Pensions and Other Post-employment Benefits (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 26, 2020	Jun. 28, 2019	Jun. 26, 2020	Jun. 28, 2019
Components of net periodic benefit cost
Net pension settlements/curtailments		$ (3,296)	$ (94)	$ (3,296)
Pension Benefits
Components of net periodic benefit cost
Service cost	$ 0	1,418	0	2,758
Interest cost	1,215	1,347	2,429	2,904
Expected return on plan assets	(2,205)	(2,167)	(4,410)	(4,290)
Amortization of prior service cost (benefit)	0	122	0	242
Amortization of net loss (gain)	284	627	568	1,431
Net periodic benefit (credit) cost	(706)	1,347	(1,413)	3,045
Net pension settlements/curtailments	94	3,296	94	3,296
Total net benefit cost	(612)	4,643	(1,319)	6,341
Other Benefits
Components of net periodic benefit cost
Service cost	15	18	31	35
Interest cost	53	99	107	199
Expected return on plan assets	0	0	0	0
Amortization of prior service cost (benefit)	(374)	(375)	(749)	(749)
Amortization of net loss (gain)	(83)	(23)	(166)	(46)
Net periodic benefit (credit) cost	(389)	(281)	(777)	(561)
Net pension settlements/curtailments	0	0	0	0
Total net benefit cost	$ (389)	$ (281)	$ (777)	$ (561)