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Segments and Related Information (Narrative) (Details) - supplier
12 Months Ended
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Segment Reporting Information [Line Items]      
Disclosure on Geographic Areas, Description of Revenue from External Customers 0 0 0
Segment Reporting, Disclosure of Major Customers 0 0 0
number of major suppliers 2 2 2
Supplier Concentration Risk [Member]      
Segment Reporting Information [Line Items]      
Concentration Risk, Percentage 62.26% 58.80% 65.70%