Income Taxes - Net Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 27, 2015	Dec. 28, 2014
Deferred tax assets
Retirement, postemployment and deferred compensation plans	$ 309,711	$ 320,174
Accruals for other employee benefits, compensation, insurance and other	32,731	42,294
Accounts receivable allowances	1,690	1,746
Net operating losses	38,703	46,726
Other	44,099	41,186
Gross deferred tax assets	426,934	452,126
Valuation allowance	(36,204)	(41,136)
Net deferred tax assets	390,730	410,990
Deferred tax liabilities
Property, plant and equipment	57,065	64,056
Intangible assets	10,790	11,607
Investments in joint ventures	11,694	13,971
Other	2,039	5,129
Gross deferred tax liabilities	81,588	94,763
Net deferred tax asset	309,142	316,227
Deferred tax asset – current	0	63,640
Deferred tax asset – long-term	$ 309,142	$ 252,587
Valuation allowance, period for recoverability measurement	3 years