Investments - Reconciliation of Other Investments (Details) - USD ($) $ in Thousands	12 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Reconciliation Of Other Investments [Roll Forward]
Other investments, beginning balance	$ 13,394
Other investments, ending balance	17,381	$ 13,394
Fair Value, Inputs, Level 3
Reconciliation Of Other Investments [Roll Forward]
Other investments, beginning balance	13,394	12,488
Contributions	246	4,401
Distributions	(3,540)	(2,747)
Net gain (loss) on other investments	7,469	(748)
Transfer out of Level 3	(4,271)
Other investments, ending balance	13,298	13,394
Private equity funds
Reconciliation Of Other Investments [Roll Forward]
Other investments, ending balance	6,254
Private equity funds | Fair Value, Inputs, Level 3
Reconciliation Of Other Investments [Roll Forward]
Other investments, beginning balance	5,786	3,734
Contributions	246	2,526
Distributions	(1,566)	(777)
Net gain (loss) on other investments	1,788	303
Transfer out of Level 3	0
Other investments, ending balance	6,254	5,786
Direct credit co-investments
Reconciliation Of Other Investments [Roll Forward]
Other investments, ending balance	985
Direct credit co-investments | Fair Value, Inputs, Level 3
Reconciliation Of Other Investments [Roll Forward]
Other investments, beginning balance	1,756	3,940
Contributions	0	0
Distributions	(1,025)	(1,970)
Net gain (loss) on other investments	254	(214)
Transfer out of Level 3	0
Other investments, ending balance	985	1,756
Direct equity co-investments
Reconciliation Of Other Investments [Roll Forward]
Other investments, ending balance	6,059
Direct equity co-investments | Fair Value, Inputs, Level 3
Reconciliation Of Other Investments [Roll Forward]
Other investments, beginning balance	5,852	4,814
Contributions	0	1,875
Distributions	(949)	0
Net gain (loss) on other investments	5,427	(837)
Transfer out of Level 3	(4,271)
Other investments, ending balance	$ 6,059	$ 5,852