Notes Receivable and Allowance for Credit Losses - Past Due Balances Of Mezzanine And Other Notes Receivable (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Notes Receivable and Allowance for Losses [Line Items]
Total Past Due	$ 17,409	$ 17,409
Current	123,146	121,908
Total Notes Receivable	140,555	139,317
Senior
Notes Receivable and Allowance for Losses [Line Items]
Total Past Due	15,200	15,200
Current	90,133	89,516
Total Notes Receivable	105,333	104,716
Subordinated
Notes Receivable and Allowance for Losses [Line Items]
Total Past Due	2,209	2,209
Current	31,463	31,025
Total Notes Receivable	33,672	33,234
Unsecured
Notes Receivable and Allowance for Losses [Line Items]
Total Past Due	0	0
Current	1,550	1,367
Total Notes Receivable	1,550	1,367
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	17,409	17,409
Financing Receivables, Equal to Greater than 90 Days Past Due | Senior
Notes Receivable and Allowance for Losses [Line Items]
Total Past Due	15,200	15,200
Financing Receivables, Equal to Greater than 90 Days Past Due | Subordinated
Notes Receivable and Allowance for Losses [Line Items]
Total Past Due	2,209	2,209
Financing Receivables, Equal to Greater than 90 Days Past Due | Unsecured
Notes Receivable and Allowance for Losses [Line Items]
Total Past Due	$ 0	$ 0