Fair Values of Assets and Liabilities (Details 3) (Legg Mason, Inc., USD $) In Thousands, unless otherwise specified	3 Months Ended		12 Months Ended
	Jun. 30, 2012		Mar. 31, 2012
Funds-of-hedge funds
Nature of Investments
Fair Value Determined Using Nav	$ 44,878	[1]	$ 51,251	[2]
Percentage of Monthly Redemption (as a percent)	59.00%		63.00%
Percentage of Quarterly Redemption (as a percent)	41.00%		37.00%
Percentage subject to lock-up or side pocket provisions (as a percent)	37.00%		36.00%
Hedge funds
Nature of Investments
Fair Value Determined Using Nav	26,367		25,460
Unfunded Commitments	20,000
Private equity funds
Nature of Investments
Fair Value Determined Using Nav	27,664	[3]	27,927	[3]
Unfunded Commitments	5,932
Remaining term, high end of range (in years)	8
Private fund
Nature of Investments
Fair Value Determined Using Nav	89,003	[3],[4]	89,323	[3],[4]
Number of extensions which may be made to the remaining terms	2
Remaining term, low end of range (in years)	6
Other
Nature of Investments
Fair Value Determined Using Nav	2,153	[5]	2,450
Percentage of investment with less than 1 year remaining term (as a percent)	4.00%
Percentage of investment with 20-year remaining term (as a percent)	96.00%
Remaining term, low end of range (in years)	1
Remaining term, high end of range (in years)	20
Investments
Nature of Investments
Fair Value Determined Using Nav	190,065	[6]	196,411	[6]
Unfunded Commitments	$ 25,932
Assets valued using net asset value as practical expedient - Level 2	13.00%		13.00%
Assets at fair value using net asset as practical expedient - Level 3	87.00%		87.00%

[1] 59% monthly redemption; 41% quarterly redemption, of which 37% is subject to two-year lock-up.

[2] 63% monthly redemption; 37% quarterly redemption, of which 36% is subject to two-year lock-up.

[3] Liquidations are expected over the remaining term.

[4] Redemptions prohibited until November 2012.

[5] 4% remaining term of less than one year and 96% 20-year remaining term.

[6] Comprised of approximately 13% and 87% of Level 2 and Level 3 assets, respectively, as of both June 30, 2012 and March 31, 2012.