Investment in Leasing Operations: Credit Losses (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 26, 2020	Sep. 28, 2019	Sep. 26, 2020	Sep. 28, 2019	Dec. 28, 2019
Activity in the allowance for credit losses for leasing operations
Balance at beginning of period			$ 580,600	$ 861,200
Provision for credit losses	$ (339,600)	$ (55,500)	164,300	23,900
Recoveries			(12,400)	15,700
Deductions for amounts written-off			(148,900)	(224,000)
Balance at end of period	583,600	$ 676,800	583,600	$ 676,800
Investment In Leases
Total investment in direct financing and sales-type leases	16,045,700		16,045,700		$ 25,657,400
Allowance for Credit Losses
Total	583,600		583,600		580,600
Investment in leases
Investment In Leases
Collectively evaluated for loss potential	16,045,700		16,045,700		25,657,400
Total investment in direct financing and sales-type leases	16,045,700		16,045,700		25,657,400
Allowance for Credit Losses
Collectively evaluated for loss potential	583,600		583,600		580,600
Total	$ 583,600		$ 583,600		$ 580,600