CONSOLIDATED STATEMENTS OF CHANGES IN EQUITY - Unaudited (USD $)	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, 2014	$ 575,615,000	$ 3,000	$ 874,335,000	$ (300,852,000)	$ (2,357,000)	$ 4,486,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	10,061,000	0	0	9,930,000	0	131,000
Net unrealized change in fair value of interest rate swaps	(2,535,000)	0	0	0	(2,535,000)	0
Common dividends declared - $.57 per share	(18,570,000)	0	0	(18,570,000)	0	0
Stock-based compensation, net of forfeitures	2,343,000	0	2,343,000	0	0	0
Issuance of 1,688 shares of common stock, common stock offering, net of expenses	52,000	0	52,000	0	0	0
Issuance of 1,044 shares of common stock, dividend reinvestment plan	63,000	0	63,000	0	0	0
Withheld 32,409 shares of common stock to satisfy tax withholding obligations in connection with the vesting of restricted stock	(2,041,000)	0	(2,041,000)	0	0	0
Distributions to noncontrolling interest	(181,000)	0	0	0	0	(181,000)
BALANCE at Mar. 31, 2015	$ 564,807,000	$ 3,000	$ 874,752,000	$ (309,492,000)	$ (4,892,000)	$ 4,436,000