Description of Business and Summary of Significant Accounting Policies - Accounts Receivable and the Allowance for Doubtful Accounts Receivable (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts receivable, after allowance for credit loss, current	$ 142,847	$ 153,565
Allowance for doubtful accounts	22,691	21,696
Provision for doubtful accounts	1,749	12,325	$ 3,571
Billed Revenues
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts receivable, after allowance for credit loss, current	97,600	118,300
Unbilled Revenues
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts receivable, after allowance for credit loss, current	$ 45,200	$ 35,300