Goodwill and Intangible Assets - Goodwill (Details) - USD ($) $ in Millions		1 Months Ended	12 Months Ended
		Oct. 31, 2018	Dec. 31, 2019		Dec. 31, 2018
Goodwill [Line Items]
Beginning Balance			$ 917.3		$ 883.2	[1],[2]
Ending Balance			918.7		917.3
Sacramento Container and Englander
Goodwill [Line Items]
Acquisitions					34.1
Englander
Goodwill [Line Items]
Acquisitions	[3]		1.4
Packaging
Goodwill [Line Items]
Beginning Balance			862.1		828.0	[1],[2]
Ending Balance			863.5		862.1
Packaging | Sacramento Container and Englander
Goodwill [Line Items]
Acquisitions					34.1
Packaging | Englander
Goodwill [Line Items]
Acquisitions		$ 28.6	1.4	[3]
Paper
Goodwill [Line Items]
Beginning Balance			55.2		55.2	[1],[2]
Ending Balance			$ 55.2		$ 55.2

[1] During 2018, the Company recorded a $5.5 million adjustment to increase the goodwill balance for the Company’s October 2017 acquisition of Sacramento Container

[2] In connection with the October 2018 acquisition of Englander, the Company recorded $28.6 million of goodwill in the Packaging segment in 2018.

[3] During 2019, the Company recorded a $1.4 million adjustment to increase the goodwill balance for the Company’s October 2018 acquisition of Englander.