Sale of Battleboro Mill and Impairment Loss (Details) - USD ($) $ in Millions	3 Months Ended			12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Disposal Groups
Impairment loss	$ (2.9)	$ 2.0	$ 32.0	$ 0.0	$ 31.1	$ 0.0
Brattleboro Mill and Associated Research and Office Facilities | Disposal Group, Held-for-sale or Disposed of by Sale, Not Discontinued Operations
Disposal Groups
Impairment loss					31.1
Cash proceeds from sale of mill	$ 5.0				5.0
Fine Paper and Packaging | Brattleboro Mill and Associated Research and Office Facilities | Disposal Group, Held-for-sale or Disposed of by Sale, Not Discontinued Operations
Disposal Groups
Impairment loss					24.4
Technical Products | Brattleboro Mill and Associated Research and Office Facilities | Disposal Group, Held-for-sale or Disposed of by Sale, Not Discontinued Operations
Disposal Groups
Impairment loss					1.1
Other | Brattleboro Mill and Associated Research and Office Facilities | Disposal Group, Held-for-sale or Disposed of by Sale, Not Discontinued Operations
Disposal Groups
Impairment loss					$ 5.6