Goodwill And Intangible Assets (Goodwill And Changes In Carrying Amount Of Goodwill By Operating Segment) (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2016	Dec. 31, 2015
Goodwill [Roll Forward]
Balance, beginning of period	$ 597.7	$ 590.6
Acquisitions of businesses	36.9	8.6
Currency translation and other adjustments	0.2	(1.5)
Balance, end of period	634.8	597.7
Specialty Engineered Materials
Goodwill [Roll Forward]
Balance, beginning of period	98.0	99.4
Acquisitions of businesses	36.9	0.0
Currency translation and other adjustments	0.2	(1.4)
Balance, end of period	135.1	98.0
Color, Additives and Inks
Goodwill [Roll Forward]
Balance, beginning of period	342.2	333.7
Acquisitions of businesses	0.0	8.6
Currency translation and other adjustments	0.0	(0.1)
Balance, end of period	342.2	342.2
Designed Structures and Solutions
Goodwill [Roll Forward]
Balance, beginning of period	144.7	144.7
Acquisitions of businesses	0.0	0.0
Currency translation and other adjustments	0.0	0.0
Balance, end of period	144.7	144.7
Performance Products and Solutions
Goodwill [Roll Forward]
Balance, beginning of period	11.2	11.2
Acquisitions of businesses	0.0	0.0
Currency translation and other adjustments	0.0	0.0
Balance, end of period	11.2	11.2
PolyOne Distribution
Goodwill [Roll Forward]
Balance, beginning of period	1.6	1.6
Acquisitions of businesses	0.0	0.0
Currency translation and other adjustments	0.0	0.0
Balance, end of period	$ 1.6	$ 1.6