Income Taxes - Net Deferred Tax Assets and Liabilities (Details) - USD ($)	12 Months Ended
	Dec. 27, 2020	Dec. 29, 2019
Deferred tax assets
Retirement, postemployment and deferred compensation plans	$ 103,433,000	$ 113,306,000
Accruals for other employee benefits, compensation, insurance and other	25,899,000	25,543,000
Net operating losses	1,510,000	1,289,000
Operating lease liabilities	16,648,000	16,746,000
Other	32,664,000	27,042,000
Gross deferred tax assets	180,154,000	183,926,000
Valuation allowance	(293,000)	0
Net deferred tax assets	179,861,000	183,926,000
Deferred tax liabilities
Property, plant and equipment	41,832,000	39,494,000
Intangible assets	7,652,000	7,596,000
Operating lease right-of-use assets	14,196,000	14,309,000
Other	16,663,000	7,298,000
Gross deferred tax liabilities	80,343,000	68,697,000
Net deferred tax asset	$ 99,518,000	$ 115,229,000
Valuation allowance, period for recoverability measurement (in years)	3 years