Shareholders' Equity (Deficit): Stock Option Plans and Stock-Based Compensation (Details) - USD ($)	9 Months Ended		12 Months Ended
	Sep. 26, 2020	Sep. 28, 2019	Dec. 28, 2019	Apr. 29, 2020
2020 Plan
Stock Option Plans
Number of shares authorized for issuance				100,000
2010 Plan
Stock Option Plans
Number of shares authorized and unissued under the plan				125,465
Nonemployee Directors Plan
Stock Option Plans
Number of shares authorized and unissued under the plan				24,500
Stock options
Number of Shares
Outstanding at the beginning of the period (in shares)	479,558
Granted (in shares)	22,550
Exercised (in shares)	(87,579)
Forfeited (in shares)	(23,000)
Outstanding at the end of the period (in shares)	391,529		479,558
Exercisable at the end of the period (in shares)	279,164
Weighted Average Exercise Price
Outstanding at the beginning of the period (in dollars per share)	$ 101.78
Granted (in dollars per share)	143.87
Exercised (in dollars per share)	80.77
Forfeited (in dollars per share)	148.16
Outstanding at the end of the period (in dollars per share)	106.18		$ 101.78
Exercisable at the end of the period (in dollars per share)	$ 87.77
Weighted Average Remaining Contractual Life (years)
Outstanding	5 years 4 months 28 days		5 years 9 months 14 days
Exercisable at the end of the period	4 years 2 months 19 days
Intrinsic Value
Outstanding	$ 23,296,200		$ 45,283,200
Exercisable at the end of the period	$ 21,578,700
Weighted average assumptions and results used in estimation of fair value of options granted
Risk free interest rate (as a percent)	0.40%	1.98%
Expected life (years)	6 years	6 years
Expected volatility (as a percent)	25.03%	20.30%
Dividend yield (as a percent)	1.92%	1.26%
Option fair value (in dollars per share)	$ 26.55	$ 32.65
Additional disclosures
Compensation expense	$ 929,900	$ 1,511,400
Total unrecognized compensation expense	$ 2,700,000
Weighted average period for recognition of unrecognized compensation expense	2 years 4 months 24 days