Commitments and Contingencies (Concentrations of Risk) (Narrative) (Details) - numberOfCustomers			12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Concentration Risk [Line Items]
Number of customers			475
Accounts Receivable, Net, Less Contract Liabilities [Member] | Credit Concentration Risk [Member] | Customers with Largest Net Accounts Receivable Positions [Member]
Concentration Risk [Line Items]
Number of customers	2	3
Accounts Receivable, Net, Less Contract Liabilities [Member] | Credit Concentration Risk [Member] | Customer with Largest Net Accounts Receivable Position [Member]
Concentration Risk [Line Items]
Concentration risk, percentage of total	15.00%	17.00%
Accounts Receivable, Net, Less Contract Liabilities [Member] | Credit Concentration Risk [Member] | Customer with Second Largest Net Accounts Receivable Position [Member]
Concentration Risk [Line Items]
Concentration risk, percentage of total	12.00%	13.00%
Accounts Receivable, Net, Less Contract Liabilities [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%
Revenue Benchmark [Member] | Customer Concentration Risk [Member] | Ten Largest Customers [Member]
Concentration Risk [Line Items]
Number of customers			10	10	10
Concentration risk, percentage of total			58.00%	64.00%	72.00%