Consolidated Statements of Comprehensive Income (Loss) (Consolidated Legg Mason [Domain], USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2012	Dec. 31, 2011
Consolidated Legg Mason [Domain]
Net Income (Loss)	$ (458,550)	$ 35,141	$ (390,439)	$ 154,222
Other comprehensive income (loss):
Foreign currency translation adjustment	(7,107)	3,309	(12,576)	(29,357)
Unrealized gains (losses) on investment securities:
Unrealized holding gains (losses), net of tax provision (benefit) of ($30), ($2), $14 and $167, respectively	(45)	(3)	21	250
Reclassification adjustment for (gains) losses included in net income (loss)	8	4	6	8
Net unrealized gains (losses) on investment securities	(37)	1	27	258
Total other comprehensive income (loss)	(7,144)	3,310	(12,549)	(29,099)
Comprehensive Income (Loss)	(465,694)	38,451	(402,988)	125,123
Less: Comprehensive income (loss) attributable to noncontrolling interests	(4,680)	7,009	(7,908)	9,474
Comprehensive Income (Loss) Attributable to Legg Mason, Inc.	$ (461,014)	$ 31,442	$ (395,080)	$ 115,649