Pension and Postretirement Benefits (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jul. 01, 2018	Jul. 02, 2017	Jul. 01, 2018	Jul. 02, 2017	Dec. 31, 2017
Defined Benefit Plan Plan Amendment [Abstract]
Defined Benefit Plan Accumulated Benefit Obligation Increase For Plan Amendment	$ 35,192
Date of resolution approval plan termination	February 2018
Pension [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	$ 667	$ 921	$ 1,352	$ 1,873
Interest cost	3,980	4,430	7,996	9,155
Expected return on assets	(5,174)	(5,880)	(10,379)	(12,161)
Net amortization and deferrals	2,965	2,519	5,942	5,213
Net periodic benefit cost	$ 2,438	1,990	4,911	4,080
Contributions to defined benefit pension plans			540
Expected fiscal year defined benefit pension plan contributions			$ 1,300
Weighted average discount rate	3.20%		3.20%		3.70%
Postretirement [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	$ 189	173	$ 377	345
Interest cost	293	295	585	590
Expected return on assets	0	0	0	0
Net amortization and deferrals	43	0	85	0
Net periodic benefit cost	$ 525	$ 468	$ 1,047	$ 935