Employee Benefit Plans and Other Postretirement Benefits - Schedule of Pension Plan Asset Investments and Target Allocations (Details)	Dec. 31, 2023	Dec. 31, 2022
Fixed Income Securities
Defined Benefit Plan Disclosure [Line Items]
Percentage of Fair Value	72.00%	77.00%
Fixed Income Securities \| Packaging Corporation of America
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	72.00%
International Equity Securities
Defined Benefit Plan Disclosure [Line Items]
Percentage of Fair Value	15.00%	13.00%
U.S. Equity Securities
Defined Benefit Plan Disclosure [Line Items]
Percentage of Fair Value	11.00%	9.00%
Other Securities
Defined Benefit Plan Disclosure [Line Items]
Percentage of Fair Value	2.00%	1.00%
Other Securities \| Packaging Corporation of America
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	1.00%
Equity Securities \| Packaging Corporation of America
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	27.00%

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- Definition

Percentage of target investment allocation to total plan assets. Includes, but is not limited to, percentage on weighted-average basis if more than one plan.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 715
-SubTopic 20
-Name Accounting Standards Codification
-Section 55
-Paragraph 17
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480482/715-20-55-17

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 715
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (d)(i)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480506/715-20-50-1

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Percentage of actual investment allocation to total plan assets. Includes, but is not limited to, percentage on weighted-average basis if more than one plan.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 715
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (d)(i)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480506/715-20-50-1

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