Accounts Receivable - Schedule of Accounts Receivable (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross accounts receivable	$ 397,254	$ 374,741
Allowance for doubtful accounts	(994)	(829)
Reserve for cash-basis customers	(395)	(5,316)
Total accounts receivable reserves	(1,389)	(6,145)
Accounts receivable, net	395,865	368,596
Unbilled accounts receivable
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross accounts receivable	114,882	113,765
Trade accounts receivable
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross accounts receivable	$ 282,372	$ 260,976