Consolidated Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Sep. 30, 2015	Sep. 30, 2014
CASH FLOWS FROM OPERATING ACTIVITIES
Payments of Debt Extinguishment Costs	$ 0	$ 107,074
Consolidated Legg Mason, Inc.
CASH FLOWS FROM OPERATING ACTIVITIES
Net Income	157,858	78,633
Adjustments to reconcile Net Income to net cash used in operations:
Depreciation and amortization	27,534	27,985
Accretion and amortization of securities discounts and premiums, net	424	545
Stock-based compensation	37,041	34,699
Deferred income taxes	46,749	4,639
Other	701	(1,251)
Decrease (increase) in assets:
Investment advisory and related fees receivable	37,970	1,997
Net (purchases) sales of trading and other current investments	(12,373)	71,301
Other receivables	(10,884)	(5,720)
Increase (decrease) in liabilities:
Accrued compensation	(134,114)	(157,657)
Deferred compensation	12,123	2,172
Accounts payable and accrued expenses	(18,376)	(5,797)
CASH PROVIDED BY (USED IN) OPERATING ACTIVITIES	151,708	131,621
CASH FLOWS FROM INVESTING ACTIVITIES
Payments for fixed assets	(19,858)	(20,604)
Business acquisitions, net of cash acquired of $29,830	0	(10,558)
Change in restricted cash	18,438	2,988
CASH PROVIDED BY (USED IN) INVESTING ACTIVITIES	8,045	(28,127)
CASH FLOWS FROM FINANCING ACTIVITIES
Business Acquisition, Preacquisition Contingency, Amount of Settlement	(22,765)	0
Issuance of common stock for stock-based compensation	6,346	15,883
Employee Tax Withholdings by settlement of net share transaction	(21,178)	(21,432)
Repurchase of common stock	(157,978)	(180,021)
Dividends paid	(40,383)	(34,759)
CASH PROVIDED BY (USED IN) FINANCING ACTIVITIES	(202,817)	(290,072)
Consolidated Entity Excluding Consolidated Investment Vehicles Before Eliminations [Member]
CASH FLOWS FROM OPERATING ACTIVITIES
Net Income	159,189	77,352
Adjustments to reconcile Net Income to net cash used in operations:
Net (gains) losses on investments	16,688	(2,149)
Decrease (increase) in assets:
Other assets	16,892	14,524
Increase (decrease) in liabilities:
Other liabilities	(23,355)	(19,489)
CASH FLOWS FROM INVESTING ACTIVITIES
Purchases of investment securities	0	(2,641)
Proceeds from sales and maturities of investment securities	9,465	2,688
CASH FLOWS FROM FINANCING ACTIVITIES
Repayment of long-term debt	0	(645,561)
Proceeds from issuance of long-term debt	0	658,769
Debt issuance costs	0	(4,529)
EFFECT OF EXCHANGE RATES ON CASH	(7,553)	(12,470)
NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS	(50,617)	(199,048)
CASH AND CASH EQUIVALENTS AT BEGINNING OF YEAR	669,552	858,022
CASH AND CASH EQUIVALENTS AT END OF YEAR	618,935	658,974
Consolidated Investment Vehicles [Member]
CASH FLOWS FROM OPERATING ACTIVITIES
Net Income	(2,116)	2,484
Adjustments to reconcile Net Income to net cash used in operations:
Net (gains) losses on investments	1,011	(2,124)
Decrease (increase) in assets:
Other assets	(4,040)	87,989
Increase (decrease) in liabilities:
Other liabilities	(141)	(7,332)
CASH FLOWS FROM FINANCING ACTIVITIES
Repayment of long-term debt	0	(79,179)
Net subscriptions received from noncontrolling interests		757
CASH AND CASH EQUIVALENTS AT BEGINNING OF YEAR	2,808
CASH AND CASH EQUIVALENTS AT END OF YEAR	25
5.5% Senior Notes [Member] | Consolidated Legg Mason, Inc.
CASH FLOWS FROM OPERATING ACTIVITIES
Payments of Debt Extinguishment Costs	0	107,074
Make Whole Premium [Member] | 5.5% Senior Notes [Member] | Consolidated Legg Mason, Inc.
CASH FLOWS FROM OPERATING ACTIVITIES
Payments of Debt Extinguishment Costs	$ 0	$ (98,418)