Contingent Liabilities - Other (Details) - USD ($)	1 Months Ended			3 Months Ended			6 Months Ended
	Jul. 29, 2016	Dec. 31, 2014	Sep. 30, 2013	Jun. 25, 2017	Dec. 25, 2016	Jun. 26, 2016	Jun. 25, 2017	Jun. 26, 2016
Loss Contingencies [Line Items]
Amount paid related to Revised Assessment	$ 5,000,000			$ 0		$ 11,701,000	$ 0	$ 11,701,000
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							13,500,000
Amount recognized as expense in the period				100,000		$ 13,300,000	200,000	$ 15,100,000
Partial pension withdrawal arbitration liability				8,100,000			8,100,000
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					$ 3,700,000