Commitments and Contingencies (Concentrations of Risk) (Narrative) (Details) - customer			3 Months Ended		6 Months Ended
	Jun. 30, 2018	Dec. 31, 2017	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Concentration Risk [Line Items]
Number of customers					395
Accounts Receivable, Net, Less BIEC [Member] | Credit Concentration Risk [Member] | Disclosed Customers with Highest Net Accounts Receivable Positions [Member]
Concentration Risk [Line Items]
Number of customers	3	2
Accounts Receivable, Net, Less BIEC [Member] | Credit Concentration Risk [Member] | Customer with Highest Net Accounts Receivable Position [Member]
Concentration Risk [Line Items]
Concentration risk, percentage of total	39.00%	46.00%
Accounts Receivable, Net, Less BIEC [Member] | Credit Concentration Risk [Member] | Customer with Second Highest Net Accounts Receivable Position [Member]
Concentration Risk [Line Items]
Concentration risk, percentage of total	18.00%	15.00%
Accounts Receivable, Net, Less BIEC [Member] | Credit Concentration Risk [Member] | Customer with Third Highest Net Accounts Receivable Position [Member]
Concentration Risk [Line Items]
Concentration risk, percentage of total	12.00%
Revenue [Member] | Customer Concentration Risk [Member] | Ten Largest Customers [Member]
Concentration Risk [Line Items]
Number of customers			10	10	10	10
Concentration risk, percentage of total			76.00%	84.00%	73.00%	79.00%