Segment and Geographical Information - Net Sales and Operating Income (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 28, 2019	Jun. 29, 2019	Mar. 30, 2019	Dec. 31, 2018	Sep. 29, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Product Information [Line Items]
Net Sales	$ 467,970	$ 416,129	$ 450,233	$ 441,060	$ 481,345	$ 501,298	$ 494,860	$ 479,491	$ 1,775,392	$ 1,956,994	$ 940,416
Operating Income	$ (31,635)	$ (8,564)	$ (15,320)	$ (27,599)	$ 16,783	$ 42,940	$ 52,859	$ 35,233	(83,118)	147,815	58,980
Eliminations
Product Information [Line Items]
Net Sales									(65,667)	(70,221)	(7,394)
High Purity Cellulose | Operating Segments
Product Information [Line Items]
Net Sales									1,126,987	1,192,389	866,861
Operating Income									6,588	112,308	120,356
Forest Products | Operating Segments
Product Information [Line Items]
Net Sales									299,113	355,660	33,945
Operating Income									(30,904)	24,850	(4)
Paperboard | Operating Segments
Product Information [Line Items]
Operating Income									4,120	4,392	(899)
Pulp & Newsprint | Operating Segments
Product Information [Line Items]
Net Sales									214,972	282,300	28,129
Operating Income									1,658	71,899	1,683
Corporate | Operating Segments
Product Information [Line Items]
Operating Income									(64,580)	(65,634)	(62,156)
Cellulose Specialties | High Purity Cellulose | Operating Segments
Product Information [Line Items]
Net Sales									765,077	831,805	661,760
Commodity Products | High Purity Cellulose | Operating Segments
Product Information [Line Items]
Net Sales									279,527	243,711	183,208
Other sales | High Purity Cellulose | Operating Segments
Product Information [Line Items]
Net Sales									82,383	116,873	21,893
Other sales | Forest Products | Operating Segments
Product Information [Line Items]
Net Sales									68,753	71,242	8,065
Lumber | Forest Products | Operating Segments
Product Information [Line Items]
Net Sales									230,360	284,418	25,880
Paperboard | Paperboard | Operating Segments
Product Information [Line Items]
Net Sales									199,987	196,866	18,875
Pulp | Pulp & Newsprint | Operating Segments
Product Information [Line Items]
Net Sales									127,784	169,025	17,553
Newsprint | Pulp & Newsprint | Operating Segments
Product Information [Line Items]
Net Sales									$ 87,188	$ 113,275	$ 10,576