Revenue - Summary of Revenues Disaggregated by Product Line (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	[1]
Disaggregation Of Revenue [Line Items]
Revenue	$ 1,690.6	$ 1,536.5
Packaging
Disaggregation Of Revenue [Line Items]
Revenue	1,402.9	1,257.0
Paper
Disaggregation Of Revenue [Line Items]
Revenue	269.4	259.2
Corporate and Other
Disaggregation Of Revenue [Line Items]
Revenue	$ 18.3	$ 20.3

[1] Prior periods have not been adjusted under the modified retrospective method for Topic 606.