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Segment Information (Narrative) (Details)
12 Months Ended
Dec. 31, 2018
Segment
Customer
Dec. 31, 2017
Customer
Dec. 31, 2016
Customer
Segment Reporting Information [Line Items]      
Number of reportable segments | Segment 3    
Revenue from Contract with Customer [Member] | Customer Concentration Risk [Member]      
Segment Reporting Information [Line Items]      
Concentration risk, customer | Customer 0 1 1
Concentration risk, percentage 10.00% 10.00% 10.00%