Benefit Plans - Significant Assumptions Used (Detail)		12 Months Ended
		Dec. 29, 2019	Dec. 30, 2018	Dec. 31, 2017
Net periodic pension cost for the fiscal year:
Weighted average expected long-term rate of return of plan assets	[1]	5.50%
Primary Plan [Member]
Net periodic pension cost for the fiscal year:
Weighted average expected long-term rate of return of plan assets		5.50%
Bargaining Plan [Member]
Net periodic pension cost for the fiscal year:
Weighted average expected long-term rate of return of plan assets		6.25%
Pension Plans [Member] | Primary Plan [Member]
Projected benefit obligation at the measurement date:
Discount rate		3.36%	4.47%	3.80%
Net periodic pension cost for the fiscal year:
Discount rate		4.47%	3.80%	4.44%
Weighted average expected long-term rate of return of plan assets	[2]	5.00%	6.00%	6.00%
Pension Plans [Member] | Bargaining Plan [Member]
Projected benefit obligation at the measurement date:
Discount rate		3.61%	4.63%	3.90%
Net periodic pension cost for the fiscal year:
Discount rate		4.63%	3.90%	4.49%
Weighted average expected long-term rate of return of plan assets	[2]	5.25%	6.00%	6.00%
Postretirement Benefits [Member]
Projected benefit obligation at the measurement date:
Discount rate		3.32%	4.41%	3.72%
Net periodic pension cost for the fiscal year:
Discount rate		4.41%	3.72%	4.36%
Pre Medicare [Member]
Postretirement benefit expense - Pre-Medicare:
Weighted average healthcare cost trend rate		7.13%	7.82%	6.94%
Trend rate graded down to ultimate rate		4.50%	4.50%	4.50%
Ultimate rate year		2026	2025	2025
Post Medicare [Member]
Postretirement benefit expense - Pre-Medicare:
Weighted average healthcare cost trend rate		7.11%	7.74%	8.07%
Trend rate graded down to ultimate rate		4.50%	4.50%	4.50%
Ultimate rate year		2026	2025	2025

[1] The weighted average expected long-term rate of return of plan assets is 5.50% for the Primary Plan and 6.25% 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.