Revenue - Receivables (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total customer receivables	$ 276,459	$ 298,118
Unbilled receivables	10,385	11,922
Billed receivables
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total customer receivables	$ 266,074	$ 286,196