Noncontrolling Interests Rollforward (Details) - USD ($) $ in Thousands		12 Months Ended
		Mar. 31, 2017		Mar. 31, 2016		Mar. 31, 2015	May 02, 2016	Mar. 31, 2014
Noncontrolling Interest [Line Items]
Redeemable Noncontrolling Interest, Equity, Carrying Amount		$ 677,772		$ 175,785		$ 45,520		$ 45,144
Net Income (Loss) Attributable to Redeemable Noncontrolling Interest		52,050		(8,680)		5,629
Net Income (Loss) Attributable to Nonredeemable Noncontrolling Interest						0
Proceeds from (Payments to) Noncontrolling Interests		(44,587)		66,658		(10,459)
Noncontrolling Interest, Decrease from Distributions to Noncontrolling Interest Holders		(29,461)
Business Combination, Acquisition of Less than 100 Percent, Noncontrolling Interest, Fair Value		508,817		62,722
Noncontrolling Interest, Period Increase (Decrease), Foreign Exchange		(153)		3,860
RE Reclassified for MEP Amortization		9,335		6,050		5,206
CIVs and Other
Noncontrolling Interest [Line Items]
Redeemable Noncontrolling Interest, Equity, Carrying Amount	[1]	58,470		94,136		36,549		41,972
Net Income (Loss) Attributable to Redeemable Noncontrolling Interest	[1]	11,452		(11,052)		5,061
Proceeds from (Payments to) Noncontrolling Interests	[1]	(47,118)	[2]	68,639		(10,484)
Noncontrolling Interest, Decrease from Distributions to Noncontrolling Interest Holders		0
RE Reclassified for MEP Amortization	[1]	0		0		0
Noncontrolling Interest [Member]
Noncontrolling Interest [Line Items]
Redeemable Noncontrolling Interest, Equity, Carrying Amount		591,254		68,922		1,949		1,356
Net Income (Loss) Attributable to Redeemable Noncontrolling Interest		40,598		2,372		568
Proceeds from (Payments to) Noncontrolling Interests		2,531		(1,981)		25
Noncontrolling Interest, Decrease from Distributions to Noncontrolling Interest Holders		(29,461)		1,981
Business Combination, Acquisition of Less than 100 Percent, Noncontrolling Interest, Fair Value		508,817		62,722
Noncontrolling Interest, Period Increase (Decrease), Foreign Exchange		(153)		3,860
RE Reclassified for MEP Amortization		0		0		0
Management Equity Plan [Member]
Noncontrolling Interest [Line Items]
Redeemable Noncontrolling Interest, Equity, Carrying Amount		28,048		12,727		7,022		1,816
Net Income (Loss) Attributable to Redeemable Noncontrolling Interest		0		0		0
Proceeds from (Payments to) Noncontrolling Interests		5,986		(345)		0
Noncontrolling Interest, Decrease from Distributions to Noncontrolling Interest Holders		0
RE Reclassified for MEP Amortization		9,335		6,050		5,206
EnTrustPermal [Member]
Noncontrolling Interest [Line Items]
Business Combination, Acquisition of Less than 100 Percent, Noncontrolling Interest, Fair Value							$ 403,200
EnTrustPermal [Member] | Noncontrolling Interest [Member]
Noncontrolling Interest [Line Items]
Redeemable Noncontrolling Interest, Equity, Carrying Amount		404,852		0
Net Income (Loss) Attributable to Redeemable Noncontrolling Interest		22,146
Proceeds from (Payments to) Noncontrolling Interests		0
Noncontrolling Interest, Decrease from Distributions to Noncontrolling Interest Holders		(20,494)
Business Combination, Acquisition of Less than 100 Percent, Noncontrolling Interest, Fair Value		403,200
Noncontrolling Interest, Period Increase (Decrease), Foreign Exchange		0
Clarion Partners [Member] | Noncontrolling Interest [Member]
Noncontrolling Interest [Line Items]
Redeemable Noncontrolling Interest, Equity, Carrying Amount		113,173		0
Net Income (Loss) Attributable to Redeemable Noncontrolling Interest		12,171
Proceeds from (Payments to) Noncontrolling Interests		0
Noncontrolling Interest, Decrease from Distributions to Noncontrolling Interest Holders		(4,298)
Business Combination, Acquisition of Less than 100 Percent, Noncontrolling Interest, Fair Value		105,300
Noncontrolling Interest, Period Increase (Decrease), Foreign Exchange		0
RARE Infrastructure, Ltd [Member] | Noncontrolling Interest [Member]
Noncontrolling Interest [Line Items]
Redeemable Noncontrolling Interest, Equity, Carrying Amount		68,747		67,155		0
Net Income (Loss) Attributable to Redeemable Noncontrolling Interest		5,742		1,859
Proceeds from (Payments to) Noncontrolling Interests		0
Noncontrolling Interest, Decrease from Distributions to Noncontrolling Interest Holders		(3,997)		(1,286)
Business Combination, Acquisition of Less than 100 Percent, Noncontrolling Interest, Fair Value		0		62,722
Noncontrolling Interest, Period Increase (Decrease), Foreign Exchange		(153)		3,860
Royce [Member]
Noncontrolling Interest [Line Items]
Net Income (Loss) Attributable to Nonredeemable Noncontrolling Interest		7,397		802
Proceeds from (Payments to) Noncontrolling Interests	[3]			21,400
Stockholders' Equity Attributable to Noncontrolling Interest	[3]					0
Management Equity Plan [Member] | Royce [Member]
Noncontrolling Interest [Line Items]
Net Income (Loss) Attributable to Nonredeemable Noncontrolling Interest		7,397		802		0
Proceeds from (Payments to) Noncontrolling Interests	[3]	(4,600)
Noncontrolling Interest, Decrease from Distributions to Noncontrolling Interest Holders		(6,401)	[3]	0		0
Stockholders' Equity Attributable to Noncontrolling Interest		27,798	[3]	22,202	[3]	0		$ 0
Other Affiliates [Member] | Noncontrolling Interest [Member]
Noncontrolling Interest [Line Items]
Redeemable Noncontrolling Interest, Equity, Carrying Amount		4,482		1,767		$ 1,949
Net Income (Loss) Attributable to Redeemable Noncontrolling Interest		539		513
Proceeds from (Payments to) Noncontrolling Interests		2,531
Noncontrolling Interest, Decrease from Distributions to Noncontrolling Interest Holders		(672)		(695)
Business Combination, Acquisition of Less than 100 Percent, Noncontrolling Interest, Fair Value		317		0
Noncontrolling Interest, Period Increase (Decrease), Foreign Exchange		$ 0		$ 0

[1] Principally related to VIE and seeded investment products.

[2] Includes the impact related to the adoption of updated consolidation accounting guidance further discussed in Note 1.

[3] Related to Royce management equity plan.