Summary of Significant Accounting Policies (Narrative) (Details)	3 Months Ended								12 Months Ended
	Dec. 31, 2019 USD ($)	Sep. 30, 2019 USD ($)	Jun. 30, 2019 USD ($)	Mar. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Sep. 30, 2018 USD ($)	Jun. 30, 2018 USD ($)	Mar. 31, 2018 USD ($)	Dec. 31, 2019 USD ($) Segment	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($) shares	Dec. 31, 2015	May 01, 2019 shares	Apr. 30, 2019 shares	Jan. 01, 2019 USD ($)
Summary Of Significant Accounting Policies [Line Items]
VIE real estate owned carrying value	$ 1,515,206,000				$ 1,508,682,000				$ 1,515,206,000	$ 1,508,682,000	$ 1,534,599,000
Mortgage loan payable	46,370,000				47,315,000				46,370,000	47,315,000
Depreciation expense									41,800,000	36,100,000	36,500,000
Cash at consolidated joint ventures	300,000				200,000				300,000	200,000
Allowance for doubtful accounts receivable	5,600,000				5,900,000				5,600,000	5,900,000
Provision for doubtful accounts included in operating, maintenance and management expenses									$ 400,000	2,200,000	1,700,000
Number of reportable segment | Segment									1
Operating lease, right-of-use asset	13,638,000								$ 13,638,000						$ 14,600,000
Operating lease, right-of-use liability	13,778,000								13,778,000
Operating lease cost									2,800,000
Total revenues	35,628,000	$ 35,912,000	$ 35,660,000	$ 36,883,000	$ 36,932,000	$ 36,170,000	$ 41,350,000	$ 37,568,000	144,083,000	152,020,000	146,008,000
Adjustment to opening equity prior period									$ 500,000
Rents [Member] | Accounting Standards Update 2016-02 [Member]
Summary Of Significant Accounting Policies [Line Items]
Total revenues										113,900,000	113,300,000
Expense Recoveries [Member] | Accounting Standards Update 2016-02 [Member]
Summary Of Significant Accounting Policies [Line Items]
Total revenues										$ 33,400,000	$ 31,200,000
Accounts Payable and Accrued Liabilities [Member]
Summary Of Significant Accounting Policies [Line Items]
Operating lease, right-of-use liability															$ 14,600,000
2017 Stock Incentive Plan [Member]
Summary Of Significant Accounting Policies [Line Items]
Maximum number of shares may be issued under the plan | shares													6,000,000	2,000,000
Maximum number of shares to be granted per year to a participant | shares											500,000
Minimum [Member]
Summary Of Significant Accounting Policies [Line Items]
Real estate investments useful life									3 years
Maximum [Member]
Summary Of Significant Accounting Policies [Line Items]
Real estate investments useful life									40 years
New London Mall [Member] | New London Joint Venture [Member]
Summary Of Significant Accounting Policies [Line Items]
Acquired ownership percentage in joint venture												60.00%
Percentage of joint venture ownership												100.00%
Variable Interest Entity, Primary Beneficiary [Member] | Other Ownership Interest [Member]
Summary Of Significant Accounting Policies [Line Items]
VIE real estate owned carrying value	37,600,000								$ 37,600,000
Mortgage loan payable	0								$ 0
Variable Interest Entity, Primary Beneficiary [Member] | Crossroads II [Member] | Other Ownership Interest [Member]
Summary Of Significant Accounting Policies [Line Items]
Ownership percentage									60.00%
Variable Interest Entity, Primary Beneficiary [Member] | San Souci Plaza [Member]
Summary Of Significant Accounting Policies [Line Items]
VIE real estate owned carrying value	26,200,000								$ 26,200,000
Mortgage loan payable	$ 0								$ 0