Income Taxes: Other (Details) - USD ($)	12 Months Ended
	Dec. 29, 2018	Dec. 30, 2017	Dec. 31, 2016	Dec. 26, 2015
Tax Act
Corporate income tax rate (as a percent)		35.00%	35.00%	35.00%
Reduction of income tax expense related to the decrease in the federal income tax rate		$ 1,500,000
Excess tax benefits related to stock option exercises
Excess tax benefits related to stock option exercises, credited to stockholders' equity		0	$ 599,400	$ 26,300
Unrecognized Tax Benefits
Unrecognized tax benefits, including interest and penalties		583,100	502,000
Interest and penalties accrued related to unrecognized tax benefit		32,000	22,500
Activity related to the company's unrecognized tax benefits
Balance at the beginning of the period	$ 551,100	479,500	469,900
Increases related to current year tax positions		192,900	128,500
Subtractions for tax positions of prior years		(8,300)	(5,300)
Expiration of the statute of limitations for the assessment of taxes		(113,000)	(113,600)
Balance at the end of the period		$ 551,100	$ 479,500	$ 469,900
Period over which various statutes of limitations are expected to expire		12 months
Scenario, Forecast
Tax Act
Corporate income tax rate (as a percent)	21.00%