Notes Receivable (Details) - USD ($)	Jun. 30, 2018	Nov. 10, 2016	Sep. 30, 2016
Mezzanine Loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Maximum loan commitment	$ 115,172,000
1405 Point
Accounts, Notes, Loans and Financing Receivable [Line Items]
Purchase option		88.00%
1405 Point | Mezzanine Loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Maximum loan commitment	28,232,000
1405 Point | Financial Guarantee
Accounts, Notes, Loans and Financing Receivable [Line Items]
Guarantor obligations, maximum exposure (up to)		$ 25,000,000.0
1405 Point | Financial Guarantee | Letter of Credit
Accounts, Notes, Loans and Financing Receivable [Line Items]
Credit facility, amount outstanding	2,100,000
The Residences at Annapolis Junction | Mezzanine Loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Maximum loan commitment	$ 48,105,000
The Residences at Annapolis Junction | Financial Guarantee
Accounts, Notes, Loans and Financing Receivable [Line Items]
Guarantor obligations, maximum exposure (up to)			$ 25,000,000
The Residences at Annapolis Junction | AJAO
Accounts, Notes, Loans and Financing Receivable [Line Items]
Purchase option			88.00%
Construction Loans | 1405 Point | Beatty Development Group
Accounts, Notes, Loans and Financing Receivable [Line Items]
Maximum borrowing capacity		$ 67,000,000
Construction Loans | The Residences at Annapolis Junction | AJAO
Accounts, Notes, Loans and Financing Receivable [Line Items]
Maximum borrowing capacity			$ 60,000,000