Fair Values of Assets and Liabilities (Details 3) (Legg Mason Group, USD $) In Thousands, unless otherwise specified	3 Months Ended
	Dec. 31, 2012		Mar. 31, 2012
Funds-of-hedge funds
Nature of Investments
Fair Value Determined Using Nav	$ 45,481	[1]	$ 51,251	[2]
Percentage of Monthly Redemption (as a percent)	58.00%		63.00%
Percentage of Quarterly Redemption (as a percent)	42.00%		37.00%
Percentage subject to lock-up or side pocket provisions (as a percent)	38.00%		36.00%
Hedge funds
Nature of Investments
Fair Value Determined Using Nav	24,073		25,460
Unfunded Commitments	20,000
Private equity funds
Nature of Investments
Fair Value Determined Using Nav	25,591	[3]	27,927	[3]
Unfunded Commitments	5,218
Remaining term, high end of range (in years)	7
Private fund
Nature of Investments
Fair Value Determined Using Nav	0	[4]	89,323	[4]
Other
Nature of Investments
Fair Value Determined Using Nav	2,164	[5]	2,450	[5]
Percentage of investment with less than 1 year remaining term (as a percent)	3.00%
Percentage of investment with 20-year remaining term (as a percent)	97.00%
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	97,309	[6]	196,411	[6]
Unfunded Commitments	$ 25,218
Assets valued using net asset value as practical expedient - Level 2	37.00%		13.00%
Assets at fair value using net asset as practical expedient - Level 3	63.00%		87.00%

[1] 58% monthly redemption; 42% quarterly redemption, of which 38% is subject to two-year lock-up, which expires in June 2013.

[2] 63% monthly redemption; 37% quarterly redemption, of which 36% is subject to two-year lock-up, which expires in June 2013.

[3] Liquidations are expected over the remaining term.

[4] Legg Mason's investment was fully redeemed in the quarter ended December 31, 2012 upon liquidation of the fund.

[5] Of this balance, 3% has a remaining term of less than one year and 97% has a remaining term of 20 years.

[6] Comprised of approximately 37% and 63% of Level 2 and Level 3 assets, respectively, as of December 31, 2012 and 13% and 87% of Level 2 and Level 3 assets, respectively, as of March 31, 2012.