Notes Receivable - Aging (Details) - USD ($)	9 Months Ended
	Sep. 30, 2021	Dec. 31, 2020	Dec. 31, 2019
Financing Receivable, Past Due [Line Items]
Notes receivable, gross	$ 135,147,310	$ 95,398,668
Financing Receivable, Allowance for Credit Loss	(16,905,196)	(11,133,146)	$ (3,461,837)
Notes receivable, net of allowance	$ 118,242,114	84,265,522
Weighted average days outstanding of notes receivable	34 days
Current
Financing Receivable, Past Due [Line Items]
Notes receivable, gross	$ 112,384,616	79,673,073
Financing Receivable, Allowance for Credit Loss	(4,032,714)	(2,692,254)
Notes receivable, net of allowance	108,351,902	76,980,819
1–28
Financing Receivable, Past Due [Line Items]
Notes receivable, gross	11,088,499	9,574,902
Financing Receivable, Allowance for Credit Loss	(3,712,417)	(3,616,327)
Notes receivable, net of allowance	7,376,082	5,958,575
29–56
Financing Receivable, Past Due [Line Items]
Notes receivable, gross	5,851,547	3,576,255
Financing Receivable, Allowance for Credit Loss	(4,051,641)	(2,646,627)
Notes receivable, net of allowance	1,799,906	929,628
57–90
Financing Receivable, Past Due [Line Items]
Notes receivable, gross	5,822,648	2,574,438
Financing Receivable, Allowance for Credit Loss	(5,108,424)	(2,177,938)
Notes receivable, net of allowance	$ 714,224	$ 396,500