Segment Information - Analysis of Operations by Reportable Segment (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Segment Reporting Information [Line Items]
Revenue	$ 7,730.3	$ 6,658.2	$ 6,964.3
Operating Income (Loss)	1,241.4	723.9	1,053.7
Non-operating pension income and expense	19.7	2.3	(7.9)
Interest expense, net	(152.4)	(93.5)	(128.8)
Income before taxes	1,108.7	632.7	917.0
Depreciation, Amortization, and Depletion	417.5	410.0	387.5
Capital Expenditures	605.1	421.2	399.5
Assets	7,836.8	7,433.2	7,235.8
Trade
Segment Reporting Information [Line Items]
Revenue	7,730.3	6,658.2	6,964.3
Intersegment Eliminations
Segment Reporting Information [Line Items]
Revenue	(152.4)	(149.2)	(160.2)
Operating Segments
Segment Reporting Information [Line Items]
Revenue	7,730.3	6,658.2	6,964.3
Segment Reconciling Items
Segment Reporting Information [Line Items]
Revenue	(152.4)	(149.2)	(160.2)
Packaging
Segment Reporting Information [Line Items]
Revenue	7,052.6	5,919.5	5,932.2
Operating Income (Loss)	1,306.0	829.5	963.4
Depreciation, Amortization, and Depletion	381.0	365.2	342.8
Capital Expenditures	562.5	394.8	367.4
Assets	6,603.3	5,744.0	5,491.5
Packaging | Trade
Segment Reporting Information [Line Items]
Revenue	7,036.2	5,901.7	5,905.1
Packaging | Intersegment Eliminations
Segment Reporting Information [Line Items]
Revenue	16.4	17.8	27.1
Packaging | Operating Segments
Segment Reporting Information [Line Items]
Revenue	7,052.6	5,919.5	5,932.2
Paper
Segment Reporting Information [Line Items]
Revenue	599.7	674.8	964.3
Operating Income (Loss)	(39.1)	(20.0)	175.4
Depreciation, Amortization, and Depletion	27.4	36.5	37.7
Capital Expenditures	30.1	20.1	23.8
Assets	398.9	497.2	791.4
Paper | Trade
Segment Reporting Information [Line Items]
Revenue	599.6	674.7	964.3
Paper | Intersegment Eliminations
Segment Reporting Information [Line Items]
Revenue	0.1
Paper | Operating Segments
Segment Reporting Information [Line Items]
Revenue	599.7	674.8	964.3
Corporate and Other
Segment Reporting Information [Line Items]
Revenue	78.0	63.9	67.8
Operating Income (Loss)	(103.7)	(85.6)	(85.1)
Depreciation, Amortization, and Depletion	9.1	8.3	7.0
Capital Expenditures	12.5	6.3	8.3
Assets	834.6	1,192.0	952.9
Corporate and Other | Trade
Segment Reporting Information [Line Items]
Revenue	94.5	81.8	94.9
Corporate and Other | Intersegment Eliminations
Segment Reporting Information [Line Items]
Revenue	135.9	131.3	133.1
Corporate and Other | Operating Segments
Segment Reporting Information [Line Items]
Revenue	$ 230.4	$ 213.1	$ 228.0