Summary of Significant Accounting Policies - Additional Information (Details) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2014 tenant store	Jun. 30, 2013	Jun. 30, 2014 tenant store	Jun. 30, 2013	Dec. 31, 2013
Significant Accounting Policies [Line Items]
Number of tenants	1		1
Number of shopping centers	31		31
Allowance for doubtful accounts receivables	$ 400,000		$ 400,000		$ 600,000
Period expected for the sale of property to occur			1 year
Deferred debt costs, net	10,564,000		10,564,000		9,675,000
Accumulated amortization deferred leasing cost	5,200,000		5,200,000		4,500,000
Deferred leasing costs, net	26,693,000		26,693,000		26,052,000
Accumulated amortization deferred leasing cost	19,100,000		19,100,000		16,600,000
Amortization expense deferred leasing cost			2,600,000	3,200,000
Severance payments			1,100,000
Interest expensed capitalized	140,000	34,000	243,000	34,000
Commercial development projects, availability for occupancy, maximum period after major construction activity			1 year
Depreciation and amortization expense			17,900,000	25,600,000
Increase (decrease) in depreciation expense			(7,700,000)
Repairs and maintenance expense			6,500,000	4,900,000
Property operating expenses	6,138,000	6,041,000	13,723,000	11,990,000
Shares credited to directors' deferred fee accounts			227,233
Percentage of ownership in Operating Partnership			74.30%
Snow removal costs
Significant Accounting Policies [Line Items]
Property operating expenses			1,700,000
Held-for-sale
Significant Accounting Policies [Line Items]
Number of real estate properties	0		0
Van Ness Square
Significant Accounting Policies [Line Items]
Additional depreciation expense as a result of reduction in estimated useful life			8,000,000
Estimated remaining useful life			4 months
Minimum
Significant Accounting Policies [Line Items]
Accounts receivable, net representing rental income accrued	37,500,000		37,500,000		37,200,000
Allowance for doubtful accounts receivables representing rental income accrued	$ 200,000		$ 200,000		$ 500,000
Minimum | Building
Significant Accounting Policies [Line Items]
Estimated useful life			35 years
Maximum | Building
Significant Accounting Policies [Line Items]
Estimated useful life			50 years
Maximum | Building Improvements
Significant Accounting Policies [Line Items]
Estimated useful life			20 years
Giant Food
Significant Accounting Policies [Line Items]
Percentage of total revenue			4.60%
Number of shopping centers			9
Safeway
Significant Accounting Policies [Line Items]
Percentage of total revenue			2.50%
Number of shopping centers			8
Revenues
Significant Accounting Policies [Line Items]
Number of tenants	2		2
Percentage of total revenue			2.50%