Commitments and Contingencies (Concentrations of Risk) (Narrative) (Details) - customer			3 Months Ended
	Mar. 31, 2017	Dec. 31, 2016	Mar. 31, 2017	Mar. 31, 2016
Concentration Risk [Line Items]
Number of customers			305
Accounts Receivable, Net, Less Billings in Excess of Costs and Earnings [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	19.00%	17.00%
Accounts Receivable, Net, Less Billings in Excess of Costs and Earnings [Member] | Credit Concentration Risk [Member] | Customer with Second Highest Net Accounts Receivable Position [Member]
Concentration Risk [Line Items]
Concentration risk, percentage of total	16.00%	24.00%
Revenue [Member] | Customer Concentration Risk [Member] | Ten Largest Customers [Member]
Concentration Risk [Line Items]
Number of customers			10	10
Concentration risk, percentage of total			76.00%	73.00%