Mortgage Loans Payable And Unsecured Credit Facilities (Narrative) (Details) - USD ($)		12 Months Ended
	May 03, 2016	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Apr. 26, 2016	Feb. 05, 2015
Line Of Credit Facility [Line Items]
Unsecured revolving credit facility financing costs		$ 3,210,000
Payments of early extinguishment of debt costs		2,623,000	$ 105,000	$ 825,000
Mortgage loan payable		610,288,000
Other assets and deferred charges, net		29,506,000	29,196,000
Approximate amount of accumulated other comprehensive loss to be reclassified into earnings		3,000,000
Interest Rate Swap [Member]
Line Of Credit Facility [Line Items]
Interest rate swaps liability		2,300,000
Cash Flow Hedging, Count 3 [Member] | Interest Rate Swap [Member]
Line Of Credit Facility [Line Items]
Other assets and deferred charges, net		3,100,000
Secured Debt [Member]
Line Of Credit Facility [Line Items]
Mortgage loan payable		$ 28,661,000
Secured Debt [Member] | Franklin Village Plaza [Member]
Line Of Credit Facility [Line Items]
Secured mortgage loan payable refinanced	$ 40,300,000
Mortgage loan payable	$ 50,000,000
Mortgage interest rate	3.90%
Mortgage maturity date		Jun. 30, 2026
Unsecured credit facility [Member]
Line Of Credit Facility [Line Items]
Credit facility borrowing capacity						$ 310,000,000
Aggregate borrowing capacity including increase under accordion feature		$ 750,000,000
Term loan amount		150,000,000				100,000,000
Continuing Operations [Member]
Line Of Credit Facility [Line Items]
Unsecured revolving credit facility financing costs		3,210,000	3,202,000
Payments of early extinguishment of debt costs		2,600,000	100,000
Mortgage loan payable		610,288,000	$ 676,779,000
Mortgage Loans Payable [Member]
Line Of Credit Facility [Line Items]
Unsecured revolving credit facility financing costs		900,000
Term Loan [Member]
Line Of Credit Facility [Line Items]
Unsecured revolving credit facility financing costs		$ 2,300,000
Revolving Credit Facility [Member]
Line Of Credit Facility [Line Items]
Credit facility expiration date		Feb. 05, 2019
Extension period		1 year
Basis spread on borrowings variable rate		1.35%
Revolving Credit Facility [Member] | Minimum [Member]
Line Of Credit Facility [Line Items]
Basis spread on borrowings variable rate		1.35%
Revolving Credit Facility [Member] | Maximum [Member]
Line Of Credit Facility [Line Items]
Basis spread on borrowings variable rate		1.95%
Revolving Credit Facility [Member] | Unsecured credit facility [Member]
Line Of Credit Facility [Line Items]
Mortgage loan payable		$ 72,000,000
Credit facility borrowing capacity						260,000,000
Remaining borrowing capacity		$ 168,000,000
Term loan facility [Member]
Line Of Credit Facility [Line Items]
Basis spread on borrowings variable rate		1.30%
Term loan facility [Member] | Minimum [Member]
Line Of Credit Facility [Line Items]
Basis spread on borrowings variable rate		1.30%
Term loan facility [Member] | Maximum [Member]
Line Of Credit Facility [Line Items]
Basis spread on borrowings variable rate		1.90%
Term loan facility [Member] | Unsecured credit facility [Member]
Line Of Credit Facility [Line Items]
Credit facility borrowing capacity						50,000,000
Credit facility expiration date		Feb. 05, 2020
Term Loan Maturing February 11, 2019 [Member] | Unsecured credit facility [Member]
Line Of Credit Facility [Line Items]
Mortgage maturity date		Feb. 11, 2019
Basis spread on borrowings variable rate		1.30%
Term loan amount		$ 75,000,000
Debt term		5 years
Weighted-average interest rate		2.90%
Term Loan Maturing February 11, 2019 [Member] | Unsecured credit facility [Member] | Minimum [Member]
Line Of Credit Facility [Line Items]
Basis spread on borrowings variable rate		1.30%
Term Loan Maturing February 11, 2019 [Member] | Unsecured credit facility [Member] | Maximum [Member]
Line Of Credit Facility [Line Items]
Basis spread on borrowings variable rate		1.90%
Term Loan Maturing February 11, 2021 [Member] | Unsecured credit facility [Member]
Line Of Credit Facility [Line Items]
Mortgage maturity date		Feb. 11, 2021
Basis spread on borrowings variable rate		1.70%
Term loan amount		$ 75,000,000
Debt term		7 years
Weighted-average interest rate		4.00%
Term Loan Maturing February 11, 2021 [Member] | Unsecured credit facility [Member] | Minimum [Member]
Line Of Credit Facility [Line Items]
Basis spread on borrowings variable rate		1.70%
Term Loan Maturing February 11, 2021 [Member] | Unsecured credit facility [Member] | Maximum [Member]
Line Of Credit Facility [Line Items]
Basis spread on borrowings variable rate		2.30%
Term Loan Maturing February 5, 2020 [Member] | Unsecured credit facility [Member]
Line Of Credit Facility [Line Items]
Mortgage maturity date		Feb. 05, 2020
Basis spread on borrowings variable rate		1.30%
Term loan amount						$ 50,000,000
Debt term		5 years
Weighted-average interest rate		2.80%
Term Loan Maturing February 5, 2020 [Member] | Unsecured credit facility [Member] | Minimum [Member]
Line Of Credit Facility [Line Items]
Basis spread on borrowings variable rate		1.30%
Term Loan Maturing February 5, 2020 [Member] | Unsecured credit facility [Member] | Maximum [Member]
Line Of Credit Facility [Line Items]
Basis spread on borrowings variable rate		1.90%
Term Loan Maturing February 5, 2022 [Member] | Unsecured credit facility [Member]
Line Of Credit Facility [Line Items]
Mortgage maturity date		Feb. 05, 2022
Basis spread on borrowings variable rate		1.55%
Term loan amount		$ 50,000,000
Debt term		7 years
Weighted-average interest rate		3.30%
Term Loan Maturing February 5, 2022 [Member] | Unsecured credit facility [Member] | Minimum [Member]
Line Of Credit Facility [Line Items]
Basis spread on borrowings variable rate		1.55%
Term Loan Maturing February 5, 2022 [Member] | Unsecured credit facility [Member] | Maximum [Member]
Line Of Credit Facility [Line Items]
Basis spread on borrowings variable rate		2.15%
Term Loan Maturing April 26, 2023 [Member] | Unsecured credit facility [Member]
Line Of Credit Facility [Line Items]
Mortgage maturity date		Apr. 26, 2023
Basis spread on borrowings variable rate		1.65%
Term loan amount					$ 100,000,000
Weighted-average interest rate		3.20%
Term Loan Maturing April 26, 2023 [Member] | Unsecured credit facility [Member] | Minimum [Member]
Line Of Credit Facility [Line Items]
Basis spread on borrowings variable rate		1.65%
Term Loan Maturing April 26, 2023 [Member] | Unsecured credit facility [Member] | Maximum [Member]
Line Of Credit Facility [Line Items]
Basis spread on borrowings variable rate		2.25%