Segment Reporting: (Details)	3 Months Ended		9 Months Ended
	Sep. 26, 2020 USD ($)	Sep. 28, 2019 USD ($)	Sep. 26, 2020 USD ($) item	Sep. 28, 2019 USD ($)	Dec. 28, 2019 USD ($)
Segment Reporting
Number of reportable business segments | item			2
Total revenue	$ 18,277,000	$ 19,680,900	$ 49,266,500	$ 55,416,300
Total operating income	12,497,800	12,274,700	29,277,400	32,188,100
Total depreciation and amortization	120,700	110,700	366,700	276,700
Total identifiable assets	35,838,600		35,838,600		$ 61,842,200
Operating | Franchising
Segment Reporting
Total revenue	15,581,200	15,305,400	37,225,700	42,682,500
Total operating income	10,789,900	9,895,700	22,601,000	25,844,500
Total depreciation and amortization	70,800	79,000	216,100	208,900
Total identifiable assets	4,285,500		4,285,500		3,736,000
Operating | Leasing
Segment Reporting
Total revenue	2,695,800	4,375,500	12,040,800	12,733,800
Total operating income	1,707,900	2,379,000	6,676,400	6,343,600
Total depreciation and amortization	49,900	$ 31,700	150,600	$ 67,800
Total identifiable assets	16,772,300		16,772,300		26,596,700
Unallocated
Segment Reporting
Total identifiable assets	$ 14,780,800		$ 14,780,800		$ 31,509,500