Commitments and Contingencies (Concentrations of Risk) (Narrative) (Details) - customer			12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Concentration Risk [Line Items]
Number of customers			475
Accounts Receivable, Net, Less Deferred Revenue [Member] | Credit Concentration Risk [Member] | Customers with Largest Net Accounts Receivable Positions [Member]
Concentration Risk [Line Items]
Number of customers	3	3
Accounts Receivable, Net, Less Deferred Revenue [Member] | Credit Concentration Risk [Member] | Customer with Largest Net Accounts Receivable Position [Member]
Concentration Risk [Line Items]
Concentration risk, percentage of total	17.00%	26.00%
Accounts Receivable, Net, Less Deferred Revenue [Member] | Credit Concentration Risk [Member] | Customer with Second Largest Net Accounts Receivable Position [Member]
Concentration Risk [Line Items]
Concentration risk, percentage of total	13.00%	18.00%
Accounts Receivable, Net, Less Deferred Revenue [Member] | Credit Concentration Risk [Member] | Customer With Third Largest Net Accounts Receivable Position [Member]
Concentration Risk [Line Items]
Concentration risk, percentage of total	11.00%	12.00%
Revenue [Member] | Customer Concentration Risk [Member] | Ten Largest Customers [Member]
Concentration Risk [Line Items]
Number of customers			10	10	10
Concentration risk, percentage of total			64.00%	72.00%	78.00%