Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Other comprehensive income (loss):
Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss), Reclassification Adjustment from AOCI, before Tax	$ 121		$ 240
Consolidated Legg Mason, Inc.
NET INCOME	87,624	$ 86,532	151,161	$ 131,872
Other comprehensive income (loss):
Foreign currency translation adjustment	21,442	4,167	32,113	(13,023)
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Net of Tax	0	289	0	(2,718)
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Tax	0	(181)	0	1,708
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, Net of Tax	0	2,394	0	2,718
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, Tax	0	1,505	0	1,708
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Net of Tax	0	2,683	0	0
Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, before Tax	121	(14,054)	240	(19,159)
Total other comprehensive income (loss)	21,563	(7,204)	32,353	(32,182)
COMPREHENSIVE INCOME	109,187	79,328	183,514	99,690
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Noncontrolling Interest	10,483	18,152	22,767	32,038
COMPREHENSIVE INCOME ATTRIBUTABLE TO LEGG MASON, INC.	$ 98,704	$ 61,176	160,747	67,652
AOCI Attributable to Parent [Member] | Consolidated Legg Mason, Inc.
Other comprehensive income (loss):
Foreign currency translation adjustment			32,113
Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss) Arising During Period, before Tax			$ 240	$ (19,159)