Debt: Line of Credit (Details) - Private Bank, Trust Company and BMO Harris Bank N A $ in Millions	1 Months Ended		12 Months Ended
	May 02, 2015 USD ($)	Mar. 28, 2015 USD ($)	Dec. 31, 2016 USD ($) item	May 28, 2016 USD ($)
One month LIBOR
Line of Credit
Variable rate basis			one month LIBOR
Two month LIBOR
Line of Credit
Variable rate basis			two month LIBOR
Three month LIBOR
Line of Credit
Variable rate basis			three month LIBOR
Six month LIBOR
Line of Credit
Variable rate basis			six month LIBOR
Twelve month LIBOR
Line of Credit
Variable rate basis			twelve month LIBOR
Line of Credit
Line of Credit
Borrowings outstanding			$ 23.4
Proposed Maximum Line Of Credit	$ 60.0	$ 35.0
Leverage Ratio Amendment Term	2 years
Amount Of Term Note Available Borrowing Upon Tender Offer Effective Date	$ 30.0
Automatic deduction in the aggregate commitments under the line of credit effective May 2016 and each subsequent May thereafter through the term of the facility				$ 5.0
Borrowing availability			$ 31.6
Number of interest rate options | item			2
Non-utilization fees (as a percent)			0.25%
Line of Credit | Minimum
Line of Credit
Interest rate (as a percent)			2.95%
Line of Credit | Maximum
Line of Credit
Interest rate (as a percent)			3.75%
Line of Credit | Base Rate
Line of Credit
Variable rate basis			Base Rate
Applicable margin (as a percent)			0.00%
Line of Credit | LIBOR
Line of Credit
Variable rate basis			LIBOR
Applicable margin (as a percent)			2.25%