Notes Receivable and Allowance for Credit Losses - Schedule Of Notes Receivable (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019	Dec. 31, 2018
Notes Receivable and Allowance for Losses [Line Items]
Notes receivable	$ 139,712	$ 133,014
Total allowance for notes receivable credit losses	16,295	4,556	$ 4,685
Total notes receivable, net of allowance	123,417	128,458
Current portion, net of allowance	25,608	25,404
Long-term portion, net of allowance	97,809	103,054
Senior
Notes Receivable and Allowance for Losses [Line Items]
Notes receivable	105,592	98,545
Subordinated
Notes Receivable and Allowance for Losses [Line Items]
Notes receivable	32,667	32,153
Unsecured
Notes Receivable and Allowance for Losses [Line Items]
Notes receivable	$ 1,453	$ 2,316