Other Retirement Plans (Narrative) (Details)	12 Months Ended
Dec. 31, 2019
Initial Critical Year
Multiemployer Plans [Line Items]
Multiemployer Plan, Collective-Bargaining Arrangement, Percentage of Contributions Required for Multiple Collective-Bargaining Arrangements	5.00%
Succeeding Plan Years
Multiemployer Plans [Line Items]
Multiemployer Plan, Collective-Bargaining Arrangement, Percentage of Contributions Required for Multiple Collective-Bargaining Arrangements	10.00%

Percentage of contributions required of employer under collective bargaining arrangement to total contributions required under all collective bargaining arrangements for pension and other postretirement plan to which two or more unrelated employers contribute where assets contributed by one participating employer may be used to provide benefits to employees of other participating employers.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-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_MultiemployerPlanCollectiveBargainingArrangementPercentageOfContributionsRequiredForMultipleCollectiveBargainingArrangements
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration