Earnings per Share and Unit Earnings per Share and Unit (Details) (USD $) In Thousands, except Share data	3 Months Ended		6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Weighted Average Limited Partnership Units Outstanding, Basic	177,164	256,598	177,164	354,126
Partnership Interest [Member]
Earnings Per Share [Abstract]
Income from continuing operations, including portion attributable to noncontrolling interest	$ 18,937	$ 13,812	$ 27,067	$ 24,348
(Loss) income from Discontinued Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest	0	(108)	0	6,795
Net income	18,937	13,704	27,067	31,143
Net income attributable to noncontrolling interest	189	79	271	175
Dividends paid on unvested restricted stock	218	178	437	356
Net income attributable to common stockholders	12,680	7,597	14,659	18,912
Add: dividends paid on treasury method restricted stock	(20)	0	(34)	0
Net income for common stockholders - diluted	12,700	7,597	14,693	18,912
Weighted Average Number of Shares Outstanding, Basic	89,251	81,311	86,267	81,306
Incremental shares to be issued under unvested restricted stock	44	0	36	0
Incremental common shares attributable to equity forward agreements	0	1,522	848	1,305
Weighted Average Number of Shares Outstanding, Diluted	89,295	82,833	87,151	82,611
Earnings Per Unit [Abstract]
Income from continuing operations, including portion attributable to noncontrolling interest	18,937	13,812	27,067	24,348
(Loss) income from discontinued operations	0	(108)	0	6,795
Net income	18,937	13,704	27,067	31,143
Preferred unit distributions	5,850	5,850	11,700	11,700
Net income attributable to noncontrolling interest	189	79	271	175
Net income attributable to common unit holders	12,898	7,775	15,096	19,268
Dividends paid on unvested restricted stock	218	178	437	356
Add: dividends paid on treasury method restricted stock	(20)	0	(34)	0
Incremental shares to be issued under unvested restricted stock	44	0	36	0
Incremental common shares attributable to equity forward agreements	0	1,522	848	1,305
Continuing operations	$ 0.14	$ 0.09	$ 0.17	$ 0.15
Discontinued operations	$ 0.00	$ 0.00	$ 0.00	$ 0.08
Net income attributable to common unit holders	$ 0.14	$ 0.09	$ 0.17	$ 0.23
Continuing operations	$ 0.14	$ 0.09	$ 0.17	$ 0.15
Discontinued operations	$ 0.00	$ 0.00	$ 0.00	$ 0.08
Net income attributable to common unit holders	$ 0.14	$ 0.09	$ 0.17	$ 0.23
Parent Company [Member]
Earnings Per Share [Abstract]
Income from continuing operations, including portion attributable to noncontrolling interest	18,937	13,812	27,067	24,348
(Loss) income from Discontinued Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest	0	(108)	0	6,795
Net income	18,937	13,704	27,067	31,143
Preferred Stock Dividends, Income Statement Impact	4,919	4,919	9,838	9,838
Net income attributable to noncontrolling interest	1,157	1,037	2,183	2,158
Net income attributable to common stockholders	12,861	7,748	15,046	19,147
Dividends paid on unvested restricted stock	218	178	437	356
Net income attributable to common stockholders	12,643	7,570	14,609	18,791
Add: dividends paid on treasury method restricted stock	20	0	34	0
Net income for common stockholders - diluted	12,663	7,570	14,643	18,791
Weighted Average Number of Shares Outstanding, Basic	89,074	81,054	86,090	80,952
Incremental shares to be issued under unvested restricted stock	44	0	36	0
Incremental common shares attributable to equity forward agreements	0	1,522	848	1,305
Weighted Average Number of Shares Outstanding, Diluted	89,118	82,576	86,974	82,257
Income (Loss) from Continuing Operations, Per Basic Share	$ 0.14	$ 0.09	$ 0.17	$ 0.15
Discontinued operations	$ 0.00	$ 0.00	$ 0.00	$ 0.08
Net income attributable to common stockholders	$ 0.14	$ 0.09	$ 0.17	$ 0.23
Continuing operations	$ 0.14	$ 0.09	$ 0.17	$ 0.15
Discontinued operations	$ 0.00	$ 0.00	$ 0.00	$ 0.08
Net income attributable to common stockholders	$ 0.14	$ 0.09	$ 0.17	$ 0.23
Earnings Per Unit [Abstract]
Income from continuing operations, including portion attributable to noncontrolling interest	18,937	13,812	27,067	24,348
(Loss) income from discontinued operations	0	(108)	0	6,795
Net income	18,937	13,704	27,067	31,143
Net income attributable to noncontrolling interest	1,157	1,037	2,183	2,158
Dividends paid on unvested restricted stock	218	178	437	356
Add: dividends paid on treasury method restricted stock	$ 20	$ 0	$ 34	$ 0
Incremental shares to be issued under unvested restricted stock	44	0	36	0
Incremental common shares attributable to equity forward agreements	0	1,522	848	1,305