Consolidated Statements of Operations (USD $) In Thousands, except Per Share data	3 Months Ended		6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010
Parent Company [Member]
Revenues
Minimum rent	$ 89,684	$ 85,845	$ 179,068	$ 172,049
Percentage rent	151	264	1,058	624
Recoveries from tenants and other income	26,352	25,624	55,317	56,207
Management, transaction, and other fees	12,195	9,518	20,053	16,449
Total revenues	128,382	121,251	255,496	245,329
Operating Expenses
Depreciation and amortization	32,057	31,395	67,247	62,623
Operating and maintenance	17,861	17,221	37,436	34,819
General and administrative	15,177	12,656	32,131	27,974
Real estate taxes	14,297	14,378	29,000	28,871
Provision for doubtful accounts	1,586	63	2,212	2,402
Other expenses (income)	735	1,080	(174)	1,687
Total operating expenses	81,713	76,793	167,852	158,376
Other expense (income):
Interest expense, net of interest income of $587 and $640 for the three months ended June 30, 2011 and 2010, respectively, and $1,188 and $1,315 for the six months ended June 30, 2011 and 2010, respectively	30,563	30,635	61,428	59,764
Loss (gain) on sale of properties in development	0	226	0	(565)
(Income) loss from deferred compensation plan	(143)	988	(888)	374
Loss on derivatve instruments	0	(579)	0	(922)
Total other expense (income)	(30,420)	(32,428)	(60,540)	(60,495)
Income before equity in income (loss) of investments in real estate partnerships	16,249	12,030	27,104	26,458
Equity in income (loss) of investments in real estate partnerships	2,688	1,782	(37)	(2,110)
Income from continuing operations	18,937	13,812	27,067	24,348
Discontinued operations, net:
Operating (loss) income	0	(76)	0	30
(Loss) gain on sale of operating properties and properties in development	0	(32)	0	6,765
(Loss) income from discontinued operations	0	(108)	0	6,795
Net income	18,937	13,704	27,067	31,143
Noncontrolling interests:
Preferred units	(931)	(931)	(1,862)	(1,862)
Exchangeable operating partnership units	(37)	(27)	(50)	(121)
Limited partners' interest in consolidated partnerships	(189)	(79)	(271)	(175)
Net income attributable to noncontrolling interests	(1,157)	(1,037)	(2,183)	(2,158)
Net income attributable to controlling interests	17,780	12,667	24,884	28,985
Preferred stock dividends	(4,919)	(4,919)	(9,838)	(9,838)
Net income attributable to common stockholders	12,861	7,748	15,046	19,147
Income per common share/unit - basic:
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
Income per common share/unit - diluted:
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
Partnership Interest [Member]
Revenues
Minimum rent	89,684	85,845	179,068	172,049
Percentage rent	151	264	1,058	624
Recoveries from tenants and other income	26,352	25,624	55,317	56,207
Management, transaction, and other fees	12,195	9,518	20,053	16,449
Total revenues	128,382	121,251	255,496	245,329
Operating Expenses
Depreciation and amortization	32,057	31,395	67,247	62,623
Operating and maintenance	17,861	17,221	37,436	34,819
General and administrative	15,177	12,656	32,131	27,974
Real estate taxes	14,297	14,378	29,000	28,871
Provision for doubtful accounts	1,586	63	2,212	2,402
Other expenses (income)	735	1,080	(174)	1,687
Total operating expenses	81,713	76,793	167,852	158,376
Other expense (income):
Interest expense, net of interest income of $587 and $640 for the three months ended June 30, 2011 and 2010, respectively, and $1,188 and $1,315 for the six months ended June 30, 2011 and 2010, respectively	30,563	30,635	61,428	59,764
Loss (gain) on sale of properties in development	0	226	0	(565)
(Income) loss from deferred compensation plan	(143)	988	(888)	374
Loss on derivatve instruments	0	(579)	0	(922)
Total other expense (income)	(30,420)	(32,428)	(60,540)	(60,495)
Income before equity in income (loss) of investments in real estate partnerships	16,249	12,030	27,104	26,458
Equity in income (loss) of investments in real estate partnerships	2,688	1,782	(37)	(2,110)
Income from continuing operations	18,937	13,812	27,067	24,348
Discontinued operations, net:
Operating (loss) income	0	(76)	0	30
(Loss) gain on sale of operating properties and properties in development	0	(32)	0	6,765
(Loss) income from discontinued operations	0	(108)	0	6,795
Net income	18,937	13,704	27,067	31,143
Noncontrolling interests:
Limited partners' interest in consolidated partnerships	(189)	(79)	(271)	(175)
Net income attributable to noncontrolling interests	(189)	(79)	(271)	(175)
Net income attributable to controlling interests	18,748	13,625	26,796	30,968
Preferred unit distributions	(5,850)	(5,850)	(11,700)	(11,700)
Net income attributable to common unit holders	$ 12,898	$ 7,775	$ 15,096	$ 19,268
Income per common share/unit - basic:
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
Income per common share/unit - diluted:
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