Fair Values of Assets and Liabilities by Level (Details 1) - USD ($) $ in Thousands	Jun. 30, 2020	Mar. 31, 2020
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity Method Investments	$ 28,694	$ 28,373
Consolidated Entity Excluding Variable Interest Entities (VIE) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Business Combination, Contingent Consideration, Liability	0	0
Derivative Liability, Fair Value, Amount Not Offset Against Collateral	0	0
Consolidated Entity Excluding Variable Interest Entities (VIE) [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and Cash Equivalents, Fair Value Disclosure	326,224	594,514
Derivative Asset, Fair Value, Amount Not Offset Against Collateral	4,173	4,716
Assets, Fair Value Disclosure	663,224	871,467
Business Combination, Contingent Consideration, Liability	0	0
Derivative Liability, Fair Value, Amount Not Offset Against Collateral	(1,557)	(13,872)
Financial Liabilities Fair Value Disclosure	(1,557)	(13,872)
Consolidated Entity Excluding Variable Interest Entities (VIE) [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and Cash Equivalents, Fair Value Disclosure	259,387	12,521
Assets, Fair Value Disclosure	296,116	33,636
Business Combination, Contingent Consideration, Liability	0	0
Derivative Liability, Fair Value, Amount Not Offset Against Collateral	0	0
Financial Liabilities Fair Value Disclosure	0	0
Consolidated Entity Excluding Variable Interest Entities (VIE) [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure	83,483	82,002
Business Combination, Contingent Consideration, Liability	(3,380)	(3,308)
Derivative Liability, Fair Value, Amount Not Offset Against Collateral	0	0
Financial Liabilities Fair Value Disclosure	(3,380)	(3,308)
Consolidated Entity Excluding Variable Interest Entities (VIE) [Member] | Fair Value Measured at Net Asset Value Per Share [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure	30,656	27,589
Financial Liabilities Fair Value Disclosure	0	0
Consolidated Entity Excluding Variable Interest Entities (VIE) [Member] | Fair Value, Inputs, Level 1, 2 and 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and Cash Equivalents, Fair Value Disclosure	585,611	607,035
Derivative Asset, Fair Value, Amount Not Offset Against Collateral	4,173	4,716
Assets, Fair Value Disclosure	1,073,479	1,014,694
Business Combination, Contingent Consideration, Liability	(3,380)	(3,308)
Derivative Liability, Fair Value, Amount Not Offset Against Collateral	(1,557)	(13,872)
Financial Liabilities Fair Value Disclosure	(4,937)	(17,180)
Consolidated Entity Excluding Variable Interest Entities (VIE) [Member] | Proprietary Funds [Member] | Current Investments [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity Securities, FV-NI	64,863	48,940
Consolidated Entity Excluding Variable Interest Entities (VIE) [Member] | Proprietary Funds [Member] | Current Investments [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity Securities, FV-NI	27,711	19,538
Consolidated Entity Excluding Variable Interest Entities (VIE) [Member] | Proprietary Funds [Member] | Current Investments [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity Securities, FV-NI	41,626	38,895
Consolidated Entity Excluding Variable Interest Entities (VIE) [Member] | Proprietary Funds [Member] | Current Investments [Member] | Fair Value Measured at Net Asset Value Per Share [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity Securities, FV-NI	1,072	1,360
Consolidated Entity Excluding Variable Interest Entities (VIE) [Member] | Proprietary Funds [Member] | Current Investments [Member] | Fair Value, Inputs, Level 1, 2 and 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity Securities, FV-NI	135,272	108,733
Consolidated Entity Excluding Variable Interest Entities (VIE) [Member] | Proprietary Funds [Member] | Other Noncurrent Assets [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity Method Investments, Fair Value Disclosure	5,000
Consolidated Entity Excluding Variable Interest Entities (VIE) [Member] | Proprietary Funds [Member] | Other Noncurrent Assets [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity Method Investments, Fair Value Disclosure	41,716	43,059
Consolidated Entity Excluding Variable Interest Entities (VIE) [Member] | Proprietary Funds [Member] | Other Noncurrent Assets [Member] | Fair Value Measured at Net Asset Value Per Share [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity Method Investments, Fair Value Disclosure	12,695	12,571
Consolidated Entity Excluding Variable Interest Entities (VIE) [Member] | Proprietary Funds [Member] | Other Noncurrent Assets [Member] | Fair Value, Inputs, Level 1, 2 and 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity Method Investments, Fair Value Disclosure	59,411	55,630
Consolidated Entity Excluding Variable Interest Entities (VIE) [Member] | Long Term Incentive Compensation Plans [Member] | Current Investments [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity Securities, FV-NI	260,028	210,891
Consolidated Entity Excluding Variable Interest Entities (VIE) [Member] | Long Term Incentive Compensation Plans [Member] | Current Investments [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity Securities, FV-NI	0	0
Consolidated Entity Excluding Variable Interest Entities (VIE) [Member] | Long Term Incentive Compensation Plans [Member] | Current Investments [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity Securities, FV-NI	0	0
Consolidated Entity Excluding Variable Interest Entities (VIE) [Member] | Long Term Incentive Compensation Plans [Member] | Current Investments [Member] | Fair Value Measured at Net Asset Value Per Share [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity Securities, FV-NI	0
Equity Method Investments, Fair Value Disclosure	8,556	5,287
Consolidated Entity Excluding Variable Interest Entities (VIE) [Member] | Long Term Incentive Compensation Plans [Member] | Current Investments [Member] | Fair Value, Inputs, Level 1, 2 and 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity Securities, FV-NI	260,028	210,891
Equity Method Investments, Fair Value Disclosure	11,056	5,287
Consolidated Entity Excluding Variable Interest Entities (VIE) [Member] | Long Term Incentive Compensation Plans [Member] | Other Noncurrent Assets [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity Method Investments, Fair Value Disclosure	2,500
Consolidated Entity Excluding Variable Interest Entities (VIE) [Member] | Other Investments [Member] | Current Investments [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity Securities, FV-NI	7,936	12,406
Consolidated Entity Excluding Variable Interest Entities (VIE) [Member] | Other Investments [Member] | Current Investments [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity Securities, FV-NI	1,518	1,577
Consolidated Entity Excluding Variable Interest Entities (VIE) [Member] | Other Investments [Member] | Current Investments [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity Securities, FV-NI	0	0
Consolidated Entity Excluding Variable Interest Entities (VIE) [Member] | Other Investments [Member] | Current Investments [Member] | Fair Value Measured at Net Asset Value Per Share [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity Securities, FV-NI	0	0
Consolidated Entity Excluding Variable Interest Entities (VIE) [Member] | Other Investments [Member] | Current Investments [Member] | Fair Value, Inputs, Level 1, 2 and 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity Securities, FV-NI	9,454	13,983
Consolidated Entity Excluding Variable Interest Entities (VIE) [Member] | Other Investments [Member] | Other Noncurrent Assets [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity Method Investments, Fair Value Disclosure	141	48
Consolidated Entity Excluding Variable Interest Entities (VIE) [Member] | Other Investments [Member] | Other Noncurrent Assets [Member] | Fair Value Measured at Net Asset Value Per Share [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity Method Investments, Fair Value Disclosure	8,333	8,371
Consolidated Entity Excluding Variable Interest Entities (VIE) [Member] | Other Investments [Member] | Other Noncurrent Assets [Member] | Fair Value, Inputs, Level 1, 2 and 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity Method Investments, Fair Value Disclosure	$ 8,474	$ 8,419