Benefit Plans - Significant Assumptions Used, Pension Plans (Detail) - Pension Plans	12 Months Ended
	Dec. 31, 2020	Dec. 29, 2019	Dec. 30, 2018
Primary Plan
Projected benefit obligation at the measurement date:
Discount rate	2.66%	3.36%	4.47%
Net periodic pension cost for the fiscal year:
Discount rate	3.36%	4.47%	3.80%
Weighted average expected long-term rate of return of plan assets	5.50%	5.00%	6.00%
Bargaining Plan
Projected benefit obligation at the measurement date:
Discount rate	3.12%	3.61%	4.63%
Net periodic pension cost for the fiscal year:
Discount rate	3.61%	4.63%	3.90%
Weighted average expected long-term rate of return of plan assets	6.25%	5.25%	6.00%