Significant Customers & Concentration of Credit Risk (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Concentration Risk [Line Items]
Unbilled accounts receivable	$ 100,494		$ 110,575
Single Customer
Concentration Risk [Line Items]
Unbilled accounts receivable	20,500
Single Financial Services Customer
Concentration Risk [Line Items]
Unbilled accounts receivable	$ 9,500
Revenue | Customer Concentration Risk | Single Customer
Concentration Risk [Line Items]
Concentration risk percentage	15.00%	13.00%
Revenue | Customer Concentration Risk | Single Financial Services Customer
Concentration Risk [Line Items]
Concentration risk percentage	9.00%	9.00%
Revenue | Customer Concentration Risk | Automotive Sector
Concentration Risk [Line Items]
Concentration risk percentage	25.00%	24.00%
Revenue | Customer Concentration Risk | Financial & Insurance Sector
Concentration Risk [Line Items]
Concentration risk percentage	17.00%	16.00%
Accounts Receivable | Customer Concentration Risk | Single Customer
Concentration Risk [Line Items]
Concentration risk percentage	20.00%
Accounts Receivable | Customer Concentration Risk | Single Financial Services Customer
Concentration Risk [Line Items]
Concentration risk percentage	7.00%