Earnings per Share and Unit (Details) (USD $) In Thousands, except Share data, unless otherwise specified	0 Months Ended	3 Months Ended		6 Months Ended
	Feb. 09, 2012	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Income per common unit - diluted
Weighted Average Limited Partnership Units Outstanding, Basic				177,164	177,164
Parent Company [Member]
Earnings Per Share [Abstract]
Income from continuing operations		$ 8,938	$ 17,316	$ 28,986	$ 24,042
Discontinued operations		2,410	1,621	9,097	3,025
Net income		11,348	18,937	38,083	27,067
Less: Preferred stock dividends		5,396	4,919	19,333	9,838
Less: Noncontrolling interests		255	1,157	(128)	2,183
Net income attributable to common stockholders		5,697	12,861	18,878	15,046
Less: Dividends paid on unvested restricted stock		206	218	411	437
Net income attributable to common stock/unit holders - basic		5,491	12,643	18,467	14,609
Add: Dividends paid on Treasury Method restricted stock		23	20	35	34
Net income for common stock unit/holders - diluted		5,514	12,663	18,502	14,643
Weighted average common shares/units outstanding for basic EPS/EPU		89,489,000	89,074,000	89,462,000	86,090,000
Incremental shares to be issued under unvested restricted stock		51,000	44,000	37,000	36,000
Incremental shares under Forward Equity Offering		0	0	0	848,000
Weighted average common shares/units outstanding for diluted EPS/EPU		89,540,000	89,118,000	89,499,000	86,974,000
Income per common share/unit - basic:
Continuing operations (in dollars per share)		$ 0.03	$ 0.12	$ 0.11	$ 0.13
Discontinued operations (in dollars per share)		$ 0.03	$ 0.02	$ 0.10	$ 0.04
Net income attributable to common stockholders (in dollars per share)		$ 0.06	$ 0.14	$ 0.21	$ 0.17
Income per common share/unit - diluted:
Continuing operations (in dollars per share)		$ 0.03	$ 0.12	$ 0.11	$ 0.13
Discontinued operations (in dollars per share)		$ 0.03	$ 0.02	$ 0.10	$ 0.04
Net income attributable to common stockholders (in dollars per share)		$ 0.06	$ 0.14	$ 0.21	$ 0.17
Partnership Interest [Member]
Earnings Per Share [Abstract]
Income from continuing operations		8,938	17,316	28,986	24,042
Discontinued operations		2,410	1,621	9,097	3,025
Net income		11,348	18,937	38,083	27,067
Less: Preferred unit distributions	1,000	5,396	5,850	18,704	11,700
Less: Noncontrolling interests		232	189	424	271
Net income attributable to common unit holders		5,720	12,898	18,955	15,096
Less: Dividends paid on unvested restricted stock		206	218	411	437
Net income attributable to common stock/unit holders - basic		5,514	12,680	18,544	14,659
Add: Dividends paid on Treasury Method restricted stock		23	20	35	34
Net income for common stock unit/holders - diluted		$ 5,537	$ 12,700	$ 18,579	$ 14,693
Weighted average common shares/units outstanding for basic EPS/EPU		89,666,000	89,251,000	89,639,000	86,267,000
Incremental shares to be issued under unvested restricted stock		51,000	44,000	37,000	36,000
Incremental shares under Forward Equity Offering		0	0	0	848,000
Weighted average common shares/units outstanding for diluted EPS/EPU		89,717,000	89,295,000	89,676,000	87,151,000
Income per common unit - basic
Continuing operations (in dollars per share)		0.03	0.12	0.11	0.13
Discontinued operations (in dollars per share)		0.03	0.02	0.10	0.04
Net income attributable to common unit holders (in dollars per share)		0.06	0.14	0.21	0.17
Income per common unit - diluted
Continuing operations (in dollars per share)		0.03	0.12	0.11	0.13
Discontinued operations (in dollars per share)		0.03	0.02	0.10	0.04
Net Income (Loss), Per Outstanding Limited Partnership Unit, Diluted		0.06	0.14	0.21	0.17