Segment Information - Schedule of Segment Information (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Segment Reporting Information [Line Items]
NET SALES:	$ 1,691.2	$ 1,577.6	$ 4,891.1	$ 4,627.2
NET SALES:	1,697.7	1,581.6	4,907.8	4,640.3
(LOSS) INCOME FROM OPERATIONS:	119.1	122.7	393.9	401.1
DEPRECIATION AND AMORTIZATION:	120.5	110.5	356.5	337.8
Corporate/Other/Eliminations
Segment Reporting Information [Line Items]
NET SALES:	48.1	40.3	118.2	107.8
(LOSS) INCOME FROM OPERATIONS:	(2.5)	(8.8)	(54.1)	(24.5)
DEPRECIATION AND AMORTIZATION:	6.1	5.1	16.9	15.6
Paperboard Mills | Operating Segments
Segment Reporting Information [Line Items]
NET SALES:	240.9	279.2	744.0	833.9
(LOSS) INCOME FROM OPERATIONS:	(34.4)	10.7	(92.6)	19.2
DEPRECIATION AND AMORTIZATION:	63.6	54.0	189.6	162.6
Americas Paperboard Packaging | Operating Segments
Segment Reporting Information [Line Items]
NET SALES:	1,214.8	1,091.1	3,491.9	3,176.6
(LOSS) INCOME FROM OPERATIONS:	140.5	112.2	492.4	363.1
DEPRECIATION AND AMORTIZATION:	40.2	39.9	120.3	124.5
Europe Paperboard Packaging | Operating Segments
Segment Reporting Information [Line Items]
NET SALES:	193.9	171.0	553.7	522.0
(LOSS) INCOME FROM OPERATIONS:	15.5	8.6	48.2	43.3
DEPRECIATION AND AMORTIZATION:	$ 10.6	$ 11.5	$ 29.7	$ 35.1