Debt: Line of Credit (Details) $ in Millions	12 Months Ended
	Dec. 28, 2019 USD ($) item	Jul. 31, 2017 USD ($)
Private Bank, Trust Company and BMO Harris Bank N A | One month LIBOR
Line of Credit
Variable rate basis	one month LIBOR
Private Bank, Trust Company and BMO Harris Bank N A | Two month LIBOR
Line of Credit
Variable rate basis	two month LIBOR
Private Bank, Trust Company and BMO Harris Bank N A | Three month LIBOR
Line of Credit
Variable rate basis	three month LIBOR
Private Bank, Trust Company and BMO Harris Bank N A | Six month LIBOR
Line of Credit
Variable rate basis	six month LIBOR
Private Bank, Trust Company and BMO Harris Bank N A | Twelve month LIBOR
Line of Credit
Variable rate basis	twelve month LIBOR
Line of Credit
Line of Credit
Borrowings outstanding	$ 0.0
Line of Credit | Private Bank, Trust Company and BMO Harris Bank N A
Line of Credit
Terms notes, available borrowing to fund Tender Offer		$ 15.0
Automatic deduction in the aggregate commitments under the line of credit effective July 2019 and each subsequent July thereafter through the term of the facility		$ 5.0
Line of credit available for additional borrowings	$ 45.0
Number of interest rate options | item	2
Non-utilization fees (as a percent)	0.25%
Line of Credit | Private Bank, Trust Company and BMO Harris Bank N A | Base Rate
Line of Credit
Variable rate basis	Base Rate
Applicable margin (as a percent)	0.00%
Line of Credit | Private Bank, Trust Company and BMO Harris Bank N A | LIBOR
Line of Credit
Variable rate basis	LIBOR
Applicable margin (as a percent)	2.00%