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Other Retirement Plans (Narrative) (Details) | 12 Months Ended
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Dec. 31, 2020
Initial Critical Year |
Multiemployer Plans [Line Items] |
Employer contribution under collective-bargaining arrangement to all participating employer contributions, percentage | 5.00%
Succeeding Plan Years |
Multiemployer Plans [Line Items] |
Employer contribution under collective-bargaining arrangement to all participating employer contributions, percentage | 10.00%

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- Definition Percentage of employer contribution required by collective-bargaining arrangement (CBA) to total contribution from all participating employers in multiemployer pension plan determined to be individually significant. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 80 -Section 50 -Paragraph 5 -Subparagraph (d) -URI http://asc.fasb.org/extlink&oid=65877416&loc=SL14450657-114947 + Details
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Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
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Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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- Details
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Data Type: | na
Balance Type: |
Period Type: |

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- Details
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Data Type: | na
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