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Employee Benefit Plans and Other Postretirement Benefits - Schedule of Pension Plan Asset Investments and Target Allocations (Details) | Dec. 31, 2023 | Dec. 31, 2022
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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 + Details
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