Earnings Per Share (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2012		Mar. 31, 2011
Numerator:
Income from continuing operations	$ 13,115		$ 11,903
Net (income) attributable to noncontrolling interests in the Operating Partnership from continuing operations	(571)		(480)
Net (income) attributable to noncontrolling interests in consolidated affiliates from continuing operations	(184)		(123)
Dividends on Preferred Stock	(627)		(1,677)
Income from continuing operations available for common stockholders	11,733		9,623
Income from discontinued operations	5,217		540
Net (income) attributable to noncontrolling interests in the Operating Partnership from discontinued operations	(256)		(27)
Income from discontinued operations available for common stockholders	4,961		513
Net income available for common stockholders	16,694		10,136
Denominator:
Denominator for basic earnings per Common Share - weighted average shares (in shares)	72,836,000	[1],[2]	71,817,000	[1],[2]
Earnings per Common Share - basic:
Income from continuing operations available for common stockholders (in dollars per share)	$ 0.16		$ 0.13
Income from discontinued operations available for common stockholders (in dollars per share)	$ 0.07		$ 0.01
Net income available for common stockholders (in dollars per share)	$ 0.23		$ 0.14
Numerator:
Income from continuing operations	13,115		11,903
Net (income) attributable to noncontrolling interests in consolidated affiliates from continuing operations	(184)		(123)
Dividends on Preferred Stock	(627)		(1,677)
Income from continuing operations available for common stockholders before net (income) attributable to noncontrolling interests in the Operating Partnership	12,304		10,103
Income from discontinued operations	5,217		540
Net income available for common stockholders before net (income) attributable to noncontrolling interests in the Operating Partnership	$ 17,521		$ 10,643
Denominator:
Denominator for basic earnings per Common Share - weighted average shares (in shares)	72,836,000	[1],[2]	71,817,000	[1],[2]
Stock options using the treasury method	132,000		185,000
Noncontrolling interests Common Units	3,728,000		3,790,000
Denominator for diluted earnings per Common Share - adjusted weighted average shares and assumed conversions (in shares) (1)	76,696,000	[1]	75,792,000	[1]
Earnings per Common Share - diluted:
Income from continuing operations available for common stockholders (in dollars per share)	$ 0.16		$ 0.13
Income from discontinued operations available for common stockholders (in dollars per share)	$ 0.07		$ 0.01
Net income available for common stockholders (in dollars per share)	$ 0.23		$ 0.14
Number of anti-dilutive options and warrants not included in earnings per share (in dollars per share)	600,000		300,000

[1] There were 0.6 million and 0.3 million options outstanding during the three months ended March 31, 2012 and 2011, respectively, that were not included in the computation of diluted earnings per share because the impact of including such options would be anti-dilutive.

[2] Includes all unvested restricted stock since dividends on such restricted stock are non-forfeitable.