Significant Accounting Policies (Details 3) (Consolidated Legg Mason [Domain], USD $) In Thousands, unless otherwise specified	3 Months Ended	6 Months Ended
Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Consolidated Legg Mason [Domain]
Redeemable Noncontrolling Interest [Line Items]
Net income (loss) attributable to redeemable noncontrolling interests	$ 479	$ 4,376	$ (182)	$ 8,267
Net income (loss) reclassified to Appropriated retained earnings for consolidated investment vehicles	(181)	(3,657)	(3,046)	(5,802)
Total	$ 298	$ 719	$ (3,228)	$ 2,465

Amount of Net Income (Loss) attributable to noncontrolling interest.

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

-Publisher FASB

-Name Accounting Standards Codification

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

-Publisher AICPA

-Name Accounting Research Bulletin (ARB)

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Reference 3: http://www.xbrl.org/2003/role/presentationRef

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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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.

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

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-Publisher AICPA

-Name Accounting Research Bulletin (ARB)

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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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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