Notes Receivable and Allowance for Credit Losses - Past Due Balances Of Mezzanine And Other Notes Receivable (Details) - Mezzanine & Other Notes Receivable - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Notes Receivable and Allowance for Losses [Line Items]
Total Past Due	$ 17,641	$ 0
Current	122,071	133,014
Total Notes Receivable	139,712	133,014
Senior
Notes Receivable and Allowance for Losses [Line Items]
Total Past Due	15,432	0
Current	90,160	98,545
Total Notes Receivable	105,592	98,545
Subordinated
Notes Receivable and Allowance for Losses [Line Items]
Total Past Due	2,209	0
Current	30,458	32,153
Total Notes Receivable	32,667	32,153
Unsecured
Notes Receivable and Allowance for Losses [Line Items]
Total Past Due	0	0
Current	1,453	2,316
Total Notes Receivable	1,453	2,316
Financing Receivables, 30 to 89 Days Past Due
Notes Receivable and Allowance for Losses [Line Items]
Total Past Due	0	0
Financing Receivables, 30 to 89 Days Past Due | Senior
Notes Receivable and Allowance for Losses [Line Items]
Total Past Due	0	0
Financing Receivables, 30 to 89 Days Past Due | Subordinated
Notes Receivable and Allowance for Losses [Line Items]
Total Past Due	0	0
Financing Receivables, 30 to 89 Days Past Due | Unsecured
Notes Receivable and Allowance for Losses [Line Items]
Total Past Due	0	0
Financing Receivables, Equal to Greater than 90 Days Past Due
Notes Receivable and Allowance for Losses [Line Items]
Total Past Due	17,641	0
Financing Receivables, Equal to Greater than 90 Days Past Due | Senior
Notes Receivable and Allowance for Losses [Line Items]
Total Past Due	15,432	0
Financing Receivables, Equal to Greater than 90 Days Past Due | Subordinated
Notes Receivable and Allowance for Losses [Line Items]
Total Past Due	2,209	0
Financing Receivables, Equal to Greater than 90 Days Past Due | Unsecured
Notes Receivable and Allowance for Losses [Line Items]
Total Past Due	$ 0	$ 0