Description of Business and Summary of Significant Accounting Policies (Accounts Receivables and Allowances) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts receivable	$ 148,317		$ 148,317		$ 117,838
Allowance for doubtful accounts	6,069		6,069		$ 4,143
Deferred revenue included in accounts receivables	5,800		5,800
Provision for doubtful accounts	1,053	$ 316	2,098	$ 723
Allowance for Doubtful Accounts Receivable, Write-offs			137	$ 313
Billed Revenues [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts receivable	107,000		107,000
Unbilled Revenues [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts receivable	$ 41,300		$ 41,300