Segment Information - Analysis of Operations by Reportable Segment (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Segment Reporting Information [Line Items]
Revenue	$ 8,478.0	$ 7,730.3	$ 6,658.2
Operating Income (Loss)	1,420.7	1,241.4	723.9
Non-operating pension income and expense	14.5	19.7	2.3
Interest expense, net	(70.4)	(152.4)	(93.5)
Income before taxes	1,364.8	1,108.7	632.7
Depreciation, Amortization, and Depletion	456.8	417.5	410.0
Capital Expenditures	824.2	605.1	421.2
Assets	8,003.8	7,836.8	7,433.2
Trade
Segment Reporting Information [Line Items]
Revenue	8,478.0	7,730.3	6,658.2
Intersegment Eliminations
Segment Reporting Information [Line Items]
Revenue	(168.2)	(152.4)	(149.2)
Operating Income (Loss)
Depreciation, Amortization, and Depletion
Capital Expenditures
Assets
Intersegment Eliminations | Trade
Segment Reporting Information [Line Items]
Revenue		0.0	0.0
Operating Segments
Segment Reporting Information [Line Items]
Revenue	8,478.0	7,730.3	6,658.2
Segment Reconciling Items
Segment Reporting Information [Line Items]
Revenue		(152.4)	(149.2)
Operating Income (Loss)
Depreciation, Amortization, and Depletion
Capital Expenditures
Assets
Segment Reconciling Items | Trade
Segment Reporting Information [Line Items]
Revenue
Packaging
Segment Reporting Information [Line Items]
Revenue	7,780.7	7,052.6	5,919.5
Operating Income (Loss)	1,423.7	1,306.0	829.5
Depreciation, Amortization, and Depletion	420.2	381.0	365.2
Capital Expenditures	753.5	562.5	394.8
Assets	6,986.5	6,603.3	5,744.0
Packaging | Trade
Segment Reporting Information [Line Items]
Revenue	7,760.7	7,036.2	5,901.7
Packaging | Intersegment Eliminations
Segment Reporting Information [Line Items]
Revenue	20.0	16.4	17.8
Packaging | Operating Segments
Segment Reporting Information [Line Items]
Revenue	7,780.7	7,052.6	5,919.5
Paper
Segment Reporting Information [Line Items]
Revenue	622.1	599.7	674.8
Operating Income (Loss)	103.0	39.1	(20.0)
Depreciation, Amortization, and Depletion	26.1	27.4	36.5
Capital Expenditures	14.1	30.1	20.1
Assets	403.1	398.9	497.2
Paper | Trade
Segment Reporting Information [Line Items]
Revenue	622.1	599.6	674.7
Paper | Intersegment Eliminations
Segment Reporting Information [Line Items]
Revenue		0.1	0.1
Paper | Operating Segments
Segment Reporting Information [Line Items]
Revenue	622.1	599.7	674.8
Corporate and Other
Segment Reporting Information [Line Items]
Revenue	75.2	78.0	63.9
Operating Income (Loss)	(106.0)	(103.7)	(85.6)
Depreciation, Amortization, and Depletion	10.5	9.1	8.3
Capital Expenditures	56.6	12.5	6.3
Assets	614.2	834.6	1,192.0
Corporate and Other | Trade
Segment Reporting Information [Line Items]
Revenue	95.2	94.5	81.8
Corporate and Other | Intersegment Eliminations
Segment Reporting Information [Line Items]
Revenue	148.2	135.9	131.3
Corporate and Other | Operating Segments
Segment Reporting Information [Line Items]
Revenue	$ 243.4	$ 230.4	$ 213.1