Divestitures and Impairments of Businesses (Narrative) (Details) € in Millions, R$ in Millions, $ in Millions	3 Months Ended					12 Months Ended
	Dec. 31, 2021 USD ($)	Sep. 30, 2021 USD ($)	Jun. 30, 2021 USD ($)	Mar. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2021 USD ($)	Dec. 31, 2021 EUR (€)	Dec. 31, 2020 USD ($)	Dec. 31, 2020 BRL (R$)	Dec. 31, 2019 USD ($)
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Distribution to Sylvamo Corporation						$ 130.0		$ 0.0		$ 0.0
Net (gains) losses on sales and impairments of businesses						(7.0)		465.0		205.0
Other comprehensive income (loss), foreign currency transaction and translation adjustment, before tax						2.0
Net (gains) losses on sales and impairments of businesses						358.0		(465.0)		(205.0)
Change in cumulative foreign currency translation adjustment (less tax of $0, $1 and $1)						69.0		$ 8.0		$ 116.0
Revolving Credit Facility [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Revolving credit facilities available	$ 1,500.0					$ 1,500.0
Minimum [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Debt instrument, interest rate, stated percentage	3.00%				3.00%	3.00%		3.00%		3.00%
Kwidzyn Mill [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Divestiture costs	$ 6.0
Net (gains) losses on sales and impairments of businesses		$ (350.0)
Olmuksan [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Net (gains) losses on sales and impairments of businesses			$ (9.0)	$ 2.0	$ 123.0
Discontinued Operations, Held-for-sale or Disposed of by Sale | Kwidzyn Mill [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Proceeds from Divestiture of Businesses						$ 794.0	€ 669.0
Net (gains) losses on sales and impairments of businesses		(404.0)
Net gains (losses) on sales and impairments of businesses, net of tax		350.0
Other comprehensive income (loss), foreign currency transaction and translation adjustment, before tax		(44.0)
Divestiture costs	9.0
Divestiture costs, net of taxes	6.0
Net (gains) losses on sales and impairments of businesses		360.0
Gain (Loss) on Sale of Assets and Asset Impairment Charges, net of tax		(394.0)
Discontinued Operations, Disposed of by Means Other than Sale, Spinoff [Member] | Printing Papers [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Proceeds from Issuance of Debt		1,500.0
Distribution to Sylvamo Corporation	130.0
Discontinued Operations, Disposed of by Means Other than Sale, Spinoff [Member] | Printing Papers [Member] | Term Loan "B" Facility [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Proceeds from Issuance of Debt		450.0
Discontinued Operations, Disposed of by Means Other than Sale, Spinoff [Member] | Printing Papers [Member] | Term Loan "F" Facility [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Proceeds from Issuance of Debt		520.0
Discontinued Operations, Disposed of by Means Other than Sale, Spinoff [Member] | Printing Papers [Member] | Revolving Credit Facility [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Proceeds from Lines of Credit		100.0
Revolving credit facilities available		450.0
Discontinued Operations, Disposed of by Means Other than Sale, Spinoff [Member] | Printing Papers [Member] | Unsecured Debt [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Proceeds from Issuance of Debt		$ 450.0
Discontinued Operations, Disposed of by Means Other than Sale, Spinoff [Member] | Printing Papers [Member] | Minimum [Member] | Unsecured Debt [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Debt instrument, interest rate, stated percentage		7.00%
Disposal Group, Disposed of by Sale, Not Discontinued Operations | Olmuksan [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Proceeds from Divestiture of Businesses						$ 81.0	€ 66.0
Net (gains) losses on sales and impairments of businesses	123.0		6.0
Net gains (losses) on sales and impairments of businesses, net of tax	$ (123.0)		$ 0.0
Sale of Stock, Percentage of Ownership before Transaction						90.38%	90.38%
Assets, Fair Value Disclosure					$ 79.0			$ 79.0
Change in cumulative foreign currency translation adjustment (less tax of $0, $1 and $1)				$ (2.0)
Disposal Group, Disposed of by Sale, Not Discontinued Operations | Brazilian Industrial Packaging
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Proceeds from Divestiture of Businesses								58.5	R$ 330.0
Proceeds to be received at closing								49.6	280.0
Deferred proceeds on disposal of business								$ 8.9	R$ 50.0
Number of containerboard mill to be sold								3	3
Number of box plants to be sold								4	4
Net (gains) losses on sales and impairments of businesses								$ 347.0
Net gains (losses) on sales and impairments of businesses, net of tax								340.0
Other comprehensive income (loss), foreign currency transaction and translation adjustment, before tax								327.0
Impairment of long-lived assets to be disposed of								$ 20.0