Accounts Receivable - Schedule of Accounts Receivable (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross accounts receivable	$ 403,198	$ 374,741
Allowance for doubtful accounts	(2,055)	(829)
Reserve for cash-basis customers	(304)	(5,316)
Total accounts receivable reserves	(2,359)	(6,145)
Accounts receivable, net	400,839	368,596
Unbilled accounts receivable
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross accounts receivable	117,888	113,765
Trade accounts receivable
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross accounts receivable	$ 285,310	$ 260,976