438
Other Investments
Fair Value Assets and Liabilities Measured on Recurring Basis Financial Statement Unobservable Input Level 3
Assets measured at fair value using significant unobservable inputs, value at beginning of period	124	282
Purchases	0	0
Sales	0	0
Redemptions/Settlements/Other	0	(159)
Transfers, Net	0	0
Realized and unrealized gains/(losses), net	(13)	1
Assets measured at fair value using significant unobservable inputs, value at end of period	$ 111	$ 124

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This element represents total gains or losses for the period (unrealized), arising from assets and liabilities still held at the reporting date measured at fair value on a recurring basis using unobservable inputs (Level 3), which are included in earnings or resulted in a change in net asset value.

+ References

No definition available.

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- Definition

Amount of gain (loss) recognized in earnings, arising from assets measured at fair value on a recurring basis using unobservable inputs (level 3).

+ References

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- Definition

Purchases that have taken place during the period in relation to assets measured at fair value and categorized within Level 3 of the fair value hierarchy.

+ References

+ Details

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- Definition

Sales that have taken place during the period in relation to assets measured at fair value and categorized within Level 3 of the fair value hierarchy.

+ References

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- Definition

Settlements that have taken place during the period in relation to assets measured at fair value and categorized within Level 3 of the fair value hierarchy.

+ References

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- Definition

This element represents [net] transfers in to and out of assets measured at fair value on a recurring basis using unobservable inputs (Level 3) which have taken place during the period.

+ References

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 157

-Paragraph 32

-Subparagraph c(3)

-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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- Definition

This element represents an asset measured at fair value using significant unobservable inputs (Level 3) which is required for reconciliation purposes of beginning and ending balances.

+ 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 (c)

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

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 157

-Paragraph 32

-Subparagraph c

-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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