Basis of Presentation and New Accounting Pronouncements (Details) - USD ($) $ / shares in Units, $ in Thousands			3 Months Ended			9 Months Ended		12 Months Ended
	Oct. 04, 2018	Nov. 17, 2017	Sep. 29, 2018	Jun. 30, 2018	Sep. 23, 2017	Sep. 29, 2018	Sep. 23, 2017	Dec. 31, 2018
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating income			$ 56,150		$ 18,774	$ 168,630	$ 60,325
Other components of net periodic benefit costs			(2,159)		1,117	(6,553)	3,349
Gain on bargain purchase			$ 6,175		$ 0	$ 20,836	$ 0
Common stock, dividend declared (in dollars per share)			$ 0.07		$ 0.07	$ 0.21	$ 0.21
Subsequent Event
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Common stock, dividend declared (in dollars per share)	$ 0.07
Subsequent Event | Convertible Preferred Stock
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Convertible preferred stock, dividend declared (in dollars per share)	$ 2.00
Accounting Standards Update 2017-07
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating income					$ 1,000		$ 3,000
Other components of net periodic benefit costs					$ 1,000		3,000
Unrecognized components of employee benefit plans, net of tax
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Reclassification of tax effects from AOCI						$ 2,028	$ 3,353
Unrecognized components of employee benefit plans, net of tax | Scenario, Forecast | New Accounting Pronouncement, Early Adoption, Effect | Accounting Standards Update 2018-02
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Reclassification of tax effects from AOCI								$ 22,000
Tembec Inc.
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Gain on bargain purchase		$ 317,000		$ 15,000
Gain on bargain purchase, tax reserve				13,000
Gain on bargain purchase, contingent liability				$ 2,000
Disposal Group, Disposed of by Sale, Not Discontinued Operations | Resin Operations
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Sale of resin operations			$ 18,000			$ 18,000
Gain on sale of resin operations			$ 7,000