Unaudited Quarterly Data (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Effect of Fourth Quarter Events [Line Items]
Net sales	$ 244.0	$ 245.1	$ 248.7	$ 242.1	$ 220.5	$ 232.9	$ 246.0	$ 242.1	$ 979.9	$ 941.5	$ 887.7
Gross Profit	45.1	48.0	53.6	52.0	46.5	49.2	60.0	58.8	198.7	214.5	195.4
Operating Income	19.1	29.0	29.2	27.0	21.9	26.9	33.9	31.4	104.3	114.1	101.4
Income from continuing operations	$ 18.9	$ 18.8	$ 25.0	$ 17.6	$ 16.4	$ 16.4	$ 21.4	$ 19.2	$ 80.3	$ 73.4	$ 60.5
Earnings (Loss) Per Common Share
Basic (in dollar per share)	$ 1.11	$ 1.11	$ 1.47	$ 1.04	$ 0.97	$ 0.97	$ 1.26	$ 1.13	$ 4.74	$ 4.33	$ 3.58
Diluted (in dollars per share)	$ 1.10	$ 1.10	$ 1.46	$ 1.03	$ 0.95	$ 0.95	$ 1.24	$ 1.11	$ 4.68	$ 4.26	$ 3.53
Undistributed foreign earnings	$ 0.0				$ (4.4)				$ 0.0	$ (4.4)
Insurance recoveries		$ (3.2)							(3.2)	0.0	$ 0.0
Business combination, acquisition related costs	0.6	0.7
Acquisition/integration/restructuring costs									1.3	7.0	6.5
Pension plan settlement charge	0.4	$ 0.2							$ 0.6	0.8	0.0
Tax adjustments, settlements, and unusual provisions	$ 5.9
FiberMark
Earnings (Loss) Per Common Share
Acquisition/integration/restructuring costs										$ 4.3	$ 5.3
Federal Ministry of Finance, Germany
Earnings (Loss) Per Common Share
Undistributed foreign earnings			$ 4.1