Investments in Securities and Derivative Instruments - Narrative (Details) - USD ($)		2 Months Ended	3 Months Ended				6 Months Ended
	Mar. 30, 2023	Feb. 24, 2022	Sep. 30, 2023	Jun. 30, 2023	Sep. 30, 2022	Jun. 30, 2022	Sep. 30, 2023	Sep. 30, 2022	Mar. 31, 2023	Jan. 07, 2022	Aug. 31, 2021
Derivatives, Fair Value
Long-term debt, gross			$ 108,819,000				$ 108,819,000		$ 125,914,000
Derivative loss		$ 100,000
Repayments of Long-term Debt							15,438,000	$ 4,112,000
Unrealized gain on interest rate swaps, net of tax			16,000	$ 24,000	$ 957,000	$ 475,000
Gross unrealized gain from equity investments			400,000		43,000		900,000	100,000
Gross unrealized loss from equity investments			1,100,000		200,000		1,800,000	300,000
Unsecured Debt | Contrail Debt
Derivatives, Fair Value
Interest rate stated percentage (as a percentage)										4.68%
Long-term debt, gross			28,139,000				28,139,000		50,621,000	$ 43,600,000
Unsecured Debt | Parent Company
Derivatives, Fair Value
Long-term debt, gross			54,149,000				54,149,000		47,963,000
Interest Rate Swap
Derivatives, Fair Value
Unrealized gain on interest rate swaps, net of tax			16,000		$ 1,000,000		40,000	$ 1,400,000
Interest Rate Swap | Level 2
Derivatives, Fair Value
Derivative asset			$ 2,700,000				$ 2,700,000		2,400,000
Term Note A - MBT | Unsecured Debt | Parent Company
Derivatives, Fair Value
Interest rate stated percentage (as a percentage)			3.42%				3.42%				3.42%
Long-term debt, gross			$ 7,363,000				$ 7,363,000		7,762,000
Term Note A - MBT | Interest Rate Swap | Unsecured Debt
Derivatives, Fair Value
Interest rate stated percentage (as a percentage)			4.56%				4.56%
Term Note D - MBT | Unsecured Debt | Parent Company
Derivatives, Fair Value
Interest rate stated percentage (as a percentage)			5.09%				5.09%
Long-term debt, gross			$ 1,304,000				$ 1,304,000		$ 1,338,000
Term Note G | Unsecured Debt | Contrail Debt
Derivatives, Fair Value
Repayments of Long-term Debt	$ 6,700,000