Investments - Valuation Methodologies (Details) $ in Thousands	Mar. 31, 2021 USD ($)	Mar. 31, 2020 USD ($)
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Other investments	$ 17,381	$ 13,394
Private equity funds
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Other investments	6,254
Direct credit co-investments
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Other investments	985
Direct equity co-investments
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Other investments	$ 6,059
Selected market return | Adjusted net asset value | Minimum | Private equity funds
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Range of and weighted-average inputs	0.02	(0.074)
Selected market return | Adjusted net asset value | Maximum | Private equity funds
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Range of and weighted-average inputs	0.124	(0.03)
Selected market return | Adjusted net asset value | Weighted Average | Private equity funds
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Range of and weighted-average inputs	0.042	(0.062)
Market yield | Discounted cash flow | Minimum | Direct credit co-investments
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Range of and weighted-average inputs	0.093	0.115
Market yield | Discounted cash flow | Maximum | Direct credit co-investments
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Range of and weighted-average inputs	0.093	0.126
Market yield | Discounted cash flow | Weighted Average | Direct credit co-investments
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Range of and weighted-average inputs	0.093	0.125
EBITDA multiple | Market approach | Minimum | Direct equity co-investments
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Range of and weighted-average inputs	7.75	7.25
EBITDA multiple | Market approach | Maximum | Direct equity co-investments
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Range of and weighted-average inputs	14.75	12
EBITDA multiple | Market approach | Weighted Average | Direct equity co-investments
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Range of and weighted-average inputs	10.42	9.93
Equity multiple | Market approach | Direct equity co-investments
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Range of and weighted-average inputs	1.52	1.05
Equity multiple | Market approach | Weighted Average | Direct equity co-investments
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Range of and weighted-average inputs	1.52	1.05