Employee Retirement and Pension Benefits - Components of Pension Benefit/ Expense (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 27, 2020	Jun. 29, 2019	Jun. 27, 2020	Jun. 29, 2019
Retirement Benefits [Abstract]
Administrative cost	$ 300	$ 1,250	$ 1,550	$ 2,500
Interest cost	2,375	3,725	6,100	7,450
Expected return on plan assets	(6,300)	(4,650)	(10,950)	(9,300)
Amortization of net actuarial pension loss	1,225	2,225	3,450	4,450
Pension benefit expense	$ (2,400)	$ 2,550	$ 150	$ 5,100