Consolidated Statements of Operations (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Other expense (income):
Income tax expense of taxable REIT subsidiary		$ 231
Discontinued operations, net:
Gain on sale of operating properties, net		6,301
Parent Company [Member]
Revenues:
Minimum rent	90,726	91,395
Percentage rent	1,548	1,160
Recoveries from tenants and other income	27,053	26,538
Management, transaction, and other fees	6,761	7,150
Total revenues	126,088	126,243
Operating expenses:
Depreciation and amortization	32,764	32,480
Operating and maintenance	17,909	18,484
General and administrative	17,975	16,122
Real estate taxes	13,898	15,145
Other expenses	1,523	1,358
Total operating expenses	84,069	83,589
Other expense (income):
Interest expense, net of interest income of $459 and $535 in 2013 and 2012, respectively	27,832	28,958
Net investment income from deferred compensation plan, including unrealized gains of $831 and $1,224 in 2013 and 2012, respectively	(1,071)	(1,528)
Total other expense	26,761	27,430
Income before equity in income of investments in real estate partnerships	15,258	15,224
Equity in income of investments in real estate partnerships	5,876	2,966
Income from continuing operations before tax	21,134	18,190
Income tax expense of taxable REIT subsidiary	0	231
Income from continuing operations	21,134	17,959
Discontinued operations, net:
Operating income	0	641
Gain on sale of operating properties, net	0	6,301
Income from discontinued operations	0	6,942
Income before gain on sale of real estate	21,134	24,901
Gain on sale of real estate	0	1,834
Net income	21,134	26,735
Noncontrolling interests:
Preferred units	0	629
Exchangeable operating partnership units	(39)	(54)
Limited partners’ interests in consolidated partnerships	(275)	(192)
(Income) loss attributable to noncontrolling interests	(314)	383
Net income attributable to the Company	20,820	27,118
Preferred stock dividends	(5,266)	(13,937)
Net Income (Loss) attributable to Common Stockholders	15,554	13,181
Income per common share/unit - basic:
Continuing operations (in dollars per share)	$ 0.17	$ 0.07
Discontinued operations (in dollars per share)	$ 0.00	$ 0.07
Net income attributable to common stockholders (in dollars per share)	$ 0.17	$ 0.14
Income per common share/unit - diluted:
Continuing operations (in dollars per share)	$ 0.17	$ 0.07
Discontinued operations (in dollars per share)	$ 0.00	$ 0.07
Net income attributable to common stockholders (in dollars per share)	$ 0.17	$ 0.14
Partnership Interest [Member]
Revenues:
Minimum rent	90,726	91,395
Percentage rent	1,548	1,160
Recoveries from tenants and other income	27,053	26,538
Management, transaction, and other fees	6,761	7,150
Total revenues	126,088	126,243
Operating expenses:
Depreciation and amortization	32,764	32,480
Operating and maintenance	17,909	18,484
General and administrative	17,975	16,122
Real estate taxes	13,898	15,145
Other expenses	1,523	1,358
Total operating expenses	84,069	83,589
Other expense (income):
Interest expense, net of interest income of $459 and $535 in 2013 and 2012, respectively	27,832	28,958
Net investment income from deferred compensation plan, including unrealized gains of $831 and $1,224 in 2013 and 2012, respectively	(1,071)	(1,528)
Total other expense	26,761	27,430
Income before equity in income of investments in real estate partnerships	15,258	15,224
Equity in income of investments in real estate partnerships	5,876	2,966
Income from continuing operations before tax	21,134	18,190
Income tax expense of taxable REIT subsidiary	0	231
Income from continuing operations	21,134	17,959
Discontinued operations, net:
Operating income	0	641
Gain on sale of operating properties, net	0	6,301
Income from discontinued operations	0	6,942
Income before gain on sale of real estate	21,134	24,901
Gain on sale of real estate	0	1,834
Net income	21,134	26,735
Noncontrolling interests:
Limited partners’ interests in consolidated partnerships	(275)	(192)
(Income) loss attributable to noncontrolling interests	(275)	(192)
Net income attributable to the Company	20,859	26,543
Preferred unit distributions	(5,266)	(13,308)
Net income attributable to common unit holders	15,593	13,235
Income per common share/unit - basic:
Continuing operations (in dollars per share)	0.17	0.07
Discontinued operations (in dollars per share)	0.00	0.07
Net income attributable to common unit holders (in dollars per share)	0.17	0.14
Income per common share/unit - diluted:
Continuing operations (in dollars per share)	0.17	0.07
Discontinued operations (in dollars per share)	0.00	0.07
Net income attributable to common unit holders (in dollars per share)	0.17	0.14
Segment, Continuing Operations [Member] | Parent Company [Member]
Noncontrolling interests:
(Income) loss attributable to noncontrolling interests	(314)	383
Segment, Continuing Operations [Member] | Partnership Interest [Member]
Noncontrolling interests:
(Income) loss attributable to noncontrolling interests	$ (275)	$ (192)