Commitments and Contingencies (Concentrations of Risk) (Narrative) (Details) - customer			12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Concentration Risk [Line Items]
Number of customers			500
Accounts Receivable, Net, Less BIEC [Member] | Credit Concentration Risk [Member] | Customer with Highest Net Accounts Receivable Position [Member]
Concentration Risk [Line Items]
Number of customers	1	1
Concentration risk, percentage of total	46.00%	24.00%
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	15.00%	17.00%
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			78.00%	76.00%	61.00%