Significant Customers & Concentration of Credit Risk (Details Textual) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Concentration Risk [Line Items]
Unbilled accounts receivable		$ 127,649		$ 119,335
Single Customer
Concentration Risk [Line Items]
Unbilled accounts receivable		13,200
Single Financial Services Customer
Concentration Risk [Line Items]
Unbilled accounts receivable		$ 26,400
Revenue | Single Customer
Concentration Risk [Line Items]
Concentration risk percentage	13.00%	14.00%
Revenue | Single Financial Services Customer
Concentration Risk [Line Items]
Concentration risk percentage		14.00%	14.00%
Revenue | Automotive Industry
Concentration Risk [Line Items]
Concentration risk percentage		21.00%	22.00%
Revenue | Financial & Insurance Industry [Member]
Concentration Risk [Line Items]
Concentration risk percentage		20.00%	20.00%
Accounts Receivable | Single Customer
Concentration Risk [Line Items]
Concentration risk percentage		10.00%
Accounts Receivable | Single Financial Services Customer
Concentration Risk [Line Items]
Concentration risk percentage		16.00%