Contingent Liabilities - Other (Details) - USD ($)	1 Months Ended		3 Months Ended				9 Months Ended
	Dec. 31, 2014	Sep. 30, 2013	Sep. 25, 2016	Jun. 26, 2016	Sep. 27, 2015	Mar. 29, 2015	Sep. 25, 2016	Sep. 27, 2015	Jun. 14, 2016
Loss Contingencies [Line Items]
Multiemployer pension plan withdrawal (income)/expense			$ (4,971,000)	$ 11,700,000	$ 0	$ 4,700,000	$ 6,730,000	$ 4,697,000
Threatened Litigation
Loss Contingencies [Line Items]
Demand for payment	$ 34,000,000	$ 26,000,000
Decline in contributions, percent (more than)		70.00%
Payments made in accordance with ERISA			10,800,000				10,800,000
Payments made in current period							2,700,000
Overstatement of pension withdrawal obligation									$ 7,500,000
Partial pension withdrawal arbitration liability			10,500,000				10,500,000
Partial pension withdrawal contingent loss, minimum			0				0
Partial pension withdrawal contingent loss, maximum			$ 10,000,000				$ 10,000,000