Summary of Significant Accounting Policies - Narrative (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015 USD ($) ft² tenant store property	Sep. 30, 2014 USD ($)	Sep. 30, 2015 USD ($) ft² tenant store property shares	Sep. 30, 2014 USD ($)	Dec. 31, 2014 USD ($)
Significant Accounting Policies [Line Items]
Number of tenants | tenant	1		1
Number of shopping centers | store	31		31
Allowance for doubtful accounts receivables	$ 1,600		$ 1,600		$ 700
Period expected for the sale of property to occur			1 year
Area of real estate property (in sq ft) | ft²	197,127		197,127
Property held-for-sale, accumulated depreciation	$ 7,000		$ 7,000
Liabilities on property held-for-sale	400		400
Deferred debt costs	9,091		9,091		9,874
Accumulated amortization, deferred debt costs	6,600		6,600		5,900
Deferred leasing costs, net	26,891		26,891		26,928
Accumulated amortization deferred leasing cost	25,400		25,400		21,600
Amortization expense deferred leasing cost			4,200	$ 3,900
Interest capitalized	600	$ 186	$ 1,393	430
Commercial development projects, availability for occupancy, maximum period after major construction activity			1 year
Depreciation expense			$ 28,200	26,800
Repairs and maintenance expense			$ 9,000	$ 9,200
Shares credited to directors' deferred fee accounts | shares			239,558
Percentage of ownership in Operating Partnership			74.20%
Other Assets
Significant Accounting Policies [Line Items]
Property held-for-sale, book value	$ 3,300		$ 3,300
Held-for-sale
Significant Accounting Policies [Line Items]
Number of real estate properties | property	1		1
Minimum
Significant Accounting Policies [Line Items]
Accounts receivable, net representing rental income accrued	$ 40,600		$ 40,600		38,700
Allowance for doubtful accounts receivables representing rental income accrued	$ 500		$ 500		$ 300
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			4.50%
Number of shopping centers | store			9
Safeway
Significant Accounting Policies [Line Items]
Percentage of total revenue			2.50%
Number of shopping centers | store			8
Revenues
Significant Accounting Policies [Line Items]
Number of tenants | tenant	2		2
Percentage of total revenue			2.50%