Investments in Securities and Derivative Instruments - Narrative (Details) - USD ($)		2 Months Ended	3 Months Ended						9 Months Ended
	Mar. 30, 2023	Feb. 24, 2022	Dec. 31, 2023	Sep. 30, 2023	Jun. 30, 2023	Dec. 31, 2022	Sep. 30, 2022	Jun. 30, 2022	Dec. 31, 2023	Dec. 31, 2022	Mar. 31, 2023	Jan. 07, 2022	Aug. 31, 2021
Derivatives, Fair Value
Long-term debt, gross			$ 101,231,000						$ 101,231,000		$ 125,914,000
Derivative loss		$ 100,000
Repayments of Long-term Debt									17,116,000	$ 12,300,000
Unrealized gain (loss) on interest rate swaps, net of tax			(38,000)	$ 16,000	$ 24,000	$ (61,000)	$ 957,000	$ 475,000
Gross unrealized gain from equity investments			500,000			300,000			1,400,000	300,000
Gross unrealized loss from equity investments			0			500,000			1,800,000	800,000
Unsecured debt | Contrail Debt
Derivatives, Fair Value
Interest rate stated percentage (as a percentage)												4.68%
Long-term debt, gross			24,918,000						24,918,000		50,621,000	$ 43,600,000
Unsecured debt | Parent company
Derivatives, Fair Value
Long-term debt, gross			50,962,000						50,962,000		47,963,000
Interest rate swap
Derivatives, Fair Value
Unrealized gain (loss) on interest rate swaps, net of tax			(38,000)			$ (100,000)			2,000	$ 1,400,000
Interest rate swap | Level 2
Derivatives, Fair Value
Derivative asset			$ 1,800,000						$ 1,800,000		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			$ 7,160,000						$ 7,160,000		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			$ 1,287,000						$ 1,287,000		$ 1,338,000
Term Note G | Unsecured debt | Contrail Debt
Derivatives, Fair Value
Repayments of Long-term Debt	$ 6,700,000