Consolidated Statements of Income - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Payments of Debt Extinguishment Costs	$ 0	$ 107,074	$ 0	$ 107,074
Consolidated Legg Mason, Inc.
OPERATING REVENUES
Distribution and service fees	99,602	94,481	196,462	184,197
Other	556	1,444	1,244	2,909
Total Operating Revenues	673,086	703,895	1,381,736	1,397,776
OPERATING EXPENSES
Compensation and benefits	282,433	303,878	597,485	609,384
Distribution and servicing	138,930	155,100	288,218	303,808
Communications and technology	49,845	44,624	98,522	86,574
Occupancy	25,716	22,710	51,703	49,667
Amortization of intangible assets	670	464	1,327	1,359
Other	42,462	46,764	86,908	97,083
Total Operating Expenses	540,056	573,540	1,124,163	1,147,875
OPERATING INCOME	133,030	130,355	257,573	249,901
OTHER NON-OPERATING INCOME (EXPENSE)
Interest income	1,229	1,680	2,546	4,205
Interest expense	(13,280)	(14,975)	(25,229)	(32,033)
Other income (expense), net	(28,110)	(108,156)	(22,399)	(101,908)
Total Other Non-Operating Income (Expense)	(42,464)	(121,530)	(46,978)	(126,808)
INCOME BEFORE INCOME TAX PROVISION	90,566	8,825	210,595	123,093
Income tax provision	27,647	3,804	52,737	44,460
NET INCOME	62,919	5,021	157,858	78,633
Net Income (Loss) Attributable to Noncontrolling Interest	(1,400)	124	(1,009)	1,548
NET INCOME ATTRIBUTABLE TO LEGG MASON, INC.	$ 64,319	$ 4,897	$ 158,867	$ 77,085
NET INCOME PER SHARE ATTRIBUTABLE TO LEGG MASON, INC. COMMON SHAREHOLDERS
Basic (in dollars per share)	$ 0.58	$ 0.04	$ 1.43	$ 0.66
Diluted (in dollars per share)	0.58	0.04	1.42	0.66
Common Stock, Dividends, Per Share, Declared	$ 0.20	$ 0.16	$ 0.40	$ 0.32
Consolidated Entity Excluding Consolidated Investment Vehicles Before Eliminations [Member]
OPERATING REVENUES
Total Operating Revenues	$ 673,168	$ 704,079	$ 1,381,903	$ 1,398,143
OPERATING EXPENSES
Total Operating Expenses	540,023	573,486	1,124,110	1,147,801
OPERATING INCOME	133,145	130,593	257,793	250,342
OTHER NON-OPERATING INCOME (EXPENSE)
Total Other Non-Operating Income (Expense)	(40,988)	(121,714)	(45,867)	(128,530)
INCOME BEFORE INCOME TAX PROVISION	92,157	8,879	211,926	121,812
Income tax provision	27,647	3,804	52,737	44,460
NET INCOME	64,510	5,075	159,189	77,352
Net Income (Loss) Attributable to Noncontrolling Interest	191	178	322	267
NET INCOME ATTRIBUTABLE TO LEGG MASON, INC.	64,319	4,897	158,867	77,085
Consolidated Investment Vehicles [Member]
OPERATING REVENUES
Total Operating Revenues	0	0	0	0
OPERATING EXPENSES
Total Operating Expenses	115	238	220	441
OPERATING INCOME	(115)	(238)	(220)	(441)
OTHER NON-OPERATING INCOME (EXPENSE)
Other income (expense), net	(2,303)	(79)	(1,896)	2,928
Total Other Non-Operating Income (Expense)	(2,303)	(82)	(1,896)	2,925
INCOME BEFORE INCOME TAX PROVISION	(2,418)	(320)	(2,116)	2,484
Income tax provision	0	0	0	0
NET INCOME	(2,418)	(320)	(2,116)	2,484
Net Income (Loss) Attributable to Noncontrolling Interest	0	(392)	0	676
NET INCOME ATTRIBUTABLE TO LEGG MASON, INC.	(2,418)	72	(2,116)	1,808
Separate Accounts [Member] | Consolidated Legg Mason, Inc.
OPERATING REVENUES
Investment Advisory Fees	205,155	204,739	413,259	409,509
Mutual Funds [Member] | Consolidated Legg Mason, Inc.
OPERATING REVENUES
Investment Advisory Fees	359,871	389,238	744,216	770,865
Performance Fees [Member] | Consolidated Legg Mason, Inc.
OPERATING REVENUES
Investment Advisory Fees	$ 7,902	$ 13,993	$ 26,555	$ 30,296