Noncontrolling Interests Noncontrolling Interest Rollforward, By Affiliate (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Mar. 31, 2017	May 02, 2016	Mar. 31, 2016
Noncontrolling Interest [Line Items]
Proceeds from (Payments to) Noncontrolling Interests			$ 19,624	$ (39,469)
Redeemable Noncontrolling Interest, Equity, Carrying Amount	$ 698,774	$ 676,164	698,774	676,164	$ 677,772		$ 175,785
Net Income (Loss) Attributable to Redeemable Noncontrolling Interest	9,930	18,235	20,286	28,272
Noncontrolling Interest, Decrease from Distributions to Noncontrolling Interest Holders			(23,013)	(10,338)
Business Combination, Acquisition of Less than 100 Percent, Noncontrolling Interest, Fair Value		510,500		510,500
Noncontrolling Interest, Period Increase (Decrease), Foreign Exchange			1,810	(59)
Noncontrolling Interest [Member]
Noncontrolling Interest [Line Items]
Proceeds from (Payments to) Noncontrolling Interests	(2,693)		(2,693)	2,604
Redeemable Noncontrolling Interest, Equity, Carrying Amount	586,195	591,735	586,195	591,735	591,254		68,922
Net Income (Loss) Attributable to Redeemable Noncontrolling Interest			18,094	20,106
Noncontrolling Interest, Decrease from Distributions to Noncontrolling Interest Holders			(23,013)	10,338
Business Combination, Acquisition of Less than 100 Percent, Noncontrolling Interest, Fair Value		510,500		510,500
Noncontrolling Interest, Period Increase (Decrease), Foreign Exchange			1,810	(59)
Noncontrolling Interest, Change in Redemption Value			743
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]
Proceeds from (Payments to) Noncontrolling Interests	0			0
Redeemable Noncontrolling Interest, Equity, Carrying Amount	403,797	409,404	403,797	409,404	404,852		0
Net Income (Loss) Attributable to Redeemable Noncontrolling Interest			9,471	10,740
Noncontrolling Interest, Decrease from Distributions to Noncontrolling Interest Holders			(10,526)	4,536
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]
Proceeds from (Payments to) Noncontrolling Interests	0			0
Redeemable Noncontrolling Interest, Equity, Carrying Amount	110,889	108,205	110,889	108,205	113,173		0
Net Income (Loss) Attributable to Redeemable Noncontrolling Interest			6,434	5,638
Noncontrolling Interest, Decrease from Distributions to Noncontrolling Interest Holders			(9,461)	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]
Proceeds from (Payments to) Noncontrolling Interests	0			0
Redeemable Noncontrolling Interest, Equity, Carrying Amount	69,862	67,757	69,862	67,757	68,747		67,155
Net Income (Loss) Attributable to Redeemable Noncontrolling Interest			2,206	3,364
Noncontrolling Interest, Decrease from Distributions to Noncontrolling Interest Holders			(2,901)	2,703
Business Combination, Acquisition of Less than 100 Percent, Noncontrolling Interest, Fair Value		0		0
Noncontrolling Interest, Period Increase (Decrease), Foreign Exchange			1,810	(59)
Noncontrolling Interest, Change in Redemption Value			0
Other Affiliates [Member] | Noncontrolling Interest [Member]
Noncontrolling Interest [Line Items]
Proceeds from (Payments to) Noncontrolling Interests	(2,693)			2,604
Redeemable Noncontrolling Interest, Equity, Carrying Amount	$ 1,647	6,369	1,647	6,369	$ 4,482		$ 1,767
Net Income (Loss) Attributable to Redeemable Noncontrolling Interest			(17)	364
Noncontrolling Interest, Decrease from Distributions to Noncontrolling Interest Holders			(125)	366
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