Consolidated Statements of Income (Loss) (Consolidated Legg Mason [Domain], USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2012	Dec. 31, 2011
Consolidated Legg Mason [Domain]
Investment advisory fees
Separate accounts	$ 181,755	$ 187,570	$ 547,617	$ 588,382
Funds	360,827	351,598	1,080,208	1,128,577
Performance fees	46,395	6,079	65,240	34,677
Distribution and service fees	83,083	80,709	246,621	258,547
Other	1,840	1,022	5,201	3,800
Total operating revenues	673,900	626,978	1,944,887	2,013,983
Operating Expenses
Compensation and benefits	308,248	254,402	881,002	812,405
Transition-related compensation	0	8,818	0	32,559
Total compensation and benefits	308,248	263,220	881,002	844,964
Distribution and servicing	143,410	148,275	458,370	489,422
Communications and technology	38,400	43,466	111,861	125,538
Occupancy	31,072	56,401	88,642	125,339
Amortization of intangible assets	3,505	4,869	10,514	15,951
Impairment of intangible assets	734,000	0	734,000	0
Other	48,588	51,424	138,010	146,228
Total operating expenses	1,307,223	567,655	2,422,399	1,747,442
Operating Income	(633,323)	59,323	(477,512)	266,541
Other Non-Operating Income (Expense)
Interest income	1,646	2,577	5,300	8,614
Interest expense	(13,564)	(21,831)	(46,909)	(65,828)
Other income (expense), net, including $68,975 debt extinguishment loss in May 2012	9,926	255	(34,052)	(31,844)
Other non-operating income (loss) of consolidated investment vehicles, net	(3,449)	7,424	(6,080)	15,607
Total other non-operating income (expense)	(5,441)	(11,575)	(81,741)	(73,451)
Income (loss) before income tax provision (benefit)	(638,764)	47,748	(559,253)	193,090
Income Tax Expense (Benefit)	(180,214)	12,607	(168,814)	38,868
Net Income (Loss)	(458,550)	35,141	(390,439)	154,222
Less: Net income (loss) attributable to noncontrolling interests	(4,680)	7,009	(7,908)	9,474
Net Income (Loss) Attributable to Legg Mason, Inc.	$ (453,870)	$ 28,132	$ (382,531)	$ 144,748
Net Income (Loss) per Share Attributable to Legg Mason, Inc. Common Shareholders:
Basic (in dollars per share)	$ (3.45)	$ 0.20	$ (2.84)	$ 1.00
Diluted (in dollars per share)	$ (3.45)	$ 0.20	$ (2.84)	$ 1.00
Weighted Average Number of Shares Outstanding, Basic	131,534	140,053	134,770	144,363
Weighted Average Number of Shares Outstanding, Diluted	131,534	140,082	134,770	144,428
Dividends Declared per Share (in dollars per share)	$ 0.11	$ 0.08	$ 0.33	$ 0.24