Contingent Liabilities - Restricted Cash (Details) - USD ($)	1 Months Ended			3 Months Ended				9 Months Ended
	Jul. 29, 2016	Dec. 31, 2014	Sep. 30, 2013	Sep. 24, 2017	Dec. 25, 2016	Sep. 25, 2016	Jun. 26, 2016	Sep. 24, 2017	Sep. 25, 2016
Loss Contingencies [Line Items]
Restricted cash				$ 17,900,000	$ 24,900,000			$ 17,900,000
Amount paid related to Revised Assessment	$ (5,000,000)			0		$ 4,971,000	$ (11,700,000)	0	$ (6,730,000)
Threatened Litigation
Loss Contingencies [Line Items]
Demand for payment		$ 34,000,000	$ 26,000,000
Decline in contributions, percent (more than)			70.00%
Payments related to Initial Assessment								14,400,000
Amount recognized as expense in the period				100,000		$ 4,500,000		300,000	$ 10,600,000
Partial pension withdrawal arbitration liability				7,300,000				7,300,000
Minimum | Threatened Litigation
Loss Contingencies [Line Items]
Estimate of possible loss				0				0
Maximum | Threatened Litigation
Loss Contingencies [Line Items]
Estimate of possible loss				10,000,000				$ 10,000,000
Discontinued Operations
Loss Contingencies [Line Items]
Litigation settlement charge				800,000	3,700,000
Litigation settlement charge, net of tax				$ 500,000	$ 2,300,000