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	Consolidated Legg Mason, Inc. ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS), NET	Consolidated Investment Vehicles [Member]		Clarion Partners [Member] Consolidated Legg Mason, Inc. ADDITIONAL PAID-IN CAPITAL	EnTrust Capital [Member] Consolidated Legg Mason, Inc. RETAINED EARNINGS	Management Equity Plan [Member] Consolidated Legg Mason, Inc. RETAINED EARNINGS
Stockholders' Equity Attributable to Parent			$ 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							$ 0
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)
APIC reclassified for MEP vesting	(826)			0
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)
Reclassification from Retained Earnings to Noncontrolling Interests												$ 0	$ (826)
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Net Unamortized Gain (Loss) Arising During Period, before Tax		2,990						2,990
Foreign currency translation adjustment		(16,512)
Ending Balance at Sep. 30, 2015		4,457,513
Stockholders' Equity Attributable to Parent		4,457,513	10,821	2,717,022	(27,678)	27,678	1,803,934	(74,264)
Stockholders' Equity Attributable to Noncontrolling Interest		0
Stockholders' Equity Attributable to Parent		4,213,563	10,701	2,693,113	(26,263)	26,263	1,576,242	(66,493)
Beginning Balance at Mar. 31, 2016		4,235,765
Stock options exercised			12	3,442
Deferred compensation employee stock trust			1	254
Stock-based compensation			37	43,773							$ 11,121
Adjustments to Additional Paid in Capital, Other				0
Employee tax withholdings by settlement of net share transactions			(36)	(11,766)
Shares repurchased and retired	$ (201,673)		(617)	(201,056)
APIC reclassified for MEP vesting				(3,632)
Shares Issued to plans					(255)	255
Distributions and forfeitures					1,067	(1,067)
Net Income Attributable to Legg Mason, Inc.		99,893					99,893		$ 8,860	[1]
Dividends declared							(46,039)
Reclassification from Retained Earnings to Noncontrolling Interests												$ (15,500)	$ (1,721)
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Net Unamortized Gain (Loss) Arising During Period, before Tax		(19,159)						(19,159)
Foreign currency translation adjustment		(13,023)
Ending Balance at Sep. 30, 2016		4,082,733
Stockholders' Equity Attributable to Parent		$ 4,059,547	$ 10,098	$ 2,535,249	$ (25,451)	$ 25,451	$ 1,612,875	$ (98,675)

[1] Other represents consolidated sponsored investment products that are not designated as CIVs.