Retirement Plans - Components of Net Periodic Pension and Other Postretirement Benefit Costs (Credits) (Detail) - USD ($)		12 Months Ended
	Sep. 30, 2015	Dec. 30, 2017	Dec. 31, 2016	Jan. 02, 2016
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Curtailment	$ 0
Pension Benefits [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Service cost		$ 2,356,000	$ 3,849,000	$ 32,582,000
Interest cost		39,474,000	40,459,000	39,628,000
Expected return on plan assets		(47,828,000)	(48,296,000)	(54,881,000)
Amortization of prior service cost (credit)		138,000	157,000	195,000
Amortization of net (gain) loss		3,848,000	8,255,000	10,394,000
Settlements		17,785,000	4,487,000	3,358,000
Curtailment		138,000
Special termination benefit				422,000
Net periodic benefit costs		15,911,000	8,911,000	31,698,000
Other Postretirement Plans [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Service cost		35,000	37,000	37,000
Interest cost		283,000	296,000	264,000
Amortization of prior service cost (credit)		6,000	6,000	(62,000)
Amortization of net (gain) loss		(148,000)	(71,000)	14,000
Net periodic benefit costs		$ 176,000	$ 268,000	$ 253,000