Noncontrolling Interests Rollforward (Details) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Mar. 31, 2017	May 02, 2016	Mar. 31, 2016
Noncontrolling Interest [Line Items]
Redeemable Noncontrolling Interest, Equity, Carrying Amount		$ 727,706	$ 696,800	$ 727,706	$ 696,800	$ 677,772		$ 175,785
Net Income (Loss) Attributable to Redeemable Noncontrolling Interest		17,228	11,063	37,514	39,335
Proceeds from (Payments to) Noncontrolling Interests				44,708	(18,310)
Noncontrolling Interest, Decrease from Distributions to Noncontrolling Interest Holders				(36,953)	(18,797)
Business Combination, Acquisition of Less than 100 Percent, Noncontrolling Interest, Fair Value			510,500		510,500
Noncontrolling Interest, Period Increase (Decrease), Foreign Exchange				1,500	(4,094)
RE Reclassified for MEP Amortization				3,165	6,261
CIVs and Other
Noncontrolling Interest [Line Items]
Redeemable Noncontrolling Interest, Equity, Carrying Amount	[1]	113,794	81,375	113,794	81,375	58,470		94,136
Net Income (Loss) Attributable to Redeemable Noncontrolling Interest	[1]			7,923	8,153
Proceeds from (Payments to) Noncontrolling Interests	[1],[2]			47,401	(20,914)
Noncontrolling Interest, Decrease from Distributions to Noncontrolling Interest Holders				0	0
RE Reclassified for MEP Amortization	[1]			0	0
Noncontrolling Interest [Member]
Noncontrolling Interest [Line Items]
Redeemable Noncontrolling Interest, Equity, Carrying Amount		583,442	590,317	583,442	590,317	591,254		68,922
Net Income (Loss) Attributable to Redeemable Noncontrolling Interest				29,591	31,182
Proceeds from (Payments to) Noncontrolling Interests		(2,693)		(2,693)	2,604
Noncontrolling Interest, Decrease from Distributions to Noncontrolling Interest Holders				(36,953)	18,797
Business Combination, Acquisition of Less than 100 Percent, Noncontrolling Interest, Fair Value			510,500		510,500
Noncontrolling Interest, Period Increase (Decrease), Foreign Exchange				1,500	(4,094)
RE Reclassified for MEP Amortization					0
Noncontrolling Interest, Change in Redemption Value				743
Management Equity Plan [Member]
Noncontrolling Interest [Line Items]
Redeemable Noncontrolling Interest, Equity, Carrying Amount		30,470	25,108	30,470	25,108	28,048		12,727
Net Income (Loss) Attributable to Redeemable Noncontrolling Interest				0	0
Proceeds from (Payments to) Noncontrolling Interests					6,120
Noncontrolling Interest, Decrease from Distributions to Noncontrolling Interest Holders				0	0
RE Reclassified for MEP Amortization				2,422	6,261
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		398,107	407,444	398,107	407,444	404,852		0
Net Income (Loss) Attributable to Redeemable Noncontrolling Interest				17,014	17,099
Proceeds from (Payments to) Noncontrolling Interests		0			0
Noncontrolling Interest, Decrease from Distributions to Noncontrolling Interest Holders				(23,759)	12,855
Business Combination, Acquisition of Less than 100 Percent, Noncontrolling Interest, Fair Value			403,200		403,200
Noncontrolling Interest, Period Increase (Decrease), Foreign Exchange				0	0
Noncontrolling Interest, Change in Redemption Value				0
Clarion Partners [Member] | Noncontrolling Interest [Member]
Noncontrolling Interest [Line Items]
Redeemable Noncontrolling Interest, Equity, Carrying Amount		114,179	111,406	114,179	111,406	113,173		0
Net Income (Loss) Attributable to Redeemable Noncontrolling Interest				9,725	8,839
Proceeds from (Payments to) Noncontrolling Interests		0			0
Noncontrolling Interest, Decrease from Distributions to Noncontrolling Interest Holders				(9,462)	2,733
Business Combination, Acquisition of Less than 100 Percent, Noncontrolling Interest, Fair Value			105,300		105,300
Noncontrolling Interest, Period Increase (Decrease), Foreign Exchange				0	0
Noncontrolling Interest, Change in Redemption Value				743
RARE Infrastructure, Ltd [Member] | Noncontrolling Interest [Member]
Noncontrolling Interest [Line Items]
Redeemable Noncontrolling Interest, Equity, Carrying Amount		69,598	65,089	69,598	65,089	68,747		67,155
Net Income (Loss) Attributable to Redeemable Noncontrolling Interest				2,948	4,731
Proceeds from (Payments to) Noncontrolling Interests		0			0
Noncontrolling Interest, Decrease from Distributions to Noncontrolling Interest Holders				(3,597)	2,703
Business Combination, Acquisition of Less than 100 Percent, Noncontrolling Interest, Fair Value			0		0
Noncontrolling Interest, Period Increase (Decrease), Foreign Exchange				1,500	(4,094)
Noncontrolling Interest, Change in Redemption Value				0
Royce [Member]
Noncontrolling Interest [Line Items]
Net Income (Loss) Attributable to Nonredeemable Noncontrolling Interest		2,096	2,025	6,387	5,732
Management Equity Plan [Member] | Royce [Member]
Noncontrolling Interest [Line Items]
Net Income (Loss) Attributable to Nonredeemable Noncontrolling Interest				6,387	5,732
Noncontrolling Interest, Decrease from Distributions to Noncontrolling Interest Holders	[3]			(6,524)	(4,555)
Stockholders' Equity Attributable to Noncontrolling Interest	[3]	27,661	23,379	27,661	23,379	27,798		22,202
Other Affiliates [Member] | Noncontrolling Interest [Member]
Noncontrolling Interest [Line Items]
Redeemable Noncontrolling Interest, Equity, Carrying Amount		1,558	6,378	1,558	6,378	$ 4,482		$ 1,767
Net Income (Loss) Attributable to Redeemable Noncontrolling Interest				(96)	513
Proceeds from (Payments to) Noncontrolling Interests		$ (2,693)			2,604
Noncontrolling Interest, Decrease from Distributions to Noncontrolling Interest Holders				(135)	506
Business Combination, Acquisition of Less than 100 Percent, Noncontrolling Interest, Fair Value			$ 2,000		2,000
Noncontrolling Interest, Period Increase (Decrease), Foreign Exchange				0	$ 0
Noncontrolling Interest, Change in Redemption Value				$ 0

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

[2] (3) Includes the impact related to the adoption of updated consolidation accounting guidance.

[3] (2) Related to Royce management equity plan.