Notes Receivable and Allowance for Credit Losses - Past Due Balances Of Mezzanine And Other Notes Receivable (Details) - Mezzanine & Other Notes Receivable - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Notes Receivable and Allowance for Losses [Line Items]
Total Past Due	$ 0	$ 0
Current	140,022	133,014
Total Notes Receivable	140,022	133,014
Senior
Notes Receivable and Allowance for Losses [Line Items]
Total Past Due	0	0
Current	104,924	98,545
Total Notes Receivable	104,924	98,545
Subordinated
Notes Receivable and Allowance for Losses [Line Items]
Total Past Due	0	0
Current	32,643	32,153
Total Notes Receivable	32,643	32,153
Unsecured
Notes Receivable and Allowance for Losses [Line Items]
Total Past Due	0	0
Current	2,455	2,316
Total Notes Receivable	2,455	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	0	0
Financing Receivables, Equal to Greater than 90 Days Past Due | Senior
Notes Receivable and Allowance for Losses [Line Items]
Total Past Due	0	0
Financing Receivables, Equal to Greater than 90 Days Past Due | Subordinated
Notes Receivable and Allowance for Losses [Line Items]
Total Past Due	0	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