Debt: Notes Payable (Details) - USD ($)	1 Months Ended	9 Months Ended
	Apr. 30, 2022	Sep. 30, 2023	Sep. 30, 2021	Aug. 31, 2017	May 31, 2015
Note Agreement | Notes Payable.
Notes Payable
Principal amount outstanding		$ 40,300,000
Minimum prepayment		1,000,000.0
Note Agreement | Series A Notes
Notes Payable
Principal amount outstanding		$ 5,300,000
Note payable, face amount					$ 25,000,000.0
Debt term		10 years
Interest rate (as a percent)		5.50%
Quarterly principal payment, first five years		$ 500,000
Quarterly principal payment, thereafter		750,000
Note Agreement | Series B Notes
Notes Payable
Principal amount outstanding		$ 5,000,000.0
Note payable, face amount				$ 12,500,000
Debt term		10 years
Interest rate (as a percent)		5.10%
Quarterly principal payment		$ 312,500
Note Agreement | Series C Notes
Notes Payable
Principal amount outstanding		$ 30,000,000.0
Note payable, face amount			$ 30,000,000.0
Debt term		7 years
Interest rate (as a percent)		3.18%
Shelf Agreement | Senior Notes
Notes Payable
Shelf Agreement term	3 years
Maximum amount of Shelf Notes available for issuance.	$ 100,000,000.0
Minimum prepayment	$ 1,000,000
Shelf Agreement | Senior Notes | Maximum
Notes Payable
Debt term	12 years 6 months