Consolidated Statements of Operations - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Document Fiscal Year Focus			2015
Discontinued operations, net:
Gain on sale of real estate	$ (5,657)	$ (1,691)	$ (6,460)	$ (2,406)
Parent Company [Member]
Revenues:
Minimum rent	102,390	97,778	203,695	192,314
Percentage rent	300	545	2,108	1,930
Recoveries from tenants and other income	32,431	30,316	63,479	61,357
Management, transaction, and other fees	6,008	6,253	12,246	12,572
Total revenues	141,129	134,892	281,528	268,173
Operating expenses:
Depreciation and amortization	36,225	36,023	72,218	73,929
Operating and maintenance	20,185	19,498	41,358	40,003
General and administrative	15,099	15,223	31,477	29,421
Real estate taxes	15,667	14,898	30,798	29,697
Other operating expenses	1,779	1,795	2,943	3,968
Total operating expenses	88,955	87,437	178,794	177,018
Other expense (income):
Interest expense, net	26,675	27,445	53,308	54,580
Provision for impairment	0	0	0	225
Early extinguishment of debt	0	0	61	0
Net investment income, including unrealized losses (gains) of $892 and ($290), and $475 and ($183) for the three and six months ended June 30, 2015 and 2014, respectively	(367)	(628)	(1,000)	(821)
Total other expense	26,308	26,817	52,247	53,984
Income from operations before equity in income of investments in real estate partnerships	25,866	20,638	50,487	37,171
Equity in income of investments in real estate partnerships	6,757	8,832	12,324	16,640
Income from operations	32,623	29,470	62,811	53,811
Discontinued operations, net:
Gain on sale of real estate	(5,657)	(1,691)	(6,460)	(2,406)
Net income	38,280	31,161	69,271	56,217
Noncontrolling interests:
Exchangeable operating partnership units	(61)	(53)	(110)	(95)
Limited partners’ interests in consolidated partnerships	(473)	(360)	(977)	(719)
Income attributable to noncontrolling interests	(534)	(413)	(1,087)	(814)
Net income attributable to the Company	37,746	30,748	68,184	55,403
Preferred stock dividends	(5,266)	(5,266)	(10,531)	(10,531)
Net income attributable to common stockholders	$ 32,480	$ 25,482	$ 57,653	$ 44,872
Income per common share/unit - basic:
Continuing operations (in dollars per share)	$ 0.35	$ 0.28	$ 0.61	$ 0.48
Income per common share/unit - diluted:
Continuing operations (in dollars per share)	$ 0.34	$ 0.28	$ 0.61	$ 0.48
Partnership Interest [Member]
Revenues:
Minimum rent	$ 102,390	$ 97,778	$ 203,695	$ 192,314
Percentage rent	300	545	2,108	1,930
Recoveries from tenants and other income	32,431	30,316	63,479	61,357
Management, transaction, and other fees	6,008	6,253	12,246	12,572
Total revenues	141,129	134,892	281,528	268,173
Operating expenses:
Depreciation and amortization	36,225	36,023	72,218	73,929
Operating and maintenance	20,185	19,498	41,358	40,003
General and administrative	15,099	15,223	31,477	29,421
Real estate taxes	15,667	14,898	30,798	29,697
Other operating expenses	1,779	1,795	2,943	3,968
Total operating expenses	88,955	87,437	178,794	177,018
Other expense (income):
Interest expense, net	26,675	27,445	53,308	54,580
Provision for impairment	0	0	0	225
Early extinguishment of debt	0	0	61	0
Net investment income, including unrealized losses (gains) of $892 and ($290), and $475 and ($183) for the three and six months ended June 30, 2015 and 2014, respectively	(367)	(628)	(1,000)	(821)
Total other expense	26,308	26,817	52,247	53,984
Income from operations before equity in income of investments in real estate partnerships	25,866	20,638	50,487	37,171
Equity in income of investments in real estate partnerships	6,757	8,832	12,324	16,640
Income from operations	32,623	29,470	62,811	53,811
Discontinued operations, net:
Gain on sale of real estate	(5,657)	(1,691)	(6,460)	(2,406)
Net income	38,280	31,161	69,271	56,217
Noncontrolling interests:
Limited partners’ interests in consolidated partnerships	(473)	(360)	(977)	(719)
Income attributable to noncontrolling interests	(473)	(360)	(977)	(719)
Net income attributable to the Company	37,807	30,801	68,294	55,498
Preferred unit distributions	(5,266)	(5,266)	(10,531)	(10,531)
Net income attributable to common unit holders	$ 32,541	$ 25,535	$ 57,763	$ 44,967
Income per common share/unit - basic:
Continuing operations (in dollars per share)	$ 0.35	$ 0.28	$ 0.61	$ 0.48
Income per common share/unit - diluted:
Continuing operations (in dollars per share)	$ 0.34	$ 0.28	$ 0.61	$ 0.48