Investment in and Advances to Affiliate - Schedule of Revenue From Contracts With Customers Included in Fee and Other Income on Consolidated Statement of Operations (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Disaggregation Of Revenue [Line Items]
Total revenue from contracts with RVI	$ 9,100	$ 11,945	$ 32,466	$ 42,928
Retail Value Inc. [Member]
Disaggregation Of Revenue [Line Items]
Total revenue from contracts with RVI	5,600	6,100	18,800	23,500
Asset and Property Management Fees [Member]
Disaggregation Of Revenue [Line Items]
Total revenue from contracts with RVI	7,326	9,751	24,201	32,392
Asset and Property Management Fees [Member] | Retail Value Inc. [Member]
Disaggregation Of Revenue [Line Items]
Total revenue from contracts with RVI	4,400	5,100	14,100	16,600
Leasing Commissions [Member]
Disaggregation Of Revenue [Line Items]
Total revenue from contracts with RVI	648	1,036	4,327	3,916
Leasing Commissions [Member] | Retail Value Inc. [Member]
Disaggregation Of Revenue [Line Items]
Total revenue from contracts with RVI	300	400	2,000	1,800
Disposition Fees [Member]
Disaggregation Of Revenue [Line Items]
Total revenue from contracts with RVI	856	546	2,622	3,263
Disposition Fees [Member] | Retail Value Inc. [Member]
Disaggregation Of Revenue [Line Items]
Total revenue from contracts with RVI	800	500	2,600	3,200
Credit Facility Guaranty and Refinancing Fees [Member]
Disaggregation Of Revenue [Line Items]
Total revenue from contracts with RVI	60	60	60	1,860
Credit Facility Guaranty and Refinancing Fees [Member] | Retail Value Inc. [Member]
Disaggregation Of Revenue [Line Items]
Total revenue from contracts with RVI	$ 100	$ 100	$ 100	$ 1,900