Consolidated Statements of Cash Flows - USD ($) $ in Thousands		3 Months Ended
		Jun. 30, 2017	Jun. 30, 2016
CASH FLOWS FROM FINANCING ACTIVITIES
Noncontrolling Interest, Decrease from Distributions to Noncontrolling Interest Holders		$ (15,913)	$ (1,504)
Proceeds from (Payments to) Noncontrolling Interests		10,266	21,371
Consolidated Legg Mason, Inc.
CASH FLOWS FROM OPERATING ACTIVITIES
Net Income		63,537	45,340
Adjustments to reconcile Net Income to net cash used in operations:
Impairment of Intangible Assets, Indefinite-lived (Excluding Goodwill)		34,000	0
Depreciation and amortization		18,473	20,918
Accretion and amortization of securities discounts and premiums, net		936	659
Stock-based compensation		21,068	37,471
Deferred income taxes		22,183	16,093
Contingent consideration fair value adjustments		(16,550)	(18,000)
Other		(76)	1,419
Decrease (increase) in assets:
Investment advisory and related fees receivable		(46,340)	4,564
Net (purchases) sales of trading and other current investments		41,370	16,392
Other receivables		(9,778)	(8,930)
Increase (decrease) in liabilities:
Accrued compensation		(201,486)	(236,848)
Deferred compensation		15,718	20,076
Accounts payable and accrued expenses		12,378	17,145
CASH PROVIDED BY (USED IN) OPERATING ACTIVITIES		(113,580)	(165,970)
CASH FLOWS FROM INVESTING ACTIVITIES
Payments for fixed assets		(8,371)	(11,971)
Business acquisitions, net of cash acquired of $29,830		0	(997,933)
Proceeds from Sales of Assets, Investing Activities		2,561	0
Change in restricted cash		1,117	1,088
CASH PROVIDED BY (USED IN) INVESTING ACTIVITIES		(4,493)	(1,007,816)
CASH FLOWS FROM FINANCING ACTIVITIES
Issuance of common stock for stock-based compensation		7,532	1,933
Employee Tax Withholdings by settlement of net share transaction		(12,811)	(11,661)
Repurchase of common stock		(89,649)	(111,673)
Dividends paid		(21,153)	(21,878)
Noncontrolling Interest, Decrease from Distributions to Noncontrolling Interest Holders		17,731	2,306
CASH PROVIDED BY (USED IN) FINANCING ACTIVITIES		(123,546)	334,980
Consolidated Entity Excluding Consolidated Investment Vehicles Before Eliminations [Member]
Income Taxes Paid, Net		8,132	5,483
Adjustments to reconcile Net Income to net cash used in operations:
Unrealized Gain (Loss) on Investments		(5,496)	(3,107)
Net (gains) losses on investments		(5,546)	(2,568)
Decrease (increase) in assets:
Other assets		(1,330)	3,685
Increase (decrease) in liabilities:
Other liabilities		(23,855)	(38,509)
CASH FLOWS FROM INVESTING ACTIVITIES
Cash Acquired		33,543
Proceeds from sales and maturities of investment securities		200	1,000
CASH FLOWS FROM FINANCING ACTIVITIES
Proceeds from Lines of Credit		0	460,000
Debt issuance costs		0	(806)
EFFECT OF EXCHANGE RATES ON CASH		(789)	368
NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS		(242,408)	(838,438)
CASH AND CASH EQUIVALENTS AT BEGINNING OF YEAR		733,709	1,329,126
CASH AND CASH EQUIVALENTS AT END OF YEAR		491,301	490,688
Interest Paid		11,094	5,842
Proceeds from Income Tax Refunds		(1,903)	0
Consolidated Investment Vehicles [Member]
Adjustments to reconcile Net Income to net cash used in operations:
Net (gains) losses on investments		(997)	(3,199)
Decrease (increase) in assets:
Other assets		(32,803)	(40,705)
Increase (decrease) in liabilities:
Other liabilities		1,014	2,134
CASH FLOWS FROM FINANCING ACTIVITIES
Proceeds from (Payments to) Noncontrolling Interests		10,266	21,371
CASH AND CASH EQUIVALENTS AT BEGINNING OF YEAR		651
CASH AND CASH EQUIVALENTS AT END OF YEAR		679
Change in Input Assumptions [Member] | Consolidated Legg Mason, Inc.
Adjustments to reconcile Net Income to net cash used in operations:
Contingent consideration fair value adjustments		(16,550)	(18,000)
Consolidated Investment Vehicles [Member]
CASH FLOWS FROM FINANCING ACTIVITIES
Noncontrolling Interest, Decrease from Distributions to Noncontrolling Interest Holders		0	0
Proceeds from (Payments to) Noncontrolling Interests	[1],[2]	$ 10,266	18,767
Management Equity Plan [Member] | Clarion Partners [Member]
Adjustments to reconcile Net Income to net cash used in operations:
Deferred Compensation Arrangement with Individual, Allocated Share-based Compensation Expense			$ 15,200

[1] (1) Principally related to VIE and seeded investment products.

[2] (3) Includes the impact related to the adoption of updated consolidation accounting guidance.