Sale of Battleboro Mill and Impairment Loss (Details) - USD ($) $ in Millions	3 Months Ended			9 Months Ended	12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Dec. 31, 2018	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Disposal Groups
Impairment loss	$ (2.9)	$ 2.0		$ 32.0	$ 31.1	$ 0.0	$ 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			$ 32.0		31.1
Cash proceeds from sale of mill	$ 5.0			$ 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