Segment Information - Segment Sales to External Customers by Product Line (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Revenue from External Customer [Line Items]
Segment sales to external customers	$ 7,730.3	$ 6,658.2	$ 6,964.3
Packaging
Revenue from External Customer [Line Items]
Segment sales to external customers	7,052.6	5,919.5	5,932.2
Paper
Revenue from External Customer [Line Items]
Segment sales to external customers	599.7	674.8	964.3
Operating Segments
Revenue from External Customer [Line Items]
Segment sales to external customers	7,730.3	6,658.2	6,964.3
Operating Segments | Packaging
Revenue from External Customer [Line Items]
Segment sales to external customers	7,052.6	5,919.5	5,932.2
Operating Segments | Paper
Revenue from External Customer [Line Items]
Segment sales to external customers	599.7	674.8	964.3
Operating Segments | Corporate and Other
Revenue from External Customer [Line Items]
Segment sales to external customers	$ 78.0	$ 63.9	$ 67.8