Accounts Receivable - Schedule of Accounts Receivable (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross accounts receivable	$ 332,003	$ 275,691
Allowance for doubtful accounts	(774)	(708)
Reserve for cash-basis customers	(5,844)	(2,995)
Total accounts receivable reserves	(6,618)	(3,703)
Accounts receivable, net	325,385	271,988
Trade accounts receivable
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross accounts receivable	239,581	175,391
Unbilled accounts receivable
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross accounts receivable	$ 92,422	$ 100,300