Benefit Plans - Significant Assumptions Used (Detail)		12 Months Ended
		Dec. 30, 2018	Dec. 31, 2017	Jan. 01, 2017
Net periodic pension cost for the fiscal year:
Weighted average expected long-term rate of return on plan assets	[1]	5.00%
Primary Plan [Member]
Net periodic pension cost for the fiscal year:
Weighted average expected long-term rate of return on plan assets		5.00%
Bargaining Plan [Member]
Net periodic pension cost for the fiscal year:
Weighted average expected long-term rate of return on plan assets		5.25%
Postretirement Benefits [Member]
Projected benefit obligation at the measurement date:
Discount rate		4.41%	3.72%	4.36%
Net periodic pension cost for the fiscal year:
Discount rate		3.72%	4.36%	4.53%
Pre Medicare [Member]
Postretirement benefit expense - Pre-Medicare:
Weighted average healthcare cost trend rate		7.82%	6.94%	6.20%
Trend rate graded down to ultimate rate		4.50%	4.50%	4.50%
Ultimate rate year		2025	2025	2024
Post Medicare [Member]
Postretirement benefit expense - Pre-Medicare:
Weighted average healthcare cost trend rate		7.74%	8.07%	7.50%
Trend rate graded down to ultimate rate		4.50%	4.50%	4.50%
Ultimate rate year		2025	2025	2024
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	[2]	6.00%	6.00%	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		4.47%	3.80%	4.44%
Net periodic pension cost for the fiscal year:
Discount rate		3.80%	4.44%	4.72%
Pension Plans [Member] | Bargaining Plan [Member]
Projected benefit obligation at the measurement date:
Discount rate		4.63%	3.90%	4.49%
Net periodic pension cost for the fiscal year:
Discount rate		3.90%	4.49%	4.72%

[1] The weighted average expected long-term rate of return of plan assets is 5.0% for the Primary Plan and 5.25% for the Bargaining Plan.

[2] The weighted average expected long-term rate of return, which is used in computing net periodic pension cost, reflects an estimate of long-term future returns for the pension plan assets net of expenses. The estimate is primarily a function of the asset classes, equities versus fixed income, in which the pension plan assets are invested and the analysis of past performance of these asset classes over a long period of time. The analysis includes expected long-term inflation and the risk premiums associated with equity investments and fixed income investments.