Income Taxes (Details 2) (Consolidated Legg Mason, USD $) In Thousands, unless otherwise specified	12 Months Ended
	Mar. 31, 2013	Mar. 31, 2011
Consolidated Legg Mason
NOL recognized as an increase in stockholders equity upon realization	$ 6,700
Adjustment to Additional Paid in Capital, Extinguishment of Equity Unit Tax Benefit		36,000
Deferred Tax Assets, Domestic, Federal	770,933
Future Earnings, Required for Realization of Deferred Tax Assets	4,200,000
Future Foreign Source Earnings Required for Realization of Deferred Tax Assets	331,606
Foreign Tax Credits for Which Valuation Allowance Has Been Recorded	36,319
Valuation Allowance, Deferred Tax Asset, Change in Amount	17,066
Deferred Tax Assets, State Taxes	172,704
Amount of Valuation Allowance on US State DTAs released	2,046
VA release related to the release of the VA on DTAs related to Australia and Singapore	$ 3,500