Pension and Other Postretirement - Components of Net Periodic Benefit Costs (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 28, 2015	Jun. 29, 2014	Jun. 28, 2015	Jun. 29, 2014
Pension Benefits [Member]
Components of net periodic benefit cost:
Service cost	$ 1,443	$ 1,816	$ 3,227	$ 3,580
Interest cost	2,207	2,722	4,747	5,403
Expected return on plan assets	(3,159)	(3,479)	(6,313)	(6,940)
Amortization of prior service credit	(15)		(26)
Actuarial losses	1,288	1,723	2,574	3,446
Net periodic benefit cost	1,764	2,782	4,209	5,489
Other Benefits [Member]
Components of net periodic benefit cost:
Service cost	16	30	32	60
Interest cost	399	525	802	1,077
Amortization of prior service credit	(25)	(27)	(50)	(53)
Actuarial losses	123	164	252	353
Net periodic benefit cost	$ 513	$ 692	$ 1,036	$ 1,437