Commitments and Contingencies (Concentrations of Risk) (Narrative) (Details) - numberOfCustomers			3 Months Ended
	Mar. 31, 2021	Dec. 31, 2020	Mar. 31, 2021	Mar. 31, 2020
Concentration Risk [Line Items]
Number of customers			330
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	2	2
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	14.00%	15.00%
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	10.00%	12.00%
Revenue [Member] | Customer Concentration Risk [Member] | Ten Largest Customers [Member]
Concentration Risk [Line Items]
Number of customers			10	10
Concentration risk, percentage of total			68.00%	62.00%