Segment Information (Schedule of Segment Information) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Segment Reporting Information [Line Items]
Sales	$ 883.0	$ 818.5	$ 2,699.4	$ 2,429.3
Operating Income	70.5	65.7	226.7	225.7
Assets	2,785.3		2,785.3		$ 2,705.3
Color, Additives and Inks
Segment Reporting Information [Line Items]
Sales	259.1	232.6	800.9	657.2
Specialty Engineered Materials
Segment Reporting Information [Line Items]
Sales	152.6	143.9	455.9	436.6
Performance Products and Solutions
Segment Reporting Information [Line Items]
Sales	154.0	155.1	495.5	480.6
PolyOne Distribution
Segment Reporting Information [Line Items]
Sales	317.3	286.9	947.1	854.9
Operating Segments | Color, Additives and Inks
Segment Reporting Information [Line Items]
Sales	261.0	235.1	805.6	670.6
Operating Income	41.1	36.4	128.5	110.1
Assets	1,240.9		1,240.9		1,146.8
Operating Segments | Specialty Engineered Materials
Segment Reporting Information [Line Items]
Sales	166.7	156.3	495.3	474.1
Operating Income	18.9	17.6	60.1	60.1
Assets	607.0		607.0		545.1
Operating Segments | Performance Products and Solutions
Segment Reporting Information [Line Items]
Sales	176.0	175.7	558.9	543.6
Operating Income	16.3	17.8	61.6	62.2
Assets	277.5		277.5		275.8
Operating Segments | PolyOne Distribution
Segment Reporting Information [Line Items]
Sales	321.8	291.1	960.6	868.0
Operating Income	17.6	18.6	54.5	57.5
Assets	277.0		277.0		250.9
Corporate and eliminations
Segment Reporting Information [Line Items]
Sales	(42.5)	(39.7)	(121.0)	(127.0)
Operating Income	(23.4)	$ (24.7)	(78.0)	$ (64.2)
Assets	$ 382.9		$ 382.9		$ 486.7