Earnings per Share and Unit (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Income per common unit - diluted
Weighted Average Limited Partnership Units Outstanding, Basic	167,649	177,164	173,946	177,164
Parent Company [Member]
Earnings Per Share [Abstract]
Income (Loss) from Continuing Operations, Including Portion Attributable to Noncontrolling Interest	$ 23,890	$ 17,781	$ 65,837	$ 45,907
Gain on sale of real estate	56	228	1,773	2,041
Income (Loss) from Continuing Operations Attributable to Noncontrolling Interest	367	248	992	103
Less: Noncontrolling interests	400	251	1,055	123
Income (Loss) from Continuing Operations Attributable to Parent	23,579	17,761	66,618	47,845
Preferred stock dividends	(5,266)	(7,932)	(15,797)	(27,265)
Less: Dividends paid on unvested restricted stock	148	175	445	526
Net income attributable to common stockholders	34,850	11,462	81,971	29,989
Add: Dividends paid on Treasury Method restricted stock	15	32	55	61
Net income for common stock unit/holders - diluted	34,865	11,494	82,026	30,050
Discontinued operations	16,718	1,811	31,658	9,955
Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Noncontrolling Interest	33	3	63	20
Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Parent	16,685	1,808	31,595	9,935
Weighted average common shares/units outstanding for basic EPS/EPU	91,985,000	89,594,000	91,147,000	89,491,000
Incremental shares to be issued under unvested restricted stock	33,000	68,000	40,000	44,000
Weighted average common shares/units outstanding for diluted EPS/EPU	92,018,000	89,662,000	91,187,000	89,535,000
Income per common share/unit - basic:
Continuing operations (in dollars per share)	$ 0.20	$ 0.11	$ 0.55	$ 0.23
Discontinued operations (in dollars per share)	$ 0.18	$ 0.02	$ 0.35	$ 0.11
Net income attributable to common stockholders (in dollars per share)	$ 0.38	$ 0.13	$ 0.90	$ 0.34
Income per common share/unit - diluted:
Continuing operations (in dollars per share)	$ 0.20	$ 0.11	$ 0.55	$ 0.23
Discontinued operations (in dollars per share)	$ 0.18	$ 0.02	$ 0.35	$ 0.11
Net income attributable to common stockholders (in dollars per share)	$ 0.38	$ 0.13	$ 0.90	$ 0.34
Partnership Interest [Member]
Earnings Per Share [Abstract]
Income (Loss) from Continuing Operations, Including Portion Attributable to Noncontrolling Interest	23,890	17,781	65,837	45,907
Gain on sale of real estate	56	228	1,773	2,041
Less: Noncontrolling interests	327	212	872	636
Income (Loss) from Continuing Operations Attributable to Parent	23,652	17,801	66,801	47,332
Less: Dividends paid on unvested restricted stock	148	175	445	526
Net income attributable to common stockholders	34,923	11,501	82,154	30,105
Add: Dividends paid on Treasury Method restricted stock	(15)	(31)	(55)	(61)
Net income for common stock unit/holders - diluted	34,938	11,532	82,209	30,166
Discontinued operations	16,718	1,811	31,658	9,955
Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Noncontrolling Interest	33	4	63	20
Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Parent	16,685	1,807	31,595	9,935
Preferred unit distributions	5,266	7,932	15,797	26,636
Weighted average common shares/units outstanding for basic EPS/EPU	92,153,000	89,771,000	91,321,000	89,668,000
Incremental shares to be issued under unvested restricted stock	33,000	68,000	40,000	44,000
Weighted average common shares/units outstanding for diluted EPS/EPU	92,186,000	89,839,000	91,361,000	89,712,000
Income per common unit - basic
Continuing operations (in dollars per share)	$ 0.20	$ 0.11	$ 0.55	$ 0.23
Discontinued operations (in dollars per share)	$ 0.18	$ 0.02	$ 0.35	$ 0.11
Net income attributable to common unit holders (in dollars per share)	$ 0.38	$ 0.13	$ 0.90	$ 0.34
Income per common unit - diluted
Continuing operations (in dollars per share)	$ 0.20	$ 0.11	$ 0.55	$ 0.23
Discontinued operations (in dollars per share)	$ 0.18	$ 0.02	$ 0.35	$ 0.11
Net income attributable to common unit holders (in dollars per share)	$ 0.38	$ 0.13	$ 0.90	$ 0.34
Continuing Operations [Member] | Parent Company [Member]
Earnings Per Share [Abstract]
Net income attributable to common stockholders	18,165	9,654	50,376	20,054
Net income for common stock unit/holders - diluted	18,180	9,686	50,431	20,115
Continuing Operations [Member] | Partnership Interest [Member]
Earnings Per Share [Abstract]
Income (Loss) from Continuing Operations Attributable to Noncontrolling Interest	294	208	809	616
Net income attributable to common stockholders	18,238	9,694	50,559	20,170
Net income for common stock unit/holders - diluted	$ 18,253	$ 9,725	$ 50,614	$ 20,231