XML 121 R54.htm IDEA: XBRL DOCUMENT v3.19.3.a.u2
Summary of Significant Accounting Policies (Concentration of Credit Risk Narrative) (Details) - Customer Concentration Risk
12 Months Ended
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Sales Revenue | First Largest Customer      
Concentration Risk [Line Items]      
Concentration risk percentage 17.00% 18.00% 18.00%
Sales Revenue | Second Largest Customer      
Concentration Risk [Line Items]      
Concentration risk percentage 12.00% 12.00% 13.00%
Accounts Receivable | First Largest Customer      
Concentration Risk [Line Items]      
Concentration risk percentage 2.00% 11.00%  
Accounts Receivable | Second Largest Customer      
Concentration Risk [Line Items]      
Concentration risk percentage 4.00% 4.00%