Other Retirement Plans (Narrative) (Details)	12 Months Ended
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%

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.

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

Name:	us-gaap_MultiemployerPlanPensionSignificantEmployerContributionUnderCollectiveBargainingArrangementToAllParticipatingEmployerContributionsPercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration