Earnings Per Share (Details) (USD $) In Thousands, except Share data	3 Months Ended				9 Months Ended
	Sep. 30, 2011		Sep. 30, 2010		Sep. 30, 2011		Sep. 30, 2010
Numerator:
Income from continuing operations	$ 5,402		$ 8,501		$ 31,651		$ 59,757
Net (income) attributable to noncontrolling interests in the Operating Partnership from continuing operations	(225)		(352)		(1,323)		(2,761)
Net (income)/loss attributable to noncontrolling interests in consolidated affiliates from continuing operations	(249)		148		(554)		(281)
Dividends on Preferred Stock	(627)		(1,677)		(3,926)		(5,031)
Excess of Preferred Stock redemption/repurchase cost over carrying value	0		0		(1,895)		0
Income from continuing operations available for common stockholders	4,301		6,620		23,953		51,684
Income from discontinued operations	2,842		272		3,470		1,147
Net (income) attributable to noncontrolling interests in the Operating Partnership from discontinued operations	(141)		(14)		(173)		(58)
Income from discontinued operations available for common stockholders	2,701		258		3,297		1,089
Net income available for common stockholders	7,002		6,878		27,250		52,773
Denominator:
Denominator for basic earnings per Common Share - weighted average shares	72,492,000		71,631,000		72,176,000		71,549,000
Earnings per Common Share - basic:
Income from continuing operations available for common stockholders (in dollars per share)	$ 0.06		$ 0.10		$ 0.33		$ 0.72
Income from discontinued operations available for common stockholders (in dollars per share)	$ 0.04		$ 0.00		$ 0.05		$ 0.02
Net income available for common stockholders (in dollars per share)	$ 0.10		$ 0.10		$ 0.38		$ 0.74
Numerator:
Income from continuing operations	5,402		8,501		31,651		59,757
Net (income)/loss attributable to noncontrolling interests in consolidated affiliates from continuing operations	(249)		148		(554)		(281)
Dividends on Preferred Stock	(627)		(1,677)		(3,926)		(5,031)
Excess of Preferred Stock redemption/repurchase cost over carrying value	0		0		(1,895)		0
Income from continuing operations available for common stockholders before net (income) attributable to noncontrolling interests in the Operating Partnership	4,526		6,972		25,276		54,445
Income from discontinued operations available for common stockholders	2,842		272		3,470		1,147
Net income available for common stockholders before net (income) attributable to noncontrolling interests in the Operating Partnership	$ 7,368		$ 7,244		$ 28,746		$ 55,592
Denominator:
Denominator for basic earnings per Common Share -weighted average shares	72,492,000		71,631,000		72,176,000		71,549,000
Stock options using the treasury method	138,000		210,000		169,000		183,000
Noncontrolling interests partnership units	3,772,000		3,797,000		3,782,000		3,805,000
Denominator for diluted earnings per Common Share - adjusted weighted average shares and assumed conversions (1)	76,402,000	[1]	75,638,000	[1]	76,127,000	[1]	75,537,000	[1]
Earnings per Common Share - diluted:
Income from continuing operations available for common stockholders (in dollars per share)	$ 0.06		$ 0.10		$ 0.33		$ 0.72
Income from discontinued operations available for common stockholders (in dollars per share)	$ 0.04		$ 0.00		$ 0.05		$ 0.02
Net income available for common stockholders (in dollars per share)	$ 0.10		$ 0.10		$ 0.38		$ 0.74
Number of anti-dilutive options and warrants not included in earnings per share (in dollars per share)	400,000		700,000		300,000		700,000

[1] (1) There were 0.4 million and 0.7 million options outstanding during the three months ended September 30, 2011 and 2010, respectively, and 0.3 million and 0.7 million options outstanding during the nine months ended September 30, 2011 and 2010, respectively, that were not included in the computation of diluted earnings per share because the impact of including such options would be anti-dilutive.