Information about Outstanding Shares of Equity (Details 1) (USD $) In Thousands, except Share data, unless otherwise specified	1 Months Ended		12 Months Ended
	May 31, 2012	May 31, 2008	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2012
Class of Stock [Line Items]
Common Stock, Shares Authorized			500,000,000
Preferred Stock, Shares Authorized			4,000,000
Stock Repurchase Program, Authorized Amount	$ 1,000,000
Shares repurchased and retired, in dollars			359,996	425,475	400,266
Stock Repurchased and Retired During Period, Shares			9,677,000	16,199,000	13,597,000
Stock Repurchase Program, Remaining Authorized Repurchase Amount			370,000
Proceeds from Equity Units Issued		1,150,000
Interest Percentage in Senior Notes Per Equity Unit, Issued		5.00%
Stock Issued During Period, Shares, Conversion of Units					1,830,000
Legg Mason, Inc
Class of Stock [Line Items]
Common Stock, Capital Shares Reserved for Future Issuance			10,333,000	11,948,000
Shares repurchased and retired, in dollars	$ 155,000		$ 359,996	$ 425,475
Stock Repurchased and Retired During Period, Shares				16,199,000
2.5% convertible senior notes
Class of Stock [Line Items]
Class of Warrant or Right, Number of Securities Called by Warrants or Rights			14,205,000