Consolidated Statements of Cash Flows $ in Thousands	9 Months Ended
	Dec. 31, 2017 USD ($)		Dec. 31, 2016 USD ($)
CASH FLOWS FROM FINANCING ACTIVITIES
Noncontrolling Interest, Decrease from Distributions to Noncontrolling Interest Holders	$ (36,953)		$ (18,797)
Proceeds from (Payments to) Noncontrolling Interests	44,708		(18,310)
Consolidated Legg Mason, Inc.
CASH FLOWS FROM OPERATING ACTIVITIES
Net Income	319,707		196,399
Adjustments to reconcile Net Income to net cash used in operations:
Impairment of Intangible Assets, Indefinite-lived (Excluding Goodwill)	229,000		35,000
Depreciation and amortization	54,551		60,639
Accretion and amortization of securities discounts and premiums, net	(2,255)		(3,058)
Stock-based compensation	55,002		71,922
Deferred income taxes	46,650		59,729
Contingent consideration fair value adjustments	(15,811)		(39,500)
Other	196		(585)
Decrease (increase) in assets:
Investment advisory and related fees receivable	47,603		18,456
Net (purchases) sales of trading and other current investments	43,550		61,935
Other receivables	(5,471)		5,768
Increase (decrease) in liabilities:
Accrued compensation	(97,419)		12,068
Deferred compensation	10,633		21,530
Accounts payable and accrued expenses	15,278		(4,689)
CASH PROVIDED BY (USED IN) OPERATING ACTIVITIES	293,072		346,961
CASH FLOWS FROM INVESTING ACTIVITIES
Payments for fixed assets	24,540		27,489
Business acquisitions, net of cash acquired of $29,830	(2,950)		(1,009,928)
Payments to Acquire Assets, Investing Activities			0
Proceeds from Sales of Assets, Investing Activities	0		12,081
Contingent Payment Received, Investing Activities	2,561		0
Change in restricted cash	1,262		(4,849)
CASH PROVIDED BY (USED IN) INVESTING ACTIVITIES	(18,554)		(1,014,946)
CASH FLOWS FROM FINANCING ACTIVITIES
Payment for Contingent Consideration Liability, Financing Activities	(2,503)		(6,587)
Business Acquisition, Preacquisition Contingency, Amount of Settlement	(739)		0
Issuance of common stock for stock-based compensation	11,050		4,306
Employee Tax Withholdings by settlement of net share transaction	13,074		11,845
Repurchase of common stock	479,139		291,674
Dividends paid	76,000		66,178
Noncontrolling Interest, Decrease from Distributions to Noncontrolling Interest Holders	43,477		23,351
CASH PROVIDED BY (USED IN) FINANCING ACTIVITIES	(332,935)		28,722
Consolidated Entity Excluding Consolidated Investment Vehicles Before Eliminations [Member]
Income Taxes Paid, Net	16,770		14,436
Adjustments to reconcile Net Income to net cash used in operations:
Unrealized Gain (Loss) on Investments	(21,841)		(25,633)
Net (gains) losses on investments	2,874		(959)
Decrease (increase) in assets:
Other assets	(2,199)		13,070
Increase (decrease) in liabilities:
Other liabilities	(24,853)		(74,896)
CASH FLOWS FROM INVESTING ACTIVITIES
Cash Acquired	33,547
Proceeds from sales and maturities of investment securities	7,637		5,541
CASH FLOWS FROM FINANCING ACTIVITIES
Proceeds from Lines of Credit	225,500		(40,000)
Debt issuance costs	0		17,639
Proceeds from Issuance of Long-term Debt	0		500,000
EFFECT OF EXCHANGE RATES ON CASH	5,030		(357)
NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS	(53,387)		(639,620)
CASH AND CASH EQUIVALENTS AT BEGINNING OF YEAR	733,709		1,329,126
CASH AND CASH EQUIVALENTS AT END OF YEAR	680,322		689,506
Interest Paid	67,482		59,601
Proceeds from Income Tax Refunds	(9,505)		(754)
Consolidated Investment Vehicles [Member]
Adjustments to reconcile Net Income to net cash used in operations:
Net (gains) losses on investments	11,316		9,892
Decrease (increase) in assets:
Other assets	54,648		(17,530)
Increase (decrease) in liabilities:
Other liabilities	(249)		(2,489)
CASH FLOWS FROM FINANCING ACTIVITIES
Proceeds from (Payments to) Noncontrolling Interests	44,708		(18,310)
CASH AND CASH EQUIVALENTS AT BEGINNING OF YEAR	651
CASH AND CASH EQUIVALENTS AT END OF YEAR	4,325
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	(15,811)		(39,500)
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	47,401	[1],[2]	(20,914)	[1],[2]
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
Domestic Tax Authority [Member]
Adjustments to reconcile Net Income to net cash used in operations:
Effective Income Tax Rate Reconciliation, Change in Deferred Tax Assets Valuation Allowance, Amount	$ (213,675)		$ 0

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

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