Segment Information - Selected Financial Information by Reportable Segment (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Segment Reporting Information [Line Items]
Net sales	$ 2,237.3	$ 1,879.9	$ 4,373.7	$ 3,687.0
Operating Income (Loss)	415.8	294.6	772.4	532.9
Non-operating pension income	3.6	5.0	7.3	9.8
Interest expense, net	(18.8)	(24.9)	(38.7)	(48.4)
Income before taxes	400.6	274.7	741.0	494.3
Trade
Segment Reporting Information [Line Items]
Net sales	2,237.3	1,879.9	4,373.7	3,687.0
Intersegment Eliminations
Segment Reporting Information [Line Items]
Net sales	(42.6)	(36.0)	(82.4)	(72.4)
Operating Segments
Segment Reporting Information [Line Items]
Net sales	2,237.3	1,879.9	4,373.7	3,687.0
Segment Reconciling Items
Segment Reporting Information [Line Items]
Net sales	(42.6)	(36.0)	(82.4)	(72.4)
Packaging
Segment Reporting Information [Line Items]
Net sales	2,066.9	1,718.5	4,031.3	3,342.1
Operating Income (Loss)	419.8	317.2	782.1	575.1
Packaging | Trade
Segment Reporting Information [Line Items]
Net sales	2,061.7	1,714.5	4,021.6	3,334.3
Packaging | Intersegment Eliminations
Segment Reporting Information [Line Items]
Net sales	5.2	4.0	9.7	7.8
Packaging | Operating Segments
Segment Reporting Information [Line Items]
Net sales	2,066.9	1,718.5	4,031.3	3,342.1
Paper
Segment Reporting Information [Line Items]
Net sales	149.8	142.3	303.3	306.8
Operating Income (Loss)	22.7	2.6	45.1	11.3
Paper | Trade
Segment Reporting Information [Line Items]
Net sales	149.8	142.3	303.3	306.7
Paper | Intersegment Eliminations
Segment Reporting Information [Line Items]
Net sales				0.1
Paper | Operating Segments
Segment Reporting Information [Line Items]
Net sales	149.8	142.3	303.3	306.8
Corporate and Other
Segment Reporting Information [Line Items]
Net sales	20.6	19.1	39.1	38.1
Operating Income (Loss)	(26.7)	(25.2)	(54.8)	(53.5)
Corporate and Other | Trade
Segment Reporting Information [Line Items]
Net sales	25.8	23.1	48.8	46.0
Corporate and Other | Intersegment Eliminations
Segment Reporting Information [Line Items]
Net sales	37.4	32.0	72.7	64.5
Corporate and Other | Operating Segments
Segment Reporting Information [Line Items]
Net sales	$ 63.2	$ 55.1	$ 121.5	$ 110.5