Earnings per Share and Unit (Details) (USD $) In Thousands, except Share data, unless otherwise specified	0 Months Ended	3 Months Ended		9 Months Ended
	Feb. 09, 2012	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 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		$ 19,784	$ 11,097	$ 48,770	$ 35,138
Discontinued operations		36	3,444	9,133	6,470
Net income		19,820	14,541	57,903	41,608
Less: Preferred stock dividends		7,932	4,919	27,265	14,756
Less: Noncontrolling interests		251	1,112	123	3,296
Net income attributable to common stockholders		11,637	8,510	30,515	23,556
Less: Dividends paid on unvested restricted stock		175	187	526	560
Net income attributable to common stock/unit holders - basic		11,462	8,323	29,989	22,996
Add: Dividends paid on Treasury Method restricted stock		31	5	61	33
Net income for common stock unit/holders - diluted		11,493	8,328	30,050	23,029
Weighted average common shares/units outstanding for basic EPS/EPU		89,594,000	89,506,000	89,491,000	87,245,000
Incremental shares to be issued under unvested restricted stock		68,000	11,000	44,000	24,000
Incremental shares under Forward Equity Offering		0	0	0	565,000
Weighted average common shares/units outstanding for diluted EPS/EPU		89,662,000	89,517,000	89,535,000	87,834,000
Income per common share/unit - basic:
Continuing operations (in dollars per share)		$ 0.13	$ 0.05	$ 0.24	$ 0.19
Discontinued operations (in dollars per share)		$ 0.00	$ 0.04	$ 0.10	$ 0.07
Net income attributable to common stockholders (in dollars per share)		$ 0.13	$ 0.09	$ 0.34	$ 0.26
Income per common share/unit - diluted:
Continuing operations (in dollars per share)		$ 0.13	$ 0.05	$ 0.24	$ 0.19
Discontinued operations (in dollars per share)		$ 0.00	$ 0.04	$ 0.10	$ 0.07
Net income attributable to common stockholders (in dollars per share)		$ 0.13	$ 0.09	$ 0.34	$ 0.26
Partnership Interest [Member]
Earnings Per Share [Abstract]
Income from continuing operations		19,784	11,097	48,770	35,138
Discontinued operations		36	3,444	9,133	6,470
Net income		19,820	14,541	57,903	41,608
Less: Preferred unit distributions	1,000	7,932	5,850	26,636	17,550
Less: Noncontrolling interests		212	154	636	425
Net income attributable to common unit holders		11,676	8,537	30,631	23,633
Less: Dividends paid on unvested restricted stock		175	187	526	560
Net income attributable to common stock/unit holders - basic		11,501	8,350	30,105	23,073
Add: Dividends paid on Treasury Method restricted stock		31	5	61	33
Net income for common stock unit/holders - diluted		$ 11,532	$ 8,355	$ 30,166	$ 23,106
Weighted average common shares/units outstanding for basic EPS/EPU		89,771,000	89,683,000	89,668,000	87,422,000
Incremental shares to be issued under unvested restricted stock		68,000	11,000	44,000	24,000
Incremental shares under Forward Equity Offering		0	0	0	565,000
Weighted average common shares/units outstanding for diluted EPS/EPU		89,839,000	89,694,000	89,712,000	88,011,000
Income per common unit - basic
Continuing operations (in dollars per share)		0.13	0.05	0.24	0.19
Discontinued operations (in dollars per share)		0.00	0.04	0.10	0.07
Net income attributable to common unit holders (in dollars per share)		0.13	0.09	0.34	0.26
Income per common unit - diluted
Continuing operations (in dollars per share)		0.13	0.05	0.24	0.19
Discontinued operations (in dollars per share)		0.00	0.04	0.10	0.07
Net Income (Loss), Per Outstanding Limited Partnership Unit, Diluted		0.13	0.09	0.34	0.26