Summary of Significant Accounting Policies - Property, Plant and Equipment and Lease Fleet (Details) - USD ($)	3 Months Ended	12 Months Ended
	Sep. 30, 2020	Jun. 30, 2020
Property, Plant and Equipment
Property, plant and equipment, gross	$ 73,499,000	$ 72,147,000
Less accumulated depreciation and amortization	(49,435,000)	(47,751,000)
Property, plant and equipment, net	24,064,000	24,396,000
Depreciation expense, PP&E	1,637,000	1,586,000
Land
Property, Plant and Equipment
Property, plant and equipment, gross	2,168,000	2,168,000
Building and improvements
Property, Plant and Equipment
Property, plant and equipment, gross	$ 4,899,000	4,899,000
Building and improvements | Minimum
Property, Plant and Equipment
Estimated Useful Life	10 years
Building and improvements | Maximum
Property, Plant and Equipment
Estimated Useful Life	40 years
Transportation and plant equipment (including finance lease assets)
Property, Plant and Equipment
Property, plant and equipment, gross	$ 51,522,000	50,497,000
Transportation and plant equipment (including finance lease assets) | Minimum
Property, Plant and Equipment
Estimated Useful Life	3 years
Transportation and plant equipment (including finance lease assets) | Maximum
Property, Plant and Equipment
Estimated Useful Life	20 years
Furniture, fixtures and office equipment
Property, Plant and Equipment
Property, plant and equipment, gross	$ 14,910,000	14,583,000
Furniture, fixtures and office equipment | Minimum
Property, Plant and Equipment
Estimated Useful Life	3 years
Furniture, fixtures and office equipment | Maximum
Property, Plant and Equipment
Estimated Useful Life	10 years
Lease Fleet
Lease Fleet
Gross costs of leased fleet	$ 618,643,000	613,358,000
Depreciation expense, leased fleet	$ 6,755,000	$ 6,959,000