Benefit Plans - Net Periodic Postretirement Benefit Cost (Detail) - Postretirement Benefits [Member] - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 27, 2015	Sep. 28, 2014	Sep. 27, 2015	Sep. 28, 2014
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 325	$ 382	$ 975	$ 1,148
Interest cost	708	825	2,123	2,475
Recognized net actuarial loss	717	562	2,152	1,688
Amortization of prior service cost	(840)	(377)	(2,520)	(1,133)
Net periodic pension cost (benefit)	$ 910	$ 1,392	$ 2,730	$ 4,178