Investment in Unconsolidated Entities - Narrative (Details)	6 Months Ended
	Jun. 30, 2020 USD ($) derivative_instrument	Jun. 30, 2019 USD ($)	Dec. 31, 2019 USD ($)
Variable Interest Entity [Line Items]
Investment in unconsolidated entities	$ 116,824,000		$ 118,861,000
Deferred gain on sale of property	$ 958,000
Equity investment basis adjustment, amortization period (in years)	30 years
Interest Rate Swap
Variable Interest Entity [Line Items]
Derivative liability	$ 378,000
Wholly-Owned Retail Properties
Variable Interest Entity [Line Items]
Purchase price	33,204,000	$ 142,642,000
Antoine Town Center | Wholly-Owned Retail Properties
Variable Interest Entity [Line Items]
Purchase price	22,254,000
IAGM Retail Fund I, LLC
Variable Interest Entity [Line Items]
Repayment of mortgage note payable on one retail property	14,872,000
Gain on sale	$ 1,741,000
IAGM Retail Fund I, LLC | Interest Rate Swap
Variable Interest Entity [Line Items]
Number of derivatives held | derivative_instrument	2
Derivative liability	$ 687,000
IAGM Retail Fund I, LLC | Interest Rate Swap | One-month LIBOR
Variable Interest Entity [Line Items]
Variable rate (percent)	1.55%
IAGM Retail Fund I, LLC | Interest Rate Swap, Effective Date April 1, 2020, 1.979% Fixed Interest
Variable Interest Entity [Line Items]
Notional amount	$ 45,000,000
Fixed interest rate	1.979%
IAGM Retail Fund I, LLC | Interest Rate Swap, Effective Date April 1, 2020, 1.956% Fixed Interest
Variable Interest Entity [Line Items]
Notional amount	$ 30,000,000
Fixed interest rate	1.956%
IAGM Retail Fund I, LLC
Variable Interest Entity [Line Items]
Ownership percentage	55.00%		55.00%