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	23,612,000	0	0	23,160,000	0	452,000
Net unrealized change in fair value of interest rate swap	743,000	0	0	0	743,000	0
Common dividends declared - $1.60 per share	(48,830,000)	0	0	(48,830,000)	0	0
Stock-based compensation, net of forfeitures	4,324,000	0	(4,324,000)	0	0	0
Issuance of 579,198 shares of common stock, common stock offering, net of expenses	33,490,000	0	33,490,000	0	0	0
Issuance of 4,500 shares of common stock, options exercised	120,000	0	120,000	0	0	0
Issuance of 2,703 shares of common stock, dividend reinvestment plan	156,000	0	156,000	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	(579,000)	0	0	0	0	(579,000)
BALANCE at Sep. 30, 2013	$ 503,684,000	$ 3,000	$ 769,512,000	$ (270,919,000)	$ 351,000	$ 4,737,000