Consolidated Statements of Stockholders' Equity (Parenthetical) (USD $)	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Pursuant to dividend reinvestment plan, shares	197,638	475,162	595,388
Exercise of employee stock options and issuance of directors' deferred stock, shares	172,887	56,002	158,219
Issuance of partnership units pursuant to dividend reinvestment plan, shares	196,183	88,309
Series A Preferred Stock
Redemption of preferred stock, shares	16,000	24,000
Series B Preferred Stock
Redemption of preferred stock, shares		31,731
Series C Preferred Stock
Issuance of common stock, shares	16,000	56,000
Dividend Declared
Distributions payable common stock (in usd per share)	0.40	0.36	0.36
Distributions partnership units (in usd per share)	0.40	0.36	0.36
Dividend Declared \| Series A Preferred Stock
Preferred stock (in usd per share)		50.00	50.00
Dividend Declared \| Series B Preferred Stock
Preferred stock (in usd per share)			56.25
Dividend Declared \| Series C Preferred Stock
Preferred stock (in usd per share)	42.97	42.97

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Aggregate dividends declared during the period for each share of common stock outstanding.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 505

-SubTopic 10

-Section S99

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-Number Topic 4

-Section F

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Number of new stock issued during the period.

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Number of shares (or other type of equity) issued during the period as a result of any equity-based compensation plan other than an employee stock ownership plan (ESOP), net of any shares forfeited. Shares issued could result from the issuance of restricted stock, the exercise of stock options, stock issued under employee stock purchase plans, and/or other employee benefit plans.

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