Investments and Fair Values of Assets and Liabilities (Details 1) (Legg Mason, Inc., USD $) In Thousands, unless otherwise specified	3 Months Ended
	Jun. 30, 2013		Mar. 31, 2013		Mar. 31, 2012
Quoted prices in active markets (Level 1)
Cash equivalents:
Money market funds	$ 347,063		$ 485,776
Time deposits	0		0
Total cash equivalents	347,063		485,776
Investment Securities
Trading investments relating to long-term incentive compensation plans	106,734		86,583
Trading proprietary fund products and other investments	184,578		158,846
Equity method investments relating to long-term incentive compensation plans, proprietary fund products and other investments	11,939		12,600
Total current investments	303,251		258,029
Available-for-sale investment securities	2,033		2,034
Investments in partnerships, LLCs and other	679		761
Equity method investments in partnerships and LLCs	1,533		1,518
Derivative Assets:
Currency and market hedges	3,900		1,939
Other investments	0		0
Financial assets measured at fair value	658,459		750,057
Liabilities
Business Acquisition, Contingent Consideration, Potential Cash Payment	0		0
Derivative liabilities:
Currency and market hedges	(1,794)		(781)
Liabilities, Fair Value Disclosure	(1,794)		(781)
Significant other observable inputs (Level 2)
Cash equivalents:
Money market funds	0		0
Time deposits	108,754		177,471
Total cash equivalents	108,754		177,471
Investment Securities
Trading investments relating to long-term incentive compensation plans	0		0
Trading proprietary fund products and other investments	67,302		69,064
Equity method investments relating to long-term incentive compensation plans, proprietary fund products and other investments	16,881		43,741
Total current investments	84,183		112,805
Available-for-sale investment securities	9,960		10,354
Investments in partnerships, LLCs and other	2,731		2,620
Equity method investments in partnerships and LLCs	797		924
Derivative Assets:
Currency and market hedges	0		0
Other investments	0		0
Financial assets measured at fair value	206,425		304,174
Liabilities
Business Acquisition, Contingent Consideration, Potential Cash Payment	0		0
Derivative liabilities:
Currency and market hedges	0		0
Liabilities, Fair Value Disclosure	0		0
Significant unobservable inputs (Level 3)
Cash equivalents:
Money market funds	0		0
Time deposits	0		0
Total cash equivalents	0		0
Investment Securities
Trading investments relating to long-term incentive compensation plans	0		0
Trading proprietary fund products and other investments	233		246
Equity method investments relating to long-term incentive compensation plans, proprietary fund products and other investments	0		0
Total current investments	233		246
Available-for-sale investment securities	12		12
Investments in partnerships, LLCs and other	28,018		27,762
Equity method investments in partnerships and LLCs	63,353		66,338
Derivative Assets:
Currency and market hedges	0		0
Other investments	93		99
Financial assets measured at fair value	91,709		94,457
Liabilities
Business Acquisition, Contingent Consideration, Potential Cash Payment	(21,931)		(21,900)
Derivative liabilities:
Currency and market hedges	0		0
Liabilities, Fair Value Disclosure	(21,931)		(21,900)
Total
Cash equivalents:
Money market funds	347,063	[1]	485,776	[1]
Time deposits	108,754	[1]	177,471	[1]
Total cash equivalents	455,817	[1]	663,247	[1]
Investment Securities
Trading investments relating to long-term incentive compensation plans	106,734	[2]	86,583	[2]
Trading proprietary fund products and other investments	252,113	[3]	228,156	[3]
Equity method investments relating to long-term incentive compensation plans, proprietary fund products and other investments	28,820	[4],[5]	56,341	[4],[5]
Total current investments	387,667		371,080
Available-for-sale investment securities	12,005	[6]	12,400	[6]
Investments in partnerships, LLCs and other	31,428	[6]	31,143	[6]
Equity method investments in partnerships and LLCs	65,683	[5],[6]	68,780	[5],[6]
Derivative Assets:
Currency and market hedges	3,900		1,939
Other investments	93	[6]	99	[6]
Financial assets measured at fair value	956,593		1,148,688
Liabilities
Business Acquisition, Contingent Consideration, Potential Cash Payment	(21,931)		(21,900)
Derivative liabilities:
Currency and market hedges	(1,794)		(781)
Liabilities, Fair Value Disclosure	(23,725)		(22,681)
Cash and Cash Equivalents, Maturity Period	90
Proprietary fund products disclosures
Proprietary fund products and other investments, equity securities percentage (as a percent)	62.00%		49.00%		52.00%
Proprietary fund products and other investments, debt securities percentage (as a percent)	38.00%		51.00%		48.00%
Equity method investments relating to long-term incentive compensation plans	16,881		43,741
Equity method investments relating to proprietary fund products and other investments	$ 11,939		$ 12,600

[1] Cash equivalents include highly liquid investments with original maturities of 90 days or less. Cash investments in actively traded money market funds are measured at net asset value ("NAV") and 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 the purchase of the instrument and its expected realization, and are classified as Level 2.

[2] 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.

[3] Trading proprietary fund products and other investments primarily represent mutual funds that are invested approximately 62% and 38% in equity and debt securities, respectively, as of June 30, 2013, and were invested approximately 49% and 51% in equity and debt securities, respectively, as of March 31, 2013.

[4] Includes investments under the equity method (which approximates fair value) relating to long-term incentive compensation plans of $16,881 and $43,741 as of June 30, 2013 and March 31, 2013, respectively, and proprietary fund products and other investments of $11,939 and $12,600 as of June 30, 2013 and March 31, 2013, respectively, which are classified as Investment securities on the Consolidated Balance Sheets.

[5] Substantially all of Legg Mason's equity method investments are investment companies which record their underlying investments at fair value. Fair value 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.

[6] Amounts are included in Other non-current assets on the Consolidated Balance Sheets for each of the periods presented.