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Employee Benefit Plans and Other Postretirement Benefits - Schedule of Pension Plan Asset Investments and Target Allocations (Details) | Dec. 31, 2021 | Dec. 31, 2020
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Fixed Income Securities |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Percentage of Fair Value | 67.00% | 48.00%
Fixed Income Securities | Packaging Corporation of America |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage | 70.00% |
International Equity Securities |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Percentage of Fair Value | 18.00% | 29.00%
U.S. Equity Securities |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Percentage of Fair Value | 13.00% | 21.00%
Other Securities |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Percentage of Fair Value | 2.00% | 2.00%
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 | 29.00% |

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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 -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 55 -Paragraph 17 -URI http://asc.fasb.org/extlink&oid=123450688&loc=d3e4179-114921 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (d)(i) -URI http://asc.fasb.org/extlink&oid=123447040&loc=d3e1928-114920 + Details
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