Investment in and Advances to Affiliate - Schedule of Revenue From Contracts With Customers Included in Fee and Other Income on Consolidated Statements of Operations (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Disaggregation Of Revenue [Line Items]
Total revenue from contracts with customers	$ 14,398	$ 6,501	$ 30,983	$ 14,044
Retail Value Inc. [Member]
Disaggregation Of Revenue [Line Items]
Total revenue from contracts with customers	8,000		17,400
Asset and Property Management Fees [Member]
Disaggregation Of Revenue [Line Items]
Total revenue from contracts with customers	11,110	4,886	22,641	10,482
Asset and Property Management Fees [Member] | Retail Value Inc. [Member]
Disaggregation Of Revenue [Line Items]
Total revenue from contracts with customers	5,800		11,600
Leasing Commissions [Member]
Disaggregation Of Revenue [Line Items]
Total revenue from contracts with customers	1,381	1,312	2,880	2,934
Leasing Commissions [Member] | Retail Value Inc. [Member]
Disaggregation Of Revenue [Line Items]
Total revenue from contracts with customers	700		1,400
Disposition Fees [Member]
Disaggregation Of Revenue [Line Items]
Total revenue from contracts with customers	1,515	0	2,717	0
Disposition Fees [Member] | Retail Value Inc. [Member]
Disaggregation Of Revenue [Line Items]
Total revenue from contracts with customers	1,500		2,600
Credit Facility Guaranty and Refinancing Fees [Member]
Disaggregation Of Revenue [Line Items]
Total revenue from contracts with customers	0	$ 0	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	$ 0		$ 1,800