Consolidated Statements of Changes in Stockholders' Equity - USD ($) $ in Thousands	Total	Consolidated Legg Mason, Inc.	Consolidated Legg Mason, Inc. COMMON STOCK	Consolidated Legg Mason, Inc. ADDITIONAL PAID-IN CAPITAL	Consolidated Legg Mason, Inc. EMPLOYEE STOCK TRUST	Consolidated Legg Mason, Inc. DEFERRED COMPENSATION EMPLOYEE STOCK TRUST	Consolidated Legg Mason, Inc. RETAINED EARNINGS, UNAPPROPRIATED	Consolidated Legg Mason, Inc. ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS), NET	Consolidated Investment Vehicles [Member]
Beginning Balance at Mar. 31, 2014			$ 11,717	$ 3,148,396	$ (29,922)	$ 29,922	$ 1,526,662	$ 37,949
Stock options exercised			50	14,123
Deferred compensation employee stock trust			3	1,707
Stock-based compensation			98	26,854
Adjustments to Additional Paid in Capital, Other				0
Employee tax withholdings by settlement of net share transactions			(46)	(21,386)
Shares repurchased and retired	$ (180,021)		(371)	(179,650)
Shares Issued to plans					(1,710)	1,710
Distributions and forfeitures					518	(518)
Net Income Attributable to Legg Mason, Inc.		$ 77,085					77,085		$ 1,808
Dividends declared							(37,764)
RE Reclassified for MEP Amortization							0
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Net Unamortized Gain (Loss) Arising During Period, before Tax		0						0
Reclassification for assets held for sale								(114)
Foreign currency translation adjustment		(21,524)						(21,524)
Ending Balance at Sep. 30, 2014		4,583,789	11,451	2,990,044	(31,114)	31,114	1,565,983	16,311
Beginning Balance at Mar. 31, 2015		4,484,901	11,147	2,844,441	(29,570)	29,570	1,690,055	(60,742)
Stock options exercised			22	6,073
Deferred compensation employee stock trust			1	250
Stock-based compensation			11	35,881
Adjustments to Additional Paid in Capital, Other				9,173
Employee tax withholdings by settlement of net share transactions			(40)	(21,138)
Shares repurchased and retired	$ (157,978)		(320)	(157,658)
Shares Issued to plans					(251)	251
Distributions and forfeitures					2,143	(2,143)
Net Income Attributable to Legg Mason, Inc.		158,867					158,867		$ (2,116)
Dividends declared							(44,162)
RE Reclassified for MEP Amortization							(826)
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Net Unamortized Gain (Loss) Arising During Period, before Tax		2,990						2,990
Reclassification for assets held for sale								0
Foreign currency translation adjustment		(16,512)						(16,512)
Ending Balance at Sep. 30, 2015		$ 4,457,513	$ 10,821	$ 2,717,022	$ (27,678)	$ 27,678	$ 1,803,934	$ (74,264)