Fair Values of Assets and Liabilities (Tables) - Consolidated Entity Excluding Consolidated Investment Vehicles Before Eliminations [Member]

9 Months Ended

Dec. 31, 2017

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Fair Value Measurements, Recurring and Nonrecurring [Table Text Block]



	As of December 31, 2017
	Quoted prices in active markets (Level 1)			Significant other observable inputs (Level 2)		Significant unobservable inputs (Level 3)			Investments measured at NAV		Total
Assets:
Cash equivalents:⁽¹⁾
Money market funds	$	289,214		$	—	$	—		$	—	$	289,214
Time deposits and other	—			12,317		—			—		12,317
Total cash equivalents	289,214			12,317		—			—		301,531
Trading investments of proprietary fund products and other trading investments:⁽²⁾
Seed capital investments	120,329			58,158		—			3,593		182,080
Other⁽³⁾	26,717			2,556		—			—		29,273
Trading investments relating to long-term incentive compensation plans⁽⁴⁾	187,473			—		—			103		187,576
Equity method investments relating to long-term incentive compensation plans⁽⁵⁾	—			—		1,431			9,009		10,440
Total current investments⁽⁶⁾	334,519			60,714		1,431			12,705		409,369
Equity method investments in partnerships and LLCs:⁽⁵⁾⁽⁷⁾
Seed capital investments⁽⁶⁾	—			—		891			15,595		16,486
Seed capital investments in real estate funds	—			—		27,837			—		27,837
Other	—			—		—			12,569		12,569
Investments in partnerships and LLCs:⁽⁷⁾
Seed capital investments	—			—		—			3,287		3,287
Investments related to long-term incentive compensation plans	—			—		9,367			—		9,367
Other	—			102		380			—		482
Derivative assets⁽⁷⁾⁽⁸⁾	7,183			—		—			—		7,183
Other investments⁽⁷⁾	—			—		112			—		112
Total	$	630,916		$	73,133	$	40,018		$	44,156	$	788,223
Liabilities:
Contingent consideration liabilities⁽⁹⁾	$	—		$	—	$	(20,701	)	$	—	$	(20,701	)
Derivative liabilities⁽⁸⁾	(2,288		)	—		—			—		(2,288		)
Total	$	(2,288	)	$	—	$	(20,701	)	$	—	$	(22,989	)



	As of March 31, 2017
	Quoted prices in active markets (Level 1)			Significant other observable inputs (Level 2)		Significant unobservable inputs (Level 3)			Investments measured at NAV		Total
Assets:
Cash equivalents:⁽¹⁾
Money market funds	$	403,585		$	—	$	—		$	—	$	403,585
Time deposits and other	—			35,835		—			—		35,835
Total cash equivalents	403,585			35,835		—			—		439,420
Trading investments of proprietary fund products and other trading investments:⁽²⁾
Seed capital investments	141,025			75,275		—			4,373		220,673
Other⁽³⁾	39,177			2,724		—			11		41,912
Trading investments relating to long-term incentive compensation plans⁽⁴⁾	150,576			—		—			327		150,903
Equity method investments relating to proprietary fund products and long-term incentive compensation plans:⁽⁵⁾
Seed capital investments	—			2,502		—			—		2,502
Investments related to long-term incentive compensation plans	—			—		1,337			6,292		7,629
Total current investments⁽⁶⁾	330,778			80,501		1,337			11,003		423,619
Equity method investments in partnerships and LLCs:⁽⁵⁾⁽⁷⁾
Seed capital investments⁽⁶⁾	—			—		752			22,712		23,464
Seed capital investments in real estate funds	—			—		26,909			—		26,909
Other	—			—		1,646			15,617		17,263
Investments in partnerships and LLCs:⁽⁷⁾
Seed capital investments	—			—		—			3,440		3,440
Investments related to long-term incentive compensation plans	—			—		9,315			—		9,315
Other	—			99		1,825			—		1,924
Derivative assets⁽⁷⁾⁽⁸⁾	2,718			—		—			—		2,718
Other investments⁽⁷⁾	—			—		113			—		113
Total	$	737,081		$	116,435	$	41,897		$	52,772	$	948,185
Liabilities:
Contingent consideration liabilities⁽⁹⁾	$	—		$	—	$	(36,810	)	$	—	$	(36,810	)
Derivative liabilities⁽⁸⁾	(4,522		)	—		—			—		(4,522		)
Total	$	(4,522	)	$	—	$	(36,810	)	$	—	$	(41,332	)

(1)

Cash equivalents include highly liquid investments with original maturities of 90 days or less. Cash investments in actively traded money market funds are classified as Level 1. Cash investments in time deposits and other are measured at amortized cost, which approximates fair value because of the short time between purchase of the instrument and its expected realization, and are classified as Level 2.


(2)	Trading investments of proprietary fund products and other trading investments consist of approximately 77% and 23% equity and debt securities, respectively, as of December 31, 2017, and approximately 79% and 21% equity and debt securities, respectively, as of March 31, 2017.


(3)	Includes $13,696 and $26,854 in noncontrolling interests associated with consolidated seed investment products as of December 31, 2017 and March 31, 2017, respectively.


(4)	Primarily mutual funds where there is minimal market risk to the Company as any change in value is primarily offset by an adjustment to compensation expense and related deferred compensation liability.

(5)

Certain of Legg Mason's equity method investments are investment companies that record underlying investments at fair value. Therefore, the fair value of these investments is measured using Legg Mason's share of the investee's underlying net income or loss, which is predominately representative of fair value adjustments in the investments held by the equity method investee. Other equity method investments not measured at fair value on a recurring basis are excluded from the tables above.


(6)	Excludes $41,548 and $28,300 of seed capital as of December 31, 2017 and March 31, 2017, respectively, which is related to Legg Mason's investments in CIVs. See Note 13.


(7)	Amounts are included in Other non-current assets in the Consolidated Balance Sheets for each of the periods presented.


(8)	See Note 12.


(9)	See Notes 3 and 9.

Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Table Text Block]



	Balance as of September 30, 2017			Purchases			Sales		Redemptions/ Settlements/ Other			Transfers		Realized and unrealized gains/(losses), net			Balance as of December 31, 2017
Assets:
Equity method investments relating to long-term incentive compensation plans	$	1,393		$	11		$	—	$	(11	)	$	—	$	38		$	1,431
Equity method investments in partnerships and LLCs:
Seed capital investments	851			—			—		—			—		40			891
Seed capital investments in real estate funds	27,382			868			—		(1,139		)	—		726			27,837
Investments in partnerships and LLCs:
Investments related to long-term incentive compensation plans	9,367			—			—		—			—		—			9,367
Other proprietary fund products	485			—			—		(105		)	—		—			380
Other investments	114			—			—		—			—		(2		)	112
	$	39,592		$	879		$	—	$	(1,255	)	$	—	$	802		$	40,018
Liabilities:
Contingent consideration liabilities	$	(21,162	)	$	(1,900	)	n/a		$	3,242		n/a		$	(881	)	$	(20,701	)

n/a - not applicable



	Balance as of September 30, 2016			Purchases		Sales		Redemptions/ Settlements/ Other			Transfers		Realized and unrealized gains/(losses), net			Balance as of December 31, 2016
Assets:
Equity method investments relating to long-term incentive compensation plans	$	2,653		$	20	$	—	$	(20	)	$	—	$	48		$	2,701
Equity method investments in partnerships and LLCs:
Seed capital investments	552			—		—		—			—		39			591
Seed capital investments in real estate funds	25,722			667		—		(197		)	—		487			26,679
Investments in partnerships and LLCs:
Investments related to long-term incentive compensation plans	7,501			314		—		—			—		—			7,815
Other proprietary fund products	3,827			—		—		(2,000		)	—		541			2,368
Other investments	245			—		—		—			—		(83		)	162
	$	40,500		$	1,001	$	—	$	(2,217	)	$	—	$	1,032		$	40,316
Liabilities:
Contingent consideration liabilities	$	(52,053	)	$	—	n/a		$	—		n/a		$	16,569		$	(35,484	)

n/a - not applicable



	Balance as of March 31, 2017			Purchases			Sales		Redemptions/ Settlements/ Other			Transfers		Realized and unrealized gains/(losses), net			Balance as of December 31, 2017
Assets:
Equity method investments relating to long-term incentive compensation plans	$	1,337		$	33		$	—	$	(33	)	$	—	$	94		$	1,431
Equity method investments in partnerships and LLCs:
Seed capital investments	752			—			—		—			—		139			891
Seed capital investments in real estate funds	26,909			3,063			—		(3,889		)	—		1,754			27,837
Other proprietary fund products	1,646			—			—		(1,646		)	—		—			—
Investments in partnerships and LLCs:
Investments related to long-term incentive compensation plans	9,315			52			—		—			—		—			9,367
Other proprietary fund products	1,825			—			—		(1,510		)	—		65			380
Other investments	113			—			—		—			—		(1		)	112
	$	41,897		$	3,148		$	—	$	(7,078	)	$	—	$	2,051		$	40,018
Liabilities:
Contingent consideration liabilities	$	(36,810	)	$	(1,900	)	n/a		$	3,242		n/a		$	14,767		$	(20,701	)

n/a - not applicable



	Balance as of March 31, 2016			Purchases			Sales		Redemptions/Settlements/ Other			Transfers		Realized and unrealized gains/(losses), net			Balance as of December 31, 2016
Assets:
Trading investments of seed capital investments in proprietary fund products	$	3		$	—		$	—	$	(3	)	$	—	$	—		$	—
Equity method investments relating to long-term incentive compensation plans	—			2,979			—		(448		)	—		170			2,701
Equity method investments in partnerships and LLCs:
Seed capital investments	627			—			—		—			—		(36		)	591
Seed capital investments in real estate funds	—			25,966			—		(636		)	—		1,349			26,679
Investments in partnerships and LLCs:
Investments related to long-term incentive compensation plans	7,501			314			—		—			—		—			7,815
Other proprietary fund products	4,807			—			—		(3,000		)	—		561			2,368
Other investments	83			—			—		—			—		79			162
	$	13,021		$	29,259		$	—	$	(4,087	)	$	—	$	2,123		$	40,316
Liabilities:
Contingent consideration liabilities	$	(84,585	)	$	(2,000	)	n/a		$	6,587		n/a		$	44,514		$	(35,484	)

Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Table Text Block]



		Fair Value Determined Using NAV					As of December 31, 2017
Category of Investment	Investment Strategy	December 31, 2017			March 31, 2017		Unfunded Commitments		Remaining Term
Funds-of-hedge funds	Global macro, fixed income, long/short equity, natural resources, systematic, emerging market, European hedge	$	11,024	(1)	$	18,537	n/a		n/a
Hedge funds	Fixed income - developed market, event driven, fixed income - hedge, relative value arbitrage, European hedge	9,760			10,107		$	20,000	n/a
Private equity funds	Long/short equity	14,231		(2)	17,612		6,589		Up to 11 years
Equity method	Long/short fixed income	9,009			6,292		n/a		n/a
Other	Various	132			224		n/a		Various ⁽³⁾
Total		$	44,156		$	52,772	$	26,589

n/a - not applicable


(1)	Liquidation restrictions: 1% daily redemption, 20% monthly redemption, 11% quarterly redemption, and 68% are not subject to redemption or are not currently redeemable.


(2)	Liquidations are expected over the remaining term.


(3)	Of this balance, 34% has a remaining term of less than one year and 66% has a remaining term of 14 years.

- Definition

Tabular disclosure of financial instruments measured at fair value, including those classified in shareholders' equity measured on a recurring or nonrecurring basis. Disclosures include, but are not limited to, fair value measurements recorded and the reasons for the measurements, level within the fair value hierarchy in which the fair value measurements are categorized and transfers between levels 1 and 2. Nonrecurring fair value measurements are those that are required or permitted in the statement of financial position in particular circumstances.

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