Investments 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
	Mar. 31, 2019	Mar. 31, 2018
Disaggregation Of Revenue [Line Items]
Total revenue from contracts with customers	$ 16,585	$ 7,543
Retail Value Inc. [Member]
Disaggregation Of Revenue [Line Items]
Total revenue from contracts with customers	9,500
Asset and Property Management Fees [Member]
Disaggregation Of Revenue [Line Items]
Total revenue from contracts with customers	11,531	5,596
Asset and Property Management Fees [Member] | Retail Value Inc. [Member]
Disaggregation Of Revenue [Line Items]
Total revenue from contracts with customers	5,800
Leasing Commissions [Member]
Disaggregation Of Revenue [Line Items]
Total revenue from contracts with customers	1,499	1,622
Leasing Commissions [Member] | Retail Value Inc. [Member]
Disaggregation Of Revenue [Line Items]
Total revenue from contracts with customers	800
Disposition Fees [Member]
Disaggregation Of Revenue [Line Items]
Total revenue from contracts with customers	1,202	0
Disposition Fees [Member] | Retail Value Inc. [Member]
Disaggregation Of Revenue [Line Items]
Total revenue from contracts with customers	1,100
Credit Facility Guaranty and Refinancing Fees [Member]
Disaggregation Of Revenue [Line Items]
Total revenue from contracts with customers	1,800	$ 0
Credit Facility Guaranty and Refinancing Fees [Member] | Retail Value Inc. [Member]
Disaggregation Of Revenue [Line Items]
Total revenue from contracts with customers	$ 1,800