Earnings per Share and Unit Earnings per Share and Unit (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
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Weighted Average Limited Partnership Units Outstanding, Basic	177,164	189,164	177,164	298,330
Partnership Interest [Member]
Earnings Per Share [Abstract]
Income from continuing operations, including portion attributable to noncontrolling interest	$ 12,362	$ 13,399	$ 39,077	$ 37,494
(Loss) income from Discontinued Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest	2,179	474	2,531	7,523
Net income	14,541	13,873	41,608	45,017
Net income attributable to noncontrolling interest	154	95	425	271
Dividends paid on unvested restricted stock	187	158	560	474
Net income attributable to common stockholders	8,350	7,770	23,073	26,722
Add: dividends paid on treasury method restricted stock	(5)	0	(33)	0
Net income for common stockholders - diluted	8,355	7,770	23,106	26,722
Weighted Average Number of Shares Outstanding, Basic	89,683,000	81,356,000	87,422,000	81,316,000
Incremental shares to be issued under unvested restricted stock	11,000	0	24,000	0
Incremental common shares attributable to equity forward agreements	0	1,410,000	565,000	1,340,000
Weighted Average Number of Shares Outstanding, Diluted	89,694,000	82,766,000	88,011,000	82,656,000
Earnings Per Unit [Abstract]
Income from continuing operations, including portion attributable to noncontrolling interest	12,362	13,399	39,077	37,494
(Loss) income from discontinued operations	2,179	474	2,531	7,523
Net income	14,541	13,873	41,608	45,017
Preferred unit distributions	5,850	5,850	17,550	17,550
Net income attributable to noncontrolling interest	154	95	425	271
Net income attributable to common unit holders	8,537	7,928	23,633	27,196
Dividends paid on unvested restricted stock	187	158	560	474
Add: dividends paid on treasury method restricted stock	(5)	0	(33)	0
Incremental shares to be issued under unvested restricted stock	11,000	0	24,000	0
Incremental common shares attributable to equity forward agreements	0	1,410,000	565,000	1,340,000
Continuing operations	$ 0.07	$ 0.09	$ 0.23	$ 0.24
Discontinued operations	$ 0.02	$ 0.01	$ 0.03	$ 0.09
Net income attributable to common unit holders	$ 0.09	$ 0.10	$ 0.26	$ 0.33
Continuing operations	$ 0.07	$ 0.09	$ 0.23	$ 0.23
Discontinued operations	$ 0.02	$ 0.00	$ 0.03	$ 0.09
Net income attributable to common unit holders	$ 0.09	$ 0.09	$ 0.26	$ 0.32
Parent Company [Member]
Earnings Per Share [Abstract]
Income from continuing operations, including portion attributable to noncontrolling interest	12,362	13,399	39,077	37,494
(Loss) income from Discontinued Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest	2,179	474	2,531	7,523
Net income	14,541	13,873	41,608	45,017
Preferred Stock Dividends, Income Statement Impact	4,919	4,919	14,756	14,756
Net income attributable to noncontrolling interest	1,112	1,060	3,296	3,220
Net income attributable to common stockholders	8,510	7,894	23,556	27,041
Dividends paid on unvested restricted stock	187	158	560	474
Net income attributable to common stockholders	8,323	7,736	22,996	26,567
Add: dividends paid on treasury method restricted stock	(5)	0	(33)	0
Net income for common stockholders - diluted	8,328	7,736	23,029	26,567
Weighted Average Number of Shares Outstanding, Basic	89,506,000	81,167,000	87,245,000	81,017,000
Incremental shares to be issued under unvested restricted stock	11,000	0	24,000	0
Incremental common shares attributable to equity forward agreements	0	1,410,000	565,000	1,340,000
Weighted Average Number of Shares Outstanding, Diluted	89,517,000	82,577,000	87,834,000	82,357,000
Income (Loss) from Continuing Operations, Per Basic Share	$ 0.07	$ 0.09	$ 0.23	$ 0.24
Discontinued operations	$ 0.02	$ 0.01	$ 0.03	$ 0.09
Net income attributable to common stockholders	$ 0.09	$ 0.10	$ 0.26	$ 0.33
Continuing operations	$ 0.07	$ 0.09	$ 0.23	$ 0.23
Discontinued operations	$ 0.02	$ 0.00	$ 0.03	$ 0.09
Net income attributable to common stockholders	$ 0.09	$ 0.09	$ 0.26	$ 0.32
Earnings Per Unit [Abstract]
Income from continuing operations, including portion attributable to noncontrolling interest	12,362	13,399	39,077	37,494
(Loss) income from discontinued operations	2,179	474	2,531	7,523
Net income	14,541	13,873	41,608	45,017
Net income attributable to noncontrolling interest	1,112	1,060	3,296	3,220
Dividends paid on unvested restricted stock	187	158	560	474
Add: dividends paid on treasury method restricted stock	$ (5)	$ 0	$ (33)	$ 0
Incremental shares to be issued under unvested restricted stock	11,000	0	24,000	0
Incremental common shares attributable to equity forward agreements	0	1,410,000	565,000	1,340,000