Accounts Receivable - Summary of Accounts Receivables (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Accounts Notes and Loans Receivable [Line Items]
Gross accounts receivable	$ 94,877			$ 105,127
Unearned income	(3,970)			(5,623)
Allowance for doubtful accounts	(15,141)	$ (14,277)	$ (10,889)	(10,494)	$ (4,408)
Net accounts receivable	75,766			89,010
Current trade receivables	57,920			58,977
Current unearned interest income	(2,675)			(3,942)
Long-term receivables	21,816			35,656
Long-term unearned interest income	(1,295)			(1,681)
Trade Accounts Receivable
Accounts Notes and Loans Receivable [Line Items]
Current trade receivables	57,920			58,977
Long-term receivables	$ 21,816			$ 35,656