Fair Values of Assets and Liabilities (Details 3) (USD $)	12 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Assets measured at fair value using significant unobservable inputs, value at beginning of period	$ 94,457,000	$ 207,103,000
Purchases	5,155,000	3,073,000
Sales	(1,493,000)	(3,238,000)
Redemptions/Settlements/Other	(14,204,000)	(130,130,000)
Transfers, Net	0	0
Realized and unrealized gains/(losses), net	924,000	17,649,000
Assets measured at fair value using significant unobservable inputs, value at end of period	84,839,000	94,457,000
Unrealized Gains (Losses) Relating to Fair Value Measurements Using Unobservable Inputs Assets and Liabilities Still Held at Reporting Date	(5,210,000)	(1,229,000)
Legg Mason, Inc
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value, Assets, Level 1 to Level 2 Transfers, Amount	0	0
Fair Value, Assets, Level 2 to Level 1 Transfers, Amount	0	0
Fair Value, Liabilities, Level 1 to Level 2 Transfers, Amount	0	0
Fair Value, Liabilities, Level 2 to Level 1 Transfers, Amount	0	0
Other Investments [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Assets measured at fair value using significant unobservable inputs, value at beginning of period	111,000	124,000
Purchases	0	0
Sales	(12,000)	0
Redemptions/Settlements/Other	0	0
Transfers, Net	0	0
Realized and unrealized gains/(losses), net	(9,000)	(13,000)
Assets measured at fair value using significant unobservable inputs, value at end of period	90,000	111,000
Proprietary Fund Product And Other Investments [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Assets measured at fair value using significant unobservable inputs, value at beginning of period	246,000	0
Purchases	1,000	246,000
Sales	0	0
Redemptions/Settlements/Other	(77,000)	0
Transfers, Net	0	0
Realized and unrealized gains/(losses), net	20,000	0
Assets measured at fair value using significant unobservable inputs, value at end of period	190,000	246,000
Equity Method Investments In Proprietary Fund Products [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Assets measured at fair value using significant unobservable inputs, value at beginning of period		11,778,000
Purchases		0
Sales		0
Redemptions/Settlements/Other		(11,705,000)
Transfers, Net		0
Realized and unrealized gains/(losses), net		(73,000)
Assets measured at fair value using significant unobservable inputs, value at end of period		0
Investment In Partnerships And Limited Liability Companies [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Assets measured at fair value using significant unobservable inputs, value at beginning of period	27,762,000	28,763,000
Purchases	0	0
Sales	(731,000)	(970,000)
Redemptions/Settlements/Other	(4,869,000)	(1,014,000)
Transfers, Net	0	0
Realized and unrealized gains/(losses), net	(576,000)	983,000
Assets measured at fair value using significant unobservable inputs, value at end of period	21,586,000	27,762,000
Equity Method Investments In Partnerships And LLCs [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Assets measured at fair value using significant unobservable inputs, value at beginning of period	66,338,000	166,438,000
Purchases	5,154,000	2,827,000
Sales	(750,000)	(2,268,000)
Redemptions/Settlements/Other	(9,258,000)	(117,411,000)
Transfers, Net	0	0
Realized and unrealized gains/(losses), net	1,489,000	16,752,000
Assets measured at fair value using significant unobservable inputs, value at end of period	62,973,000	66,338,000
Contingent Consideration Liability [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Liabilities measured at fair value using significant unobservable inputs, value at beginning of period	(21,900,000)	0
Purchases	0	(21,566,000)
Sales	0	0
Redemptions/Settlements/Other	0	0
Transfers, Net	0	0
Realized and unrealized gains/(losses), net	(7,653,000)	(334,000)
Liabilities measured at fair value using significant unobservable inputs, value at end of period	$ (29,553,000)	$ (21,900,000)