Segment Information - Schedule of Segment Information (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Segment Reporting Information [Line Items]
Net sales	$ 1,605.3	$ 1,548.1	$ 3,199.9	$ 3,049.7
Net Sales	1,611.0	1,552.8	3,210.1	3,058.7
Income (Loss) from Operations	114.8	144.4	274.8	278.4
Depreciation and Amortization	122.4	110.2	236.0	227.3
Corporate/Other/Eliminations
Segment Reporting Information [Line Items]
Net Sales	39.7	33.7	70.1	67.5
Income (Loss) from Operations	(27.7)	(8.9)	(51.6)	(15.7)
Depreciation and Amortization	5.4	5.1	10.8	10.5
Paperboard Mills | Operating Segments
Segment Reporting Information [Line Items]
Net sales	234.6	279.2	503.1	554.7
Income (Loss) from Operations	(35.3)	12.5	(58.2)	8.5
Depreciation and Amortization	67.0	52.4	126.0	108.6
Americas Paperboard Packaging | Operating Segments
Segment Reporting Information [Line Items]
Net sales	1,153.7	1,062.7	2,277.1	2,085.5
Income (Loss) from Operations	157.1	125.3	351.9	250.9
Depreciation and Amortization	40.7	40.9	80.1	84.6
Europe Paperboard Packaging | Operating Segments
Segment Reporting Information [Line Items]
Net sales	183.0	177.2	359.8	351.0
Income (Loss) from Operations	20.7	15.5	32.7	34.7
Depreciation and Amortization	$ 9.3	$ 11.8	$ 19.1	$ 23.6