Goodwill and Intangible Assets - Goodwill (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Goodwill [Line Items]
Beginning Balance	$ 883.2	$ 737.9
Ending Balance	917.3	883.2
Sacramento Container Corporation and TimBar and Columbus Container
Goodwill [Line Items]
Acquisitions		145.3
Sacramento Container and Englander
Goodwill [Line Items]
Acquisitions	34.1
Packaging
Goodwill [Line Items]
Beginning Balance	828.0	682.7
Ending Balance	862.1	828.0
Packaging | Sacramento Container Corporation and TimBar and Columbus Container
Goodwill [Line Items]
Acquisitions		145.3
Packaging | Sacramento Container and Englander
Goodwill [Line Items]
Acquisitions	34.1
Paper
Goodwill [Line Items]
Beginning Balance	55.2	55.2
Ending Balance	$ 55.2	$ 55.2