Investments and Fair Values of Assets and Liabilities (Details 3) (Legg Mason, Inc., USD $) In Thousands, unless otherwise specified	3 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013 Trading proprietary fund products and other investments	Jun. 30, 2012 Equity method investments in proprietary fund products	Jun. 30, 2013 Investments in partnerships, LLCs and other	Jun. 30, 2012 Investments in partnerships, LLCs and other	Jun. 30, 2013 Equity method investments in partnerships and LLCs	Jun. 30, 2012 Equity method investments in partnerships and LLCs	Jun. 30, 2013 Other Investments	Jun. 30, 2012 Other Investments	Jun. 30, 2013 Contingent consideration liability	Mar. 31, 2013 Contingent consideration liability
Fair Value Assets and Liabilities Measured on Recurring Basis Financial Statement Unobservable Input Level 3
Assets measured at fair value using significant unobservable inputs, value at beginning of period	$ 94,457	$ 207,103	$ 246	$ 11,778	$ 27,762	$ 28,763	$ 66,338	$ 166,438	$ 111	$ 124
Fair Value, Measurement with Unobservable Inputs Reconciliations, Recurring Basis, Liability Value											21,931	21,900
Purchases	996	90	0	0	800	0	196	90	0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Purchases											0
Sales	(506)	(1,602)	0	0	(193)	0	(313)	(1,602)	0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Sales											0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements	(3,750)	(5,765)	(13)	0	(165)	(151)	(3,572)	(5,614)	0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Settlements											0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Transfers, Net											0
Transfers, Net	0	0	0	0	0	0	0	0	0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Period Increase (Decrease)	512	713	0	(482)	(186)	(99)	704	1,290	(6)	4
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Period Increase (Decrease)											31
Assets measured at fair value using significant unobservable inputs, value at end of period	91,709	200,539	233	11,296	28,018	28,513	63,353	160,602	105	128
Unrealized gains (losses) on Level 3 assets and liabilities still held at the reporting date	$ (793)	$ 1,284