Accounts Receivable - Schedule of Accounts Receivable (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross accounts receivable	$ 332,613	$ 275,691
Allowance for doubtful accounts	(1,032)	(708)
Reserve for cash-basis customers	(4,834)	(2,995)
Total accounts receivable reserves	(5,866)	(3,703)
Accounts receivable, net	326,747	271,988
Trade accounts receivable
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross accounts receivable	235,166	175,391
Unbilled accounts receivable
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross accounts receivable	$ 97,447	$ 100,300