Debt: Notes Payable (Details) - Prudential Investment Management, Inc - USD ($)	6 Months Ended
	Jun. 30, 2018	Aug. 31, 2017	May 31, 2015
Notes Payable
Notes Payable
Minimum prepayment	$ 1,000,000
Series A Notes
Notes Payable
Principal amount outstanding	$ 19,000,000
Note payable, face amount			$ 25,000,000
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	$ 11,600,000
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