Goodwill and Other Intangible Assets - Changes in carrying value of goodwill (Details) - USD ($)	9 Months Ended	12 Months Ended
	Sep. 30, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Goodwill [Roll Forward]
Goodwill, net, beginning balance	$ 85,300,000	$ 84,000,000.0	$ 85,300,000
Adjustment of goodwill acquired in the Coldenhove Acquisition			1,100,000
Impairment related to the Brattleboro mill and associated office and research facilities			(100,000)
Foreign currency translation		(900,000)	(2,300,000)
Realignment of Other segment		0
Goodwill, net, ending balance		$ 83,100,000	84,000,000.0	$ 85,300,000
Minimum
Goodwill [Line Items]
Intangible asset useful lives		10 years
Maximum
Goodwill [Line Items]
Intangible asset useful lives		15 years
Technical Products
Goodwill [Roll Forward]
Goodwill gross, beginning balance	128,300,000	$ 124,900,000	128,300,000
Accumulated Impairment Loss, beginning of period	(49,600,000)	(47,400,000)	(49,600,000)
Goodwill, net, beginning balance	78,700,000	77,500,000	78,700,000
Adjustment of goodwill acquired in the Coldenhove Acquisition			1,100,000
Foreign currency translation gross impact		(1,900,000)	(4,500,000)
Foreign currency translation, accumulated impairment losses impact		1,000,000.0	2,200,000
Foreign currency translation		(900,000)	(2,300,000)
Realignment of Other segment, gross impact		400,000
Realignment of Other segment, accumulated impairment		(100,000)
Realignment of Other segment		300,000
Goodwill gross, ending balance		123,400,000	124,900,000	128,300,000
Accumulated Impairment Loss, end of period		(46,500,000)	(47,400,000)	(49,600,000)
Goodwill, net, ending balance		76,900,000	77,500,000	78,700,000
Adjustment to goodwill			1,100,000
Fine Paper and Packaging
Goodwill [Roll Forward]
Goodwill gross, beginning balance	6,200,000	6,200,000	6,200,000
Goodwill, net, beginning balance	6,200,000	6,200,000	6,200,000
Goodwill gross, ending balance		6,200,000	6,200,000	6,200,000
Goodwill, net, ending balance		6,200,000	6,200,000	6,200,000
Other
Goodwill [Roll Forward]
Goodwill gross, beginning balance	400,000	400,000	400,000
Accumulated Impairment Loss, beginning of period		(100,000)
Goodwill, net, beginning balance	400,000	300,000	400,000
Impairment related to the Brattleboro mill and associated office and research facilities			(100,000)
Realignment of Other segment, gross impact		(400,000)
Realignment of Other segment, accumulated impairment		100,000
Realignment of Other segment		(300,000)
Goodwill gross, ending balance		0	400,000	400,000
Accumulated Impairment Loss, end of period		0	(100,000)
Goodwill, net, ending balance		0	300,000	400,000
Goodwill Other Than Brattleboro Mill
Goodwill [Roll Forward]
Impairment related to the Brattleboro mill and associated office and research facilities		$ 0	0	0
W.A. Sanders Coldenhove Holding B.V.
Goodwill [Roll Forward]
Goodwill, net, beginning balance	10,000,000.0		10,000,000.0
Goodwill, net, ending balance				$ 10,000,000.0
Adjustment to goodwill	$ 1,100,000
Brattleboro Mill and Associated Research and Office Facilities
Goodwill [Roll Forward]
Impairment related to the Brattleboro mill and associated office and research facilities			$ (100,000)