Pension and Other Postretirement Benefits - Other Postretirement Benefits (Details) - Other Postretirement Benefit Plan - USD ($) $ in Thousands	3 Months Ended
	Mar. 29, 2020	Mar. 31, 2019
Pension Benefits
Service cost	$ 7	$ 7
Interest cost	256	400
Amortization of actuarial loss	763	844
Amortization of prior service credit	(1,056)	(1,191)
Net periodic postretirement benefit income	$ (30)	$ 60