Postretirement Benefits Change in Accumulated Other Comprehensive Income (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Jan. 01, 2017	Jan. 03, 2016
Compensation and Retirement Disclosure [Abstract]
Net actuarial (gain) loss	$ (122)	$ 1,251
Amortization of net loss	(222)	(197)
Amortization of prior service credit	355	355
Deferred income taxes	4	541
Total recognized in accumulated other comprehensive income	$ 7	$ 868	$ (22)