Revenues and Accounts Receivable - Schedule of Accounts Receivable, Net (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019	Dec. 31, 2018
Revenues And Accounts Receivable [Abstract]
Accounts receivable, invoiced	$ 52,372	$ 46,643
Accounts receivable, other	929	611
Allowance for doubtful accounts	(8,516)	(1,327)	$ (453)
Accounts receivable—net	$ 44,785	$ 45,927