Earnings Per Share Schedule of Basic and Diluted EPS (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Jun. 30, 2016	Jun. 30, 2015
Consolidated Legg Mason, Inc.
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Weighted Average Number of Shares Outstanding, Basic	104,465	108,954
Incremental Common Shares Attributable to Dilutive Effect of Share-based Payment Arrangements	212	1,281
Weighted Average Number of Shares Outstanding, Diluted	104,677	110,235
Net Income Attributable to Legg Mason, Inc.	$ 33,452	$ 94,548
Basic (in dollars per share)	$ 0.31	$ 0.85
Earnings Per Share, Diluted	$ 0.31	$ 0.84
Consolidated Entity Excluding Consolidated Investment Vehicles Before Eliminations [Member]
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Net Income Attributable to Legg Mason, Inc.	$ 33,452	$ 94,548
Participating Securities, Distributed and Undistributed Earnings (Loss), Diluted	1,051	2,327
Net Income (Loss) Available to Common Stockholders, Diluted	$ 32,401	$ 92,221
Restricted Stock [Member]
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Incremental Common Shares Attributable to Participating Nonvested Shares with Non-forfeitable Dividend Rights	3,134	2,737