CONSOLIDATED STATEMENTS OF CHANGES IN EQUITY - Unaudited (USD $)	Total	Common Stock	Additional Paid-in Capital	Distributions In Excess Of Earnings	Accumulated Other Comprehensive Income (Loss) [Member]	Noncontrolling Interest in Joint Ventures
BALANCE at Dec. 31, 2012	$ 491,176,000	$ 3,000	$ 731,950,000	$ (245,249,000)	$ (392,000)	$ 4,864,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	15,098,000	0	0	14,797,000	0	301,000
Net unrealized change in fair value of interest rate swap	2,340,000	0	0	0	2,340,000	0
Common dividends declared - $1.06 per share	(32,271,000)	0	0	(32,271,000)	0	0
Stock-based compensation, net of forfeitures	3,258,000	0	(3,258,000)	0	0	0
Issuance of 282,763 shares of common stock, common stock offering, net of expenses	15,857,000	0	15,857,000	0	0	0
Issuance of 4,500 shares of common stock, options exercised	120,000	0	120,000	0	0	0
Issuance of 1,843 shares of common stock, dividend reinvestment plan	105,000	0	105,000	0	0	0
Withheld 9,412 shares of common stock to satisfy tax withholding obligations in connection with the vesting of restricted stock	(528,000)	0	(528,000)	0	0	0
Distributions to noncontrolling interest	(390,000)	0	0	0	0	(390,000)
BALANCE at Jun. 30, 2013	$ 494,765,000	$ 3,000	$ 750,762,000	$ (262,723,000)	$ 1,948,000	$ 4,775,000