Details of Selected Balance Sheet Accounts - Accounts Receivable (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts receivable, gross	$ 242,232	$ 290,308
Allowance for doubtful accounts	(8,745)	(6,701)
Accounts receivable, net	233,487	283,607
Trade
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts receivable, gross	178,813	227,052
Unbilled revenue
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts receivable, gross	28,341	35,674
Contract assets
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts receivable, gross	26,034	21,201
Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts receivable, gross	$ 9,044	$ 6,381