Postretirement Benefits Components of Net Periodic Postretirement Benefit Income (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 29, 2019	Dec. 30, 2018	Dec. 31, 2017
Retirement Benefits [Abstract]
Service cost	$ 145	$ 196	$ 192
Interest cost	150	178	191
Amortization of net loss	(66)	(208)	(222)
Amortization of prior service credit	(350)	(352)	(355)
Net periodic postretirement benefit income	$ 11	$ 230	$ 250