CONSOLIDATED STATEMENTS OF CHANGES IN EQUITY (USD $) In Thousands, unless otherwise specified	Total	Common Stock	Additional Paid-in Capital	Distributions In Excess Of Earnings	Accumulated Other Comprehensive Loss	Noncontrolling Interest in Joint Ventures
BALANCE at Dec. 31, 2009	$ 447,096	$ 3	$ 589,197	$ (144,363)	$ (318)	$ 2,577
Comprehensive income
Net income	18,755	0	0	18,325	0	430
Net unrealized change in fair value of interest rate swap	318	0	0	0	318	0
Common dividends declared - $2.08, $2.08 and $2.10 per share in 2010, 2011 and 2012, respectively	(56,215)	0	0	(56,215)	0	0
Stock-based compensation, net of forfeitures	2,042	0	2,042	0	0	0
Issuance of 18,000, 9,250 and 4,500 shares of common stock, options exercised in 2010, 2011 and 2012, respectively	404	0	404	0	0	0
Issuance of 6,705, 5,989 and 3,915 shares of common stock, dividend reinvestment plan in 2010, 2011 and 2012, respectively	257	0	257	0	0	0
Withheld 19,668, 3,564 and 36,195 shares of common stock to satisfy tax withholding obligations in connection with the vesting of restricted stock in 2010, 2011 and 2012, respectively	(794)	0	(794)	0	0	0
Distributions to noncontrolling interest	(357)	0	0	0	0	(357)
BALANCE at Dec. 31, 2010	411,506	3	591,106	(182,253)	0	2,650
Comprehensive income
Net income	22,834	0	0	22,359	0	475
Net unrealized change in fair value of interest rate swap	0
Common dividends declared - $2.08, $2.08 and $2.10 per share in 2010, 2011 and 2012, respectively	(56,666)	0	0	(56,666)	0	0
Stock-based compensation, net of forfeitures	2,787	0	2,787	0	0	0
Issuance of 586,977 and 2,179,153 shares of common stock, common stock offering, net of expenses in 2011 and 2012, respectively	25,181	0	25,181	0	0	0
Issuance of 18,000, 9,250 and 4,500 shares of common stock, options exercised in 2010, 2011 and 2012, respectively	217	0	217	0	0	0
Issuance of 6,705, 5,989 and 3,915 shares of common stock, dividend reinvestment plan in 2010, 2011 and 2012, respectively	252	0	252	0	0	0
Withheld 19,668, 3,564 and 36,195 shares of common stock to satisfy tax withholding obligations in connection with the vesting of restricted stock in 2010, 2011 and 2012, respectively	(157)	0	(157)	0	0	0
Distributions to noncontrolling interest	(345)	0	0	0	0	(345)
BALANCE at Dec. 31, 2011	405,609	3	619,386	(216,560)	0	2,780
Comprehensive income
Net income	32,887	0	0	32,384	0	503
Net unrealized change in fair value of interest rate swap	(392)	0	0	0	(392)	0
Common dividends declared - $2.08, $2.08 and $2.10 per share in 2010, 2011 and 2012, respectively	(61,073)	0	0	(61,073)	0	0
Stock-based compensation, net of forfeitures	4,447	0	4,447	0	0	0
Issuance of 586,977 and 2,179,153 shares of common stock, common stock offering, net of expenses in 2011 and 2012, respectively	109,588	0	109,588	0	0	0
Issuance of 18,000, 9,250 and 4,500 shares of common stock, options exercised in 2010, 2011 and 2012, respectively	108	0	108	0	0	0
Issuance of 6,705, 5,989 and 3,915 shares of common stock, dividend reinvestment plan in 2010, 2011 and 2012, respectively	205	0	205	0	0	0
Withheld 19,668, 3,564 and 36,195 shares of common stock to satisfy tax withholding obligations in connection with the vesting of restricted stock in 2010, 2011 and 2012, respectively	(1,784)	0	(1,784)	0	0	0
Distributions to noncontrolling interest	(537)	0	0	0	0	(537)
Contributions from noncontrolling interest	2,118	0	0	0	0	2,118
BALANCE at Dec. 31, 2012	$ 491,176	$ 3	$ 731,950	$ (245,249)	$ (392)	$ 4,864