CONSOLIDATED STATEMENTS OF EQUITY (USD $) In Thousands, except Share data, unless otherwise specified	Total	Total Stockholders' Equity	Preferred Stock	Common Stock	Capital in Excess of Par Value	Cumulative Net Income	Accumulated OCI	Cumulative Distributions	Non-controlling Interests	Series E Preferred Stock	Series E Preferred Stock Total Stockholders' Equity	Series E Preferred Stock Preferred Stock	Series E Preferred Stock Common Stock	Series E Preferred Stock Capital in Excess of Par Value	Series E Preferred Stock Cumulative Distributions	Series F Preferred Stock	Series F Preferred Stock Total Stockholders' Equity	Series F Preferred Stock Preferred Stock	Series F Preferred Stock Capital in Excess of Par Value	Series F Preferred Stock Cumulative Distributions
Balance at Dec. 31, 2009	$ 454,313	$ 452,332	$ 186,801	$ 233	$ 326,163	$ 577,629	$ 390	$ (638,884)	$ 1,981
Balance (in shares) at Dec. 31, 2009			7,932,000	23,312,000
Increase (Decrease) in Stockholders' Equity
Conversion of 8.5% Series E Preferred Stock												(823)	1	822
Conversion of 8.5% Series E Preferred Stock (in shares)												(33,000)	66,000
Redemption of preferred stock, partial and full										(123)	(123)	(123)		6	(6)	(58,942)	(58,942)	(58,942)	2,377	(2,377)
Redemption of preferred stock, partial and full (in shares)												(5,000)						(2,358,000)
Reclassification adjustment	(126)	(126)					(126)
Stock option exercises	182	182			182
Stock option exercises (in shares)				12,000
Issue common stock	67,793	67,793		27	67,766
Issue common stock (in shares)				2,746,000
Issue restricted stock				2	(2)
Issue restricted stock (in shares)				209,000
Net income	46,053	45,862				45,862			191
Vested stock options	75	75			75
Vested restricted stock	1,210	1,210			1,210
Non-controlling interests preferred return	(210)								(210)
Preferred stock dividends	(13,662)	(13,662)						(13,662)
Common stock cash distributions ($1.79, $1.68 and $1.58 per share for the year ended 2012, 2011 and 2010, respectively)	(39,041)	(39,041)						(39,041)
Balance at Dec. 31, 2010	457,522	455,560	126,913	263	398,599	623,491	264	(693,970)	1,962
Balance (in shares) at Dec. 31, 2010			5,536,000	26,345,000
Increase (Decrease) in Stockholders' Equity
Redemption of preferred stock, partial and full																(88,413)	(88,413)	(88,413)	3,566	(3,566)
Redemption of preferred stock, partial and full (in shares)																(3,536,530)		(3,536,000)
Reclassification adjustment	(65)	(65)					(65)
Stock option exercises	120	120			120
Stock option exercises (in shares)				5,000
Issue common stock	103,631	103,631		40	103,591
Issue common stock (in shares)				3,990,000
Issue restricted stock (in shares)				6,000
Net income	49,443	49,252				49,252			191
Vested stock options	17	17			17
Vested restricted stock	1,450	1,450			1,450
Non-controlling interests preferred return	(191)								(191)
Preferred stock dividends	(5,512)	(5,512)						(5,512)
Common stock cash distributions ($1.79, $1.68 and $1.58 per share for the year ended 2012, 2011 and 2010, respectively)	(49,292)	(49,292)						(49,292)
Balance at Dec. 31, 2011	468,710	466,748	38,500	303	507,343	672,743	199	(752,340)	1,962
Balance (in shares) at Dec. 31, 2011			2,000,000	30,346,000
Increase (Decrease) in Stockholders' Equity
Reclassification adjustment	(47)	(47)					(47)
Stock option exercises	1,926	1,926		1	1,925
Stock option exercises (in shares)	85,000			85,000
Issue restricted stock				1	(1)
Issue restricted stock (in shares)				90,000
Net income	51,327	51,290				51,290			37
Vested stock options	10	10			10
Vested restricted stock	1,809	1,809			1,809
Non-controlling interests conversion	(2,764)	(850)			(850)				(1,914)
Non-controlling interests conversion (in shares)				23,000
Non-controlling interests preferred return	(78)								(78)
Preferred stock dividends	(3,273)	(3,273)						(3,273)
Common stock cash distributions ($1.79, $1.68 and $1.58 per share for the year ended 2012, 2011 and 2010, respectively)	(54,512)	(54,512)						(54,512)
Balance at Dec. 31, 2012	$ 463,108	$ 463,101	$ 38,500	$ 305	$ 510,236	$ 724,033	$ 152	$ (810,125)	$ 7
Balance (in shares) at Dec. 31, 2012			2,000,000	30,544,000