Investment in Leasing Operations: Credit Losses (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jul. 01, 2017	Jun. 25, 2016	Jul. 01, 2017	Jun. 25, 2016	Dec. 31, 2016
Activity in the allowance for credit losses for leasing operations
Balance at beginning of period			$ 896,000	$ 859,100
Provision for credit losses	$ (11,500)	$ (7,900)	(12,900)	(22,300)
Provisions charged to expense			(12,900)	(22,300)
Recoveries			10,200	9,600
Deductions for amounts written-off				(29,300)
Balance at end of period	893,300	$ 817,100	893,300	$ 817,100
Investment In Leases
Collectively evaluated for loss potential	41,403,000		41,403,000		$ 42,286,700
Total investment in direct financing and sales-type leases	41,403,000		41,403,000		42,286,700
Allowance for Credit Losses
Collectively evaluated for loss potential	893,300		893,300		896,000
Total	$ 893,300		$ 893,300		$ 896,000