Debt: Notes Payable (Details) - Prudential Investment Management, Inc - USD ($)	1 Months Ended	9 Months Ended
	Sep. 30, 2021	Sep. 25, 2021	Aug. 31, 2017	May 31, 2015
Notes Payable.
Notes Payable
Amount of additional senior secured notes available for issuance	$ 30,000,000.0
Principal amount outstanding		$ 48,750,000
Minimum prepayment		1,000,000.0
Series A Notes
Notes Payable
Principal amount outstanding		$ 11,250,000
Note payable, face amount				$ 25,000,000.0
Term of notes payable		10 years
Interest rate (as a percent)		5.50%
Quarterly principal payment, first five years		$ 500,000
Quarterly principal payment, thereafter		750,000
Series B Notes
Notes Payable
Principal amount outstanding		$ 7,500,000
Note payable, face amount			$ 12,500,000
Term of notes payable		10 years
Interest rate (as a percent)		5.10%
Quarterly principal payment		$ 312,500
Series C Notes
Notes Payable
Note payable, face amount	$ 30,000,000.0
Term of notes payable	7 years
Interest rate (as a percent)	3.18%