VIE Consolidated Income Statements Details (Details 2) - USD ($) $ in Thousands	3 Months Ended
	Jun. 30, 2015	Jun. 30, 2014
Condensed Income Statements, Captions [Line Items]
Less: Net income attributable to noncontrolling interests	$ 391	$ 1,424
Balance Before Consolidation of CIVs
Condensed Income Statements, Captions [Line Items]
Total Operating Revenues	708,735	694,064
Total Operating Expenses	584,087	574,315
OPERATING INCOME	124,648	119,749
Total Other Non-Operating Income (Expense)	(4,879)	(6,816)
INCOME BEFORE INCOME TAX PROVISION	119,769	112,933
Income tax provision	25,090	40,656
NET INCOME	94,679	72,277
Less: Net income attributable to noncontrolling interests	131	89
Net Income Attributable to Legg Mason, Inc.	94,548	72,188
CIVs
Condensed Income Statements, Captions [Line Items]
Total Operating Revenues	0	0
Total Operating Expenses	105	203
OPERATING INCOME	(105)	(203)
Total Other Non-Operating Income (Expense)	407	3,007
INCOME BEFORE INCOME TAX PROVISION	302	2,804
Income tax provision	0	0
NET INCOME	302	2,804
Less: Net income attributable to noncontrolling interests	0	1,068
Net Income Attributable to Legg Mason, Inc.	302	1,736
Eliminations
Condensed Income Statements, Captions [Line Items]
Total Operating Revenues	(85)	(183)
Total Operating Expenses	(85)	(183)
OPERATING INCOME	0	0
Total Other Non-Operating Income (Expense)	(42)	(1,469)
INCOME BEFORE INCOME TAX PROVISION	(42)	(1,469)
Income tax provision	0	0
NET INCOME	(42)	(1,469)
Less: Net income attributable to noncontrolling interests	260	267
Net Income Attributable to Legg Mason, Inc.	(302)	(1,736)
Consolidated Legg Mason, Inc.
Condensed Income Statements, Captions [Line Items]
Total Operating Revenues	708,650	693,881
Total Operating Expenses	584,107	574,335
OPERATING INCOME	124,543	119,546
Total Other Non-Operating Income (Expense)	(4,514)	(5,278)
INCOME BEFORE INCOME TAX PROVISION	120,029	114,268
Income tax provision	25,090	40,656
NET INCOME	94,939	73,612
Less: Net income attributable to noncontrolling interests	391	1,424
Net Income Attributable to Legg Mason, Inc.	$ 94,548	$ 72,188