Notes Receivable and Allowance for Losses - Past due balances (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Financing Receivable, Credit Quality Indicator [Line Items]
Total Past Due	$ 17,409	$ 0
Current	121,908	133,014
Total Notes Receivable	139,317	133,014
Senior
Financing Receivable, Credit Quality Indicator [Line Items]
Total Past Due	15,200	0
Current	89,516	98,545
Total Notes Receivable	104,716	98,545
Subordinated
Financing Receivable, Credit Quality Indicator [Line Items]
Total Past Due	2,209	0
Current	31,025	32,153
Total Notes Receivable	33,234	32,153
Unsecured
Financing Receivable, Credit Quality Indicator [Line Items]
Total Past Due	0	0
Current	1,367	2,316
Total Notes Receivable	1,367	2,316
Financing Receivables, 30 to 89 Days Past Due
Financing Receivable, Credit Quality Indicator [Line Items]
Total Past Due	0	0
Financing Receivables, 30 to 89 Days Past Due | Senior
Financing Receivable, Credit Quality Indicator [Line Items]
Total Past Due	0	0
Financing Receivables, 30 to 89 Days Past Due | Subordinated
Financing Receivable, Credit Quality Indicator [Line Items]
Total Past Due	0	0
Financing Receivables, 30 to 89 Days Past Due | Unsecured
Financing Receivable, Credit Quality Indicator [Line Items]
Total Past Due	0	0
Financing Receivables, Equal to Greater than 90 Days Past Due
Financing Receivable, Credit Quality Indicator [Line Items]
Total Past Due	17,409	0
Financing Receivables, Equal to Greater than 90 Days Past Due | Senior
Financing Receivable, Credit Quality Indicator [Line Items]
Total Past Due	15,200	0
Financing Receivables, Equal to Greater than 90 Days Past Due | Subordinated
Financing Receivable, Credit Quality Indicator [Line Items]
Total Past Due	2,209	0
Financing Receivables, Equal to Greater than 90 Days Past Due | Unsecured
Financing Receivable, Credit Quality Indicator [Line Items]
Total Past Due	$ 0	$ 0