Summary of Significant Accounting Policies - Revenues - Accounts Receivables (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2014 joint_venture	Dec. 31, 2013	Dec. 31, 2012
Accounts, Notes, Loans and Financing Receivable [Line Items]
Tenant Receivables	$ 10,583reg_TenantReceivables	$ 6,550reg_TenantReceivables
Document Fiscal Year Focus	2014
Current Fiscal Year End Date	--12-31
Number of Joint Ventures, Unilateral Dissolution Right	5
Provision for doubtful accounts	2,192us-gaap_ProvisionForDoubtfulAccounts	1,841us-gaap_ProvisionForDoubtfulAccounts	3,006us-gaap_ProvisionForDoubtfulAccounts
Accrued CAM, insurance and tax reimbursements receivables	15,369	16,280
Other receivables	9,570us-gaap_OtherReceivables	7,411us-gaap_OtherReceivables
Less: allowance for doubtful accounts	(4,523)	(3,922)
Accounts Receivable, Net	30,999us-gaap_AccountsReceivableNet	26,319us-gaap_AccountsReceivableNet
Percentage Of Revenue By Customer	5.00%us-gaap_ConcentrationRiskPercentage1
Maximum [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Percentage Of Revenue By Customer	5.00%
Discontinued operations
Accounts, Notes, Loans and Financing Receivable [Line Items]
Provision for doubtful accounts	$ 0	$ 53	$ 58

End date of current fiscal year in the format --MM-DD.

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This is focus fiscal year of the document report in CCYY format. For a 2006 annual report, which may also provide financial information from prior periods, fiscal 2006 should be given as the fiscal year focus. Example: 2006.

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Number Of Joint Ventures That Grant Each Partner A Right To Dissolve The Real Estate Partnership

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For an unclassified balance sheet, the amount due from customers or clients for goods or services that have been delivered or sold in the normal course of business, reduced to their estimated net realizable fair value by an allowance established by the entity of the amount it deems uncertain of collection.

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For an unclassified balance sheet, a valuation allowance for receivables due a company that are expected to be uncollectible.

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For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division.

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Carrying amounts due as of the balance sheet date from parties or arising from transactions not otherwise specified in the taxonomy.

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Amount of expense related to write-down of receivables to the amount expected to be collected. Includes, but is not limited to, accounts receivable and notes receivable.

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