Consolidated Balance Sheets - USD ($) $ in Thousands		12 Months Ended
		Mar. 31, 2018	Mar. 31, 2017
Receivables:
Fixed assets, net		$ 148,406	$ 159,662
Current Liabilities
REDEEMABLE NONCONTROLLING INTERESTS		732,295	677,772
STOCKHOLDERS' EQUITY
Employee stock trust		(11)
AOCI Including Portion Attributable to Noncontrolling Interest, before Tax		$ (55,182)	$ (106,784)
Common Stock, Par or Stated Value Per Share		$ 0.10	$ 0.10
Common Stock, Shares Authorized		500,000,000	500,000,000
Common Stock, Shares, Issued		84,606,408	107,011,664
Consolidated Entity Excluding Consolidated Investment Vehicles Before Eliminations [Member]
Current Assets
Cash and Cash Equivalents		$ 736,130	$ 733,709
Receivables:
Investment securities	[1]	399,370	423,619
Other current assets		65,010	74,102
Current Liabilities
Business Combination, Contingent Consideration, Liability, Current	[2]	5,607	36,810
Other current liabilities		200,557	117,863
Consolidated Investment Vehicles [Member]
Current Assets
Cash and Cash Equivalents		2,800	651
Receivables:
Investment securities		140,133	49,901
Other current assets		1,893	0
Other non-current assets		9,257	9,987
Current Liabilities
Other current liabilities		634	736
Consolidated Legg Mason, Inc.
Current Assets
Restricted cash		30,428	16,046
Receivables:
Investment advisory and related fees		475,594	433,192
Other receivables		77,024	70,527
Total Current Assets		1,928,382	1,801,747
Fixed assets, net		148,406	159,662
Intangible assets, net		3,797,659	4,034,380
Goodwill		1,932,355	1,924,889
Deferred income taxes		202,068	202,843
Other non-current assets		134,407	156,907
TOTAL ASSETS		8,152,534	8,290,415
Current Liabilities
Accrued compensation		476,061	486,679
Accounts Payable and Accrued Liabilities, Current		175,583	181,793
Line of Credit, Current		125,500	0
Business Combination, Contingent Consideration, Liability, Current		5,607	36,810
Total Current Liabilities		982,042	809,387
Deferred compensation		92,422	87,757
Deferred income taxes		139,787	329,229
Business Combination, Contingent Consideration, Liability, Noncurrent		1,900	14,494
Other non-current liabilities		130,142	138,737
Long-term Debt		2,221,810	2,221,867
TOTAL LIABILITIES		3,568,103	3,601,471
REDEEMABLE NONCONTROLLING INTERESTS		732,295	677,772
STOCKHOLDERS' EQUITY
Common stock, par value $.10; authorized 500,000,000 shares; issued 84,606,408 shares in March 2018 and 95,726,628 shares in March 2017		8,461	9,573
Additional paid-in capital		1,976,364	2,385,726
Employee stock trust		(21,996)	(24,057)
Deferred compensation employee stock trust		21,996	24,057
Retained earnings		1,894,762	1,694,859
AOCI Including Portion Attributable to Noncontrolling Interest, before Tax		(55,182)	(106,784)
TOTAL STOCKHOLDERS' EQUITY		3,852,136	4,011,172
Stockholders' Equity Attributable to Parent		3,824,405	3,983,374
TOTAL LIABILITIES AND STOCKHOLDERS' EQUITY		8,152,534	8,290,415
ClearBridge Investments [Member]
Deferred Compensation Arrangement with Individual, Fair Value of Shares Issued		47,897
Management Equity Plan [Member]
Deferred Compensation Arrangement with Individual, Fair Value of Shares Issued		89,428
Management Equity Plan [Member] | Clarion Partners [Member]
Deferred Compensation Arrangement with Individual, Fair Value of Shares Issued		13,800
Management Equity Plan [Member] | Royce [Member]
STOCKHOLDERS' EQUITY
Stockholders' Equity Attributable to Noncontrolling Interest	[3]	27,731	27,798
Management Equity Plan [Member] | ClearBridge Investments [Member]
STOCKHOLDERS' EQUITY
Stockholders' Equity Attributable to Noncontrolling Interest	[3]	3,103	3,285
Martin Currie [Member]
Current Liabilities
Business Combination, Contingent Consideration, Liability, Current		0	12,018
Business Combination, Contingent Consideration, Liability, Noncurrent		0
Fair Value, Inputs, Level 3 [Member] | Consolidated Entity Excluding Consolidated Investment Vehicles Before Eliminations [Member]
Receivables:
Investment securities	[1]	1,242	1,337
Current Liabilities
Business Combination, Contingent Consideration, Liability, Current	[2]	$ 5,607	$ 36,810

[1] Excludes $43,854 and $28,300 of seed capital as of March 31, 2018 and 2017, respectively, which is related to Legg Mason's investments in CIVs. See Note 17.

[2] See Notes 2 and 8.

[3] 1) Principally related to VIE and seeded investment products.(2) Related to Royce management equity plan.(3) Includes the impact related to the adoption of updated consolidation accounting guidance further discussed in Note 1.