Consolidated Statements of Cash Flows - USD ($) $ in Thousands		12 Months Ended
		Mar. 31, 2017		Mar. 31, 2016	Mar. 31, 2015
CASH FLOWS FROM OPERATING ACTIVITIES
Payments of Debt Extinguishment Costs					$ 107,074
Adjustments to reconcile Net Income to net cash used in operations:
Impairment of Intangible Assets, Indefinite-lived (Excluding Goodwill)				$ 371,000
CASH FLOWS FROM FINANCING ACTIVITIES
Noncontrolling Interest, Decrease from Distributions to Noncontrolling Interest Holders		$ (29,461)
Proceeds from (Payments to) Noncontrolling Interests		(44,587)		66,658	(10,459)
CASH AND CASH EQUIVALENTS AT BEGINNING OF YEAR
CASH AND CASH EQUIVALENTS AT END OF YEAR		438,000
Consolidated Legg Mason, Inc.
CASH FLOWS FROM OPERATING ACTIVITIES
Net Income		286,703		(32,910)	242,709
Adjustments to reconcile Net Income to net cash used in operations:
Impairment of Intangible Assets, Indefinite-lived (Excluding Goodwill)		35,000		371,000	0
Depreciation and amortization		80,213		60,297	55,086
Accretion and amortization of securities discounts and premiums, net		5,691		3,140	4,275
Stock-based compensation		93,008		92,927	66,245
Deferred income taxes		57,804		(7,727)	100,387
Other		1,722		2,631	(12,939)
Decrease (increase) in assets:
Investment advisory and related fees receivable		(28,921)		34,308	(28,668)
Net (purchases) sales of trading and other current investments		98,473		(82,423)	47,357
Other receivables		(13,481)		(9,545)	19,547
Increase (decrease) in liabilities:
Accrued compensation		34,456		30,998	(17,727)
Deferred compensation		22,248		14,316	10,314
Accounts payable and accrued expenses		(16,082)		(7,593)	(14,763)
CASH PROVIDED BY (USED IN) OPERATING ACTIVITIES		539,772		454,451	568,118
CASH FLOWS FROM INVESTING ACTIVITIES
Payments for fixed assets		(39,977)		(40,330)	(45,773)
Business acquisitions, net of cash acquired of $29,830		(1,010,428)		(234,053)	(183,747)
Proceeds from Sales of Assets, Investing Activities		19,469		0	47,001
Change in restricted cash		2,982		21,065	(25,571)
CASH PROVIDED BY (USED IN) INVESTING ACTIVITIES		(1,019,665)		(244,569)	(208,043)
CASH FLOWS FROM FINANCING ACTIVITIES
Business Acquisition, Preacquisition Contingency, Amount of Settlement		(6,587)		(22,765)	0
Issuance of common stock for stock-based compensation		9,506		10,022	24,288
Employee Tax Withholdings by settlement of net share transaction		(12,139)		(21,637)	(22,114)
Repurchase of common stock		(381,672)		(209,632)	(356,522)
Dividends paid		(87,897)		(84,093)	(70,815)
Proceeds from (Payments to) Noncontrolling Interests		(35,862)		(1,016)	0
CASH PROVIDED BY (USED IN) FINANCING ACTIVITIES		(116,877)		465,772	(507,062)
Consolidated Entity Excluding Consolidated Investment Vehicles Before Eliminations [Member]
Income Taxes Paid, Net		21,552		23,743	19,578
Adjustments to reconcile Net Income to net cash used in operations:
Unrealized Gain (Loss) on Investments		(33,088)		39,460	24,058
Net (gains) losses on investments		(9,717)		(13,404)	37,970
Decrease (increase) in assets:
Other assets		(11,766)		4,947	(9,936)
Increase (decrease) in liabilities:
Other liabilities		(51,027)		(11,573)	1,182
CASH FLOWS FROM INVESTING ACTIVITIES
Cash Acquired		33,547		9,667	29,830
Payments to Acquire Marketable Securities		0		0	(2,641)
Proceeds from sales and maturities of investment securities		8,289		8,749	2,688
Proceeds from Lines of Credit		(40,000)		40,000	0
Repayments of Long-term Debt		0		0	645,780
CASH FLOWS FROM FINANCING ACTIVITIES
Proceeds from Issuance of Long-term Debt		500,000		699,793	658,769
Debt issuance costs		(17,639)		(13,539)	(5,250)
EFFECT OF EXCHANGE RATES ON CASH		1,353		(16,080)	(41,483)
NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS		(595,417)		659,574	(188,470)
CASH AND CASH EQUIVALENTS AT BEGINNING OF YEAR		1,329,126		669,552	858,022
CASH AND CASH EQUIVALENTS AT END OF YEAR		733,709		1,329,126	669,552
Interest Paid		105,381		49,393	59,039
Proceeds from Income Tax Refunds		(1,014)		(4,689)	(865)
Consolidated Investment Vehicles [Member]
Adjustments to reconcile Net Income to net cash used in operations:
Net (gains) losses on investments		(13,329)		2,496	(1,308)
Decrease (increase) in assets:
Other assets		45,177		(1,631)	114,934
Increase (decrease) in liabilities:
Other liabilities		(3,812)		(1,888)	(3,321)
CASH FLOWS FROM INVESTING ACTIVITIES
Repayments of Long-term Debt		0		0	79,179
CASH FLOWS FROM FINANCING ACTIVITIES
Proceeds from (Payments to) Noncontrolling Interests		(44,587)		68,639	(10,459)
CASH AND CASH EQUIVALENTS AT BEGINNING OF YEAR		297
CASH AND CASH EQUIVALENTS AT END OF YEAR		651		297
Change in Input Assumptions [Member] | Consolidated Legg Mason, Inc.
Adjustments to reconcile Net Income to net cash used in operations:
Business Combination, Contingent Consideration Arrangements, Change in Amount of Contingent Consideration, Liability		(39,500)		(33,375)	0
Consolidated Investment Vehicles [Member]
CASH FLOWS FROM FINANCING ACTIVITIES
Noncontrolling Interest, Decrease from Distributions to Noncontrolling Interest Holders		0
Proceeds from (Payments to) Noncontrolling Interests	[2]	(47,118)	[1]	68,639	(10,484)
5.5% Senior Notes [Member] | Consolidated Legg Mason, Inc.
CASH FLOWS FROM OPERATING ACTIVITIES
Payments of Debt Extinguishment Costs		0		0	107,074
Make Whole Premium [Member]
CASH FLOWS FROM OPERATING ACTIVITIES
Payments of Debt Extinguishment Costs					98,418
Make Whole Premium [Member] | 5.5% Senior Notes [Member] | Consolidated Legg Mason, Inc.
CASH FLOWS FROM OPERATING ACTIVITIES
Payments of Debt Extinguishment Costs		$ 0		$ 0	$ (98,418)

[1] Includes the impact related to the adoption of updated consolidation accounting guidance further discussed in Note 1.

[2] Principally related to VIE and seeded investment products.