Variable Interest Entities and Consolidation of Investment Vehicles (Details 9) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013		Mar. 31, 2012
CLO
Variable Interest Entity
Equity Interests on the Consolidated Balance Sheet	$ 0		$ 0
Maximum Risk of Loss	496	[1]	442	[1]
Real Estate Investment Trusts
Variable Interest Entity
Equity Interests on the Consolidated Balance Sheet	989
Maximum Risk of Loss	2,644	[1]
Public-Private Investment Program
Variable Interest Entity
Equity Interests on the Consolidated Balance Sheet			282	[2]
Maximum Risk of Loss			282	[1],[2]
Other sponsored investment funds
Variable Interest Entity
Equity Interests on the Consolidated Balance Sheet	43,104		54,161
Maximum Risk of Loss	87,121	[1]	93,521	[1]
Variable Interest Entity, Not Primary Beneficiary
Variable Interest Entity
Equity Interests on the Consolidated Balance Sheet	44,093		54,443
Maximum Risk of Loss	90,261	[1]	94,245	[1]
AUM of unconsolidated VIEs	$ 17,090,267		$ 17,534,840

[1] Includes equity investments the Company has made or is required to make and any earned but uncollected management fees.

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