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Asset Retirement Obligations - Changes to Asset Retirement Obligation (Parenthetical) (Details) $ in Millions | 12 Months Ended
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Dec. 31, 2020 USD ($)
Asset Retirement Obligation [Abstract] |
Revisions in estimated cash flows adjustment | $ 4.5

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- Definition Asset retirement obligation revision of estimate adjustment. + References No definition available. + Details
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Namespace Prefix: | pkg_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

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- References No definition available. + Details
Name: | us-gaap_AssetRetirementObligationAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration