Accounts Receivable - Schedule of Accounts Receivable (Details) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross accounts receivable	$ 401,926	$ 374,741
Allowance for doubtful accounts	(787)	(829)
Reserve for cash-basis customers	(347)	(5,316)
Total accounts receivable reserves	(1,134)	(6,145)
Accounts receivable, net	400,792	368,596
Unbilled accounts receivable
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross accounts receivable	123,463	113,765
Trade accounts receivable
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross accounts receivable	$ 278,463	$ 260,976