Consolidated Statements of Operations (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Other expense (income):
Provision for Impairment	$ 15,900	$ 23,900	$ 103,900
Equity in income (loss) of investments in real estate partnerships	9,643	(12,884)	(26,373)
Parent Company [Member]
Revenues
Minimum rent	356,097	338,639	337,516
Percentage rent	2,996	2,540	3,585
Recoveries from tenants and other income	107,344	105,582	99,171
Management, transaction, and other fees	33,980	29,400	38,289
Total revenues	500,417	476,161	478,561
Operating Expenses
Depreciation and amortization	132,129	120,450	114,058
Operating and maintenance	72,626	68,496	64,030
General and administrative	56,117	61,502	53,177
Real estate taxes	55,542	53,462	52,375
Provision for doubtful accounts	3,075	3,928	8,348
Other expenses (income)	6,649	2,496	8,284
Total operating expenses	326,138	310,334	300,272
Other expense (income):
Interest expense, net of interest income of $2,442, $2,408, and $3,767 in 2011, 2010, and 2009, respectively	123,645	125,287	109,239
Loss (gain) on sale of properties in development	(2,404)	(993)	(19,357)
Provision for Impairment	13,772	26,615	97,519
Gains (Losses) on Extinguishment of Debt	0	4,243	2,784
(Income) loss from deferred compensation plan	206	(1,982)	(2,750)
Loss on derivatve instruments	54	(1,419)	3,294
Total other expense (income)	135,273	151,751	190,729
Income before equity in income (loss) of investments in real estate partnerships	39,006	14,076	(12,440)
Equity in income (loss) of investments in real estate partnerships	9,643	(12,884)	(26,373)
Income from continuing operations	48,649	1,192	(38,813)
Discontinued operations, net:
Operating (loss) income	1,197	4,232	3,942
(Loss) gain on sale of operating properties and properties in development	5,942	7,577	5,835
(Loss) income from discontinued operations	7,139	11,809	9,777
Net income	55,788	13,001	(29,036)
Noncontrolling interests:
Preferred units	(3,725)	(3,725)	(3,725)
Exchangeable operating partnership units	(103)	(84)	216
Limited partners' interest in consolidated partnerships	(590)	(376)	(452)
Net income attributable to noncontrolling interests	(4,418)	(4,185)	(3,961)
Net income attributable to controlling interests	51,370	8,816	(32,997)
Preferred stock dividends	(19,675)	(19,675)	(19,675)
Net income attributable to common stockholders	31,695	(10,859)	(52,672)
Income per common share/unit - basic:
Continuing operations	$ 0.27	$ (0.29)	$ (0.82)
Discontinued operations	$ 0.08	$ 0.15	$ 0.12
Net income attributable to common stockholders	$ 0.35	$ (0.14)	$ (0.70)
Income per common share/unit - diluted:
Continuing operations	$ 0.27	$ (0.28)	$ (0.82)
Discontinued operations	$ 0.08	$ 0.14	$ 0.12
Net income attributable to common stockholders	$ 0.35	$ (0.14)	$ (0.70)
Partnership Interest [Member]
Revenues
Minimum rent	356,097	338,639	337,516
Percentage rent	2,996	2,540	3,585
Recoveries from tenants and other income	107,344	105,582	99,171
Management, transaction, and other fees	33,980	29,400	38,289
Total revenues	500,417	476,161	478,561
Operating Expenses
Depreciation and amortization	132,129	120,450	114,058
Operating and maintenance	72,626	68,496	64,030
General and administrative	56,117	61,502	53,177
Real estate taxes	55,542	53,462	52,375
Provision for doubtful accounts	3,075	3,928	8,348
Other expenses (income)	6,649	2,496	8,284
Total operating expenses	326,138	310,334	300,272
Other expense (income):
Interest expense, net of interest income of $2,442, $2,408, and $3,767 in 2011, 2010, and 2009, respectively	123,645	125,287	109,239
Loss (gain) on sale of properties in development	(2,404)	(993)	(19,357)
Provision for Impairment	13,772	26,615	97,519
Gains (Losses) on Extinguishment of Debt	0	4,243	2,784
(Income) loss from deferred compensation plan	206	(1,982)	(2,750)
Loss on derivatve instruments	54	(1,419)	3,294
Total other expense (income)	135,273	151,751	190,729
Income before equity in income (loss) of investments in real estate partnerships	39,006	14,076	(12,440)
Equity in income (loss) of investments in real estate partnerships	9,643	(12,884)	(26,373)
Income from continuing operations	48,649	1,192	(38,813)
Discontinued operations, net:
Operating (loss) income	1,197	4,232	3,942
(Loss) gain on sale of operating properties and properties in development	5,942	7,577	5,835
(Loss) income from discontinued operations	7,139	11,809	9,777
Net income	55,788	13,001	(29,036)
Noncontrolling interests:
Limited partners' interest in consolidated partnerships	(590)	(376)	(452)
Net income attributable to noncontrolling interests	(590)	(376)	(452)
Net income attributable to controlling interests	55,198	12,625	(29,488)
Preferred unit distributions	(23,400)	(23,400)	(23,400)
Net income attributable to common unit holders	$ 31,798	$ (10,775)	$ (52,888)
Income per common share/unit - basic:
Continuing operations	$ 0.27	$ (0.29)	$ (0.82)
Discontinued operations	$ 0.08	$ 0.15	$ 0.12
Net income attributable to common unit holders	$ 0.35	$ (0.14)	$ (0.70)
Income per common share/unit - diluted:
Continuing operations	$ 0.27	$ (0.28)	$ (0.82)
Discontinued operations	$ 0.08	$ 0.14	$ 0.12