Description of Business and Summary of Significant Accounting Policies (Accounts Receivables and Allowances) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016
Accounts, Notes, Loans and Financing Receivable [Line Items]
Document Period End Date	Mar. 31, 2017
Accounts receivable	$ 68,424		$ 62,713
Allowance for doubtful accounts	2,962		$ 2,833
Deferred revenue included in accounts receivables	6,800
Provision for doubtful accounts	407	$ (241)
Allowance for Doubtful Accounts Receivable, Write-offs	82
Billed Revenues [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts receivable	57,000
Unbilled Revenues [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts receivable	$ 11,400
Maximum [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Delivery term for contractual elements of revenue arrangements	18 months