Accounts Receivable - Schedule of Accounts Receivable (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross accounts receivable	$ 661,874	$ 553,823
Allowance for current expected credit losses and other reserves	(1,822)	(1,880)	$ (1,534)	$ (1,281)
Accounts receivable, net	660,052	551,943
Trade accounts receivable
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross accounts receivable	473,474	396,204
Unbilled accounts receivable
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross accounts receivable	$ 188,400	$ 157,619