Postretirement Benefits Other Than Pensions - Additional Information (Detail) (Other Postretirement Benefit Plans, Defined Benefit, USD $)	12 Months Ended
	Dec. 28, 2014	Dec. 29, 2013
Other Postretirement Benefit Plans, Defined Benefit
Defined Benefit Plan Disclosure [Line Items]
Net actuarial losses	$ (12,594,000)	$ (6,087,000)
Prior service credits	42,542,000	16,204,000
Amounts in accumulated other comprehensive income (loss)	29,948,000	10,117,000
Actuarial loss estimated to be amortized from accumulated other comprehensive loss into net periodic benefit cost	1,500,000
Prior service credit estimated to be amortized from accumulated other comprehensive loss into net periodic benefit cost	10,000,000
Percentage of change in the health care cost trend rate	1.00%
Effect on postretirement benefit obligation of a 1% change in the health care cost trend rate	$ 300,000