Investments in Securities and Derivative Instruments - Textual (Details) - USD ($)	3 Months Ended						9 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Dec. 31, 2020	Dec. 31, 2019	Mar. 31, 2020
Derivatives, Fair Value
Unrealized gain (loss) on interest rate swaps, net of tax	$ 71,000	$ 55,000	$ (26,000)	$ 94,000	$ (88,000)	$ (176,000)	$ 100,000	$ (170,000)
Gain from equity investments	800,000						1,600,000
Loss from equity investments	300,000						1,100,000
Margin accounts outstanding	700,000			400,000			700,000	400,000
Cash margin balances related to exchange-traded equity securities	$ 1,300,000			$ 300,000			$ 1,300,000	$ 300,000
Interest rate on margin account borrowings (percent)	9.50%						9.50%
Level 1
Derivatives, Fair Value
Gross gain from derivative instrument	$ 800,000						$ 100,000
Gross loss from derivative instrument	23,700						1,600
Interest Rate Swap
Derivatives, Fair Value
Unrealized gain (loss) on interest rate swaps, net of tax	71,000.0						100,000
Interest Rate Swap | Level 2 | Other non-current liabilities
Derivatives, Fair Value
Derivative liability	$ 800,000						$ 800,000		$ 900,000
Unsecured Debt | Interest Rate Swap | Term Note A - MBT
Derivatives, Fair Value
Interest rate	4.56%						4.56%
Unsecured Debt | Interest Rate Swap | Term Note D - MBT
Derivatives, Fair Value
Interest rate	5.09%						5.09%