Debt - Additional Information (Detail)				1 Months Ended	3 Months Ended		6 Months Ended
	Dec. 27, 2017 USD ($)	May 24, 2017 USD ($)	Feb. 23, 2017 USD ($)	Nov. 30, 2016 USD ($)	Jun. 30, 2018 USD ($) Asset	Jun. 30, 2017	Jun. 30, 2018 USD ($) Asset	Jun. 30, 2017	Dec. 31, 2017 USD ($)	Jul. 07, 2015 USD ($)
Debt Instrument [Line Items]
Principal amount outstanding					$ 144,111,000		$ 144,111,000		$ 143,210,000
Amount transferred to redevelopment project reserve				$ 30,000,000
Amount to be transferred to redevelopment project reserve on monthly basis				$ 3,300,000
Principal terms of amendments							Company (i) posted $30.0 million, and will post $3.3 million on a monthly basis, to a redevelopment project reserve account, which amounts may be used by the Company to fund redevelopment activity and (ii) extended the spread maintenance provision for prepayment of the loan by two months through March 9, 2018 (with the spread maintenance premium for the second month at a reduced amount). As a result of this agreement and the resolution of the related disagreement, no cash flow sweep was imposed.
Minimum net worth					1,000,000,000		$ 1,000,000,000
Minimum liquidity					$ 50,000,000		$ 50,000,000
Debt instrument, base annual interest rate					6.50%		6.50%
Debt instrument, base interest rate period one							1.50%
Debt instrument, base interest rate period two							3.50%
Debt instrument, interest rate terms							The principal amount of loans outstanding under the Unsecured Delayed Draw Term Loan bore a base annual interest rate of 6.50%. If a cash flow sweep period were to have occurred and been continuing under the Company’s Mortgage Loan Agreement (i) the interest rate on any outstanding advances would have increased from and after such date by 1.5% per annum above the base interest rate and (ii) the interest rate on any advances made after such date would have increased by 3.5% per annum above the base interest rate.
Five Assets [Member]
Debt Instrument [Line Items]
Percentage of interest sold					49.90%		49.90%
Number of other assets disposed | Asset					5		5
UTC and West Hartford [Member] | Five Assets [Member]
Debt Instrument [Line Items]
Percentage of interest sold					50.00%		50.00%
Mortgage Loans and Future Funding Facility [Member]
Debt Instrument [Line Items]
Principal amount outstanding					$ 1,079,000,000		$ 1,079,000,000
Mortgage Loans [Member]
Debt Instrument [Line Items]
Reduction of amounts outstanding under mortgage loan							$ (131,400,000)
Mortgage loan agreement, description							The Loan Agreements contain customary covenants for a real estate financing, including restrictions that limit the Company’s ability to grant liens on its assets, incur additional indebtedness, or transfer or sell assets, as well as those that may require the Company to obtain lender approval for certain major tenant leases or significant redevelopment projects. Such restrictions also include cash flow sweep provisions based upon certain measures of the Company’s and Sears Holdings’ financial and operating performance, including (a) where the “Debt Yield” (the ratio of net operating income for the mortgage borrowers to their debt) is less than 11.0%, (b) if the performance of Sears Holdings at the stores subject to the Master Lease with Sears Holdings fails to meet specified rent ratio thresholds, (c) if the Company fails to meet specified tenant diversification tests and (d) upon the occurrence of a bankruptcy or insolvency action with respect to Sears Holdings or if there is a payment default under the Master Lease with Sears Holdings, in each case, subject to cure rights, including providing specified amounts of cash collateral or satisfying tenant diversification thresholds.
Maximum debt yield percentage							11.00%
Unamortized balance of company's debt issuance costs					$ 5,400,000		$ 5,400,000		8,500,000
Mortgage Loans [Member] | Future Funding Facility [Member]
Debt Instrument [Line Items]
Debt issuance and other costs							22,300,000
Unsecured Delayed Draw Term Loan [Member]
Debt Instrument [Line Items]
Line of credit facility, maximum			$ 200,000,000
Line of credit, maturity date			Dec. 31, 2017
Maximum net worth required for loan documentation							1,000,000,000
Amount outstanding at termination							$ 85,000,000
Unsecured Delayed Draw Term Loan [Member] | Maximum [Member]
Debt Instrument [Line Items]
Maximum leverage ratio							60.00%
Unsecured Delayed Draw Term Loan [Member] | Operating Partnership [Member]
Debt Instrument [Line Items]
Principal amount outstanding			$ 200,000,000
Upfront commitment fee			$ 1,000,000
Additional and final commitment fee paid		$ 1,000,000
Default interest rate on overdue amounts excess of base interest rate					1.50%		1.50%
Unsecured Term Loan [Member]
Debt Instrument [Line Items]
Principal amount outstanding					$ 200,000,000		$ 200,000,000
Unamortized balance of company's debt issuance costs	$ 1,800,000				900,000		900,000		$ 1,500,000
Line of credit facility, maximum					$ 200,000,000		$ 200,000,000
Line of credit, maturity date							Dec. 31, 2018
Debt instrument, base annual interest rate					6.75%		6.75%
Debt instrument, interest rate terms							The principal amount of loans outstanding under the Unsecured Term Loan bears a base annual interest rate of 6.75%.
Maximum net worth required for loan documentation							$ 1,000,000,000
Line of credit facility, current funding					$ 85,000,000		85,000,000
Additional Incremental loans							55,000,000
Line of credit facility, fee percentage	1.00%
Unsecured Term Loan [Member] | Empyrean Capital Partners, L.P. [Member]
Debt Instrument [Line Items]
Line of credit facility, maximum					145,000,000		145,000,000
Line of credit facility, current funding					$ 60,000,000		$ 60,000,000
Unsecured Term Loan [Member] | Maximum [Member]
Debt Instrument [Line Items]
Maximum leverage ratio							60.00%
Unsecured Term Loan [Member] | Operating Partnership [Member]
Debt Instrument [Line Items]
Line of credit facility, maximum	$ 200,000,000
Default interest rate on overdue amounts excess of base interest rate					1.50%		1.50%
Mortgage Loans over $1,000,000 [Member] | Mortgage Loans [Member]
Debt Instrument [Line Items]
Expiration date							Jul. 31, 2019
Interest rate description							Borrowings under the Mortgage Loans bear interest at the London Interbank Offered Rates (“LIBOR”) plus, as of June 30, 2018, a weighted-average spread of 485 basis points; payments are made monthly on an interest-only basis.
Basis spread on variable rate							4.85%
Frequency of interest payment							Monthly
Mortgage Loans over $1,000,000 [Member] | Mortgage Loans [Member] | Term Loans [Member]
Debt Instrument [Line Items]
Loan, face amount										$ 1,161,000,000
Mortgage Loans over $1,000,000 [Member] | Mortgage Loans [Member] | Future Funding Facility [Member]
Debt Instrument [Line Items]
Loan, face amount										$ 100,000,000
Weighted average interest rates					6.46%	5.86%	6.44%	5.77%