Retirement Plans - Net Pension Income Domestic and Foreign (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 28, 2015	Jun. 30, 2016	Jun. 28, 2015
Pension Plans
Net pension expense (income)
(Income) expense, net	$ (402)	$ (530)	$ (794)	$ (1,059)
United States Pension Plan of US Entity [Member]
Net pension expense (income)
Service cost	22	42	44	86
Interest cost	2,756	2,815	5,512	5,629
Expected return on plan assets	(4,744)	(5,068)	(9,488)	(10,136)
Amortization of loss	1,498	1,585	2,996	3,169
Other cost due to retirement			12	0
(Income) expense, net	(468)	(626)	(924)	(1,252)
Foreign Pension Plans
Net pension expense (income)
Service cost	13	16	25	33
Interest cost	11	124	22	247
Expected return on plan assets	7	(134)	14	(267)
Amortization of loss	35	90	69	180
Other cost due to retirement			0	0
(Income) expense, net	$ 66	$ 96	$ 130	$ 193