Benefit Plans - Significant Assumptions Used (Detail)	12 Months Ended
	Dec. 31, 2017	Jan. 01, 2017	Jan. 03, 2016
Net periodic pension cost for the fiscal year:
Weighted average expected long-term rate of return on plan assets	6.00%
Primary Plan [Member]
Projected benefit obligation at the measurement date:
Discount rate	3.80%	4.44%	4.72%
Bargaining Plan [Member]
Projected benefit obligation at the measurement date:
Discount rate	3.90%	4.49%	4.72%
Postretirement Benefits [Member]
Projected benefit obligation at the measurement date:
Discount rate	3.72%	4.36%	4.53%
Net periodic pension cost for the fiscal year:
Discount rate	4.36%	4.53%	4.13%
Pre Medicare [Member]
Postretirement benefit expense - Pre-Medicare:
Weighted average health care cost trend rate	6.94%	6.20%	7.50%
Trend rate graded down to ultimate rate	4.50%	4.50%	5.00%
Ultimate rate year	2025	2024	2021
Post Medicare [Member]
Postretirement benefit expense - Pre-Medicare:
Weighted average health care cost trend rate	8.07%	7.50%	7.00%
Trend rate graded down to ultimate rate	4.50%	4.50%	5.00%
Ultimate rate year	2025	2024	2021
Pension Plans [Member]
Projected benefit obligation at the measurement date:
Weighted average rate of compensation increase	0.00%	0.00%	0.00%
Net periodic pension cost for the fiscal year:
Weighted average expected long-term rate of return on plan assets	6.00%	6.50%	6.50%
Weighted average rate of compensation increase	0.00%	0.00%	0.00%
Pension Plans [Member] | Primary Plan [Member]
Projected benefit obligation at the measurement date:
Discount rate	3.80%	4.44%	4.72%
Pension Plans [Member] | Bargaining Plan [Member]
Projected benefit obligation at the measurement date:
Discount rate	3.90%	4.49%	4.72%
Pension Plans [Member] | Primary Plan and Bargaining Plan [Member]
Net periodic pension cost for the fiscal year:
Discount rate	4.44%	4.72%	4.32%