Operating Leases: Summary (Details)	12 Months Ended
	Dec. 25, 2021 USD ($) item	Dec. 26, 2020 USD ($)	Dec. 28, 2019 USD ($)
Operating Leases
Remaining lease term	8 years
Discount rate (as a percent)	5.50%
Rent expense | $	$ 1,178,400	$ 1,195,000	$ 1,358,000
Corporate headquarters, Minnesota
Operating Leases
Lease renewal option	true
Number of lease extension periods | item	2
Lease renewal term	5 years