Notes Receivable and Allowance for Losses - Narrative (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Notes Receivable and Allowance for Losses [Line Items]
Loan reserves	$ 4,685		$ 4,685
Mezzanine & Other Notes Receivable
Notes Receivable and Allowance for Losses [Line Items]
Impaired financing receivable, unpaid principal balance	51,800		51,800
Mezzanine & Other Notes Receivable | Impaired Loans
Notes Receivable and Allowance for Losses [Line Items]
Impaired receivables, recorded investment	52,100		52,100
Impaired receivables, related allowance	4,400		4,400
Average notes receivable, nonaccrual status	1,700	$ 1,800
Interest income, impaired loans	1,500	$ 43
Mezzanine & Other Notes Receivable | Non-impaired Loans
Notes Receivable and Allowance for Losses [Line Items]
Loan reserves	300		300
Variable Interest Entity, Not Primary Beneficiary | Mezzanine & Other Notes Receivable
Notes Receivable and Allowance for Losses [Line Items]
Loans and financing receivable	115,000		114,300
Interest Rate Below Market Reduction | Variable Interest Entity, Not Primary Beneficiary | Mezzanine & Other Notes Receivable
Notes Receivable and Allowance for Losses [Line Items]
Loans and financing receivable	13,800		12,900
Receivable with Imputed Interest, discount	$ 1,300		$ 1,500