Business Combinations - Additional Disclosures (Details)					3 Months Ended	12 Months Ended
	Aug. 01, 2019 USD ($) mill facility	Sep. 30, 2018 USD ($) facility	Jun. 12, 2018 USD ($) facility	Jan. 01, 2018 USD ($) facility	Mar. 31, 2019 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Business Acquisition [Line Items]
Number of converting facilities acquired | facility	2
Number of mills acquired | mill	1
Identifiable intangible assets acquired	$ 6,500,000
Net assets acquired	38,500,000
Goodwill	$ 7,500,000					$ 1,477,900,000	$ 1,460,600,000	$ 1,323,000,000.0
Net sales from business acquisition						31,200,000
Net income from business acquisition						2,000,000.0
Payments to acquire businesses						54,500,000	89,400,000	189,400,000
Assets						7,289,900,000	7,059,200,000	4,863,000,000.0
Artistic Carton Company
Business Acquisition [Line Items]
Number of converting facilities acquired | facility	2
Number of mills acquired | mill	1
Payment to acquire business	$ 52,500,000
NACP Combination
Business Acquisition [Line Items]
Net sales from business acquisition							134,700,000
Net income from business acquisition							1,407,100,000
Debt assumed in acquisition							660,000,000
Total Purchase Consideration					$ 1,800,000,000
Percentage of projected tax benefits				50.00%
Expected tax deductible portion of goodwill acquired				$ 0
NACP Combination | Paperboard Mills
Business Acquisition [Line Items]
Number of mills | facility				2
Assets							1,500,000,000
NACP Combination | NACP | UNITED STATES
Business Acquisition [Line Items]
Number of converting facilities | facility				3
NACP Combination | Europe Paperboard Packaging | UNITED KINGDOM
Business Acquisition [Line Items]
Number of converting facilities | facility				1
NACP Combination | Products And Services, Transition Services | International Paper Company
Business Acquisition [Line Items]
Payments to Suppliers						100,000	22,000,000.0
NACP Combination | Product And Services, Fiber Procurement And Corrugated Products | International Paper Company
Business Acquisition [Line Items]
Payments to Suppliers						12,400,000	15,900,000
NACP Combination | Product And Services, Wood | International Paper Company
Business Acquisition [Line Items]
Payments to Suppliers						229,100,000	194,000,000
NACP Combination | Products And Services, Ink Supply | International Paper Company
Business Acquisition [Line Items]
Payments to Suppliers						26,600,000	28,500,000
NACP Combination | Products And Services, Unrelated To Agreements | International Paper Company
Business Acquisition [Line Items]
Payments to Suppliers						$ 4,000,000	6,000,000
Leticia Corporation
Business Acquisition [Line Items]
Number of converting facilities acquired | facility		2
Net sales from business acquisition							42,400,000
Payments to acquire businesses		$ 95,000,000
Adjustments to property, plant and equipment					$ (5,000,000)
PFP, LLC And PFP Dallas Converting, LLC
Business Acquisition [Line Items]
Number of converting facilities acquired | facility			2
Net sales from business acquisition							1,400,000
Payments to acquire businesses			$ 34,000,000
Americas Paperboard Packaging | Paperboard Mills
Business Acquisition [Line Items]
Assets							600,000,000
Acquisitions in 2017 [Member]
Business Acquisition [Line Items]
Payments to acquire businesses								$ 189,000,000
NACP Combination And PFP Acquisition
Business Acquisition [Line Items]
Payment to acquire business							1,200,800,000
Identifiable intangible assets acquired							150,100,000
Net assets acquired							1,713,000,000.0
Goodwill							147,800,000
Total Purchase Consideration							1,860,800,000
Adjustments to property, plant and equipment							32,000,000.0
NACP Combination And PFP Acquisition | Previously Reported
Business Acquisition [Line Items]
Payment to acquire business							1,241,700,000
Identifiable intangible assets acquired							136,600,000
Net assets acquired							1,674,400,000
Goodwill							227,300,000
Total Purchase Consideration							$ 1,901,700,000