Income Taxes (Details) (Consolidated Legg Mason, USD $) In Thousands, unless otherwise specified	12 Months Ended
	Mar. 31, 2013		Mar. 31, 2012		Mar. 31, 2011		Jul. 31, 2012	Jul. 31, 2011	Sep. 30, 2010
Consolidated Legg Mason
VA release related to the release of the VA on DTAs related to Australia and Singapore	$ 3,500
Components of income before income tax provision
Domestic	(264,342)		257,866		230,334
Foreign	(246,265)		45,217		134,863
Income (loss) before income tax provision (benefit)	(510,607)		303,083		365,197
Components of Income Tax Expense (Benefit), Continuing Operations
Federal	(74,185)		54,179		75,290
Foreign	(85,677)		(7,850)		18,788
State and local	9,003		25,723		25,356
Current	6,496		22,860		39,162
Deferred	(157,355)		49,192		80,272
Income tax provision (benefit)	(150,859)		72,052		119,434
Effective Income Tax Rate, Continuing Operations, Tax Rate Reconciliation
Tax provision at statutory U.S. federal income tax rate	(35.00%)		35.00%		35.00%
State income taxes, net of federal income tax benefit	1.50%	[1]	5.40%	[1]	4.90%	[1]
Effect of foreign tax rates	3.80%	[1]	(1.80%)	[1]	(5.40%)	[1]
Effect of loss on Australian restructuring	0.00%		(6.00%)		0.00%
Changes in U.K. tax rates on deferred tax assets and liabilities	(3.50%)		(6.00%)		(2.50%)
Net (income) loss attributable to noncontrolling interests	0.50%		(0.80%)		0.80%
Other, net	3.20%	[1]	(2.00%)	[1]	(0.10%)	[1]
Effective income tax rate	(29.50%)		23.80%		32.70%
Foreign Corporate Tax Rate
Foreign Corporate Tax Rate Before Enactment, Finance Act of 2010									28.00%
Foreign Corporate Tax Rate After Enactment of Finance Act of 2010, Effective April 1, 2011									27.00%
Foreign Corporate tax rate after enactment of finance act of 2011, effective April 1, 2011								26.00%
Foreign Corporate tax rate after enactment of finance act of 2011, effective April 1, 2012								25.00%
Foreign Corporate Tax Rate After Enactment of Finance Act of 2012, Effective April 1, 2012							24.00%
Foreign Corporate Tax Rate After Enactment of Finance Act of 2012, Effective April 1, 2013							23.00%
Tax Benefit Resulting from Foreign Tax Rate Change	18,075		18,268		8,878
Australia restructuring tax benefit			18,254
Deferred tax assets
Accrued compensation and benefits	107,411		125,797
Accrued expenses	73,181		62,410
Operating loss carryforwards	449,806		397,013
Capital loss carryforwards	41,256		46,244
Convertible debt obligations	0		4,951
Foreign tax credit carryforward	115,819		59,871
Federal benefit of uncertain tax positions	21,165		17,602
Mutual fund launch costs	24,324		14,476
Net unrealized losses from investments	4,447		5,327
Other	5,086		18,119
Deferred tax assets	842,495		751,810
Valuation allowance	(115,815)		(102,722)
Deferred tax assets after valuation allowance	726,680		649,088
Deferred tax liabilities
Basis differences, principally for intangible assets and goodwill	134,873		196,611
Depreciation and amortization	386,959		431,280
Other	1,528		3,667
Deferred tax liabilities	523,360		631,558
Net deferred tax asset	$ 203,320		$ 17,530

[1] State income taxes include changes in valuation allowances, net of the impact on deferred tax assets of changes in state apportionment factors and planning strategies. The effect of foreign tax rates also includes changes in valuation allowances. Other includes changes in federal valuation allowances. See schedule below for the change in valuation allowances by jurisdiction.