FAIR VALUE MEASUREMENTS: Recurring Basis (Details) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014	Jun. 28, 2014
Fair value on a recurring basis
Industrial revenue development bonds, carrying amount, approximates fair value	$ 7,500	$ 7,500	$ 7,500
Cost Basis | Level 2
Fair value on a recurring basis
Industrial revenue development bonds, carrying amount, approximates fair value	7,500	7,500	7,500
Estimated Fair Value | Level 2
Fair value on a recurring basis
Industrial revenue development bonds, carrying amount, approximates fair value	$ 7,500	$ 7,500	$ 7,500