Consolidated Statements of Operations - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Document Fiscal Year Focus			2015
Discontinued operations, net:
Gain on sale of real estate	$ (27,755)	$ (27,558)	$ (34,215)	$ (29,598)
Parent Company [Member]
Revenues:
Minimum rent	105,071	98,620	308,766	290,935
Percentage rent	486	371	2,593	2,301
Recoveries from tenants and other income	30,725	28,787	94,205	90,144
Management, transaction, and other fees	5,786	5,781	18,032	18,353
Total revenues	142,068	133,559	423,596	401,733
Operating expenses:
Depreciation and amortization	37,032	36,417	109,249	110,345
Operating and maintenance	19,761	18,149	61,119	58,152
General and administrative	14,750	14,463	46,227	43,883
Real estate taxes	16,044	14,832	46,842	44,529
Other operating expenses	1,880	2,062	4,825	5,665
Total operating expenses	89,467	85,923	268,262	262,574
Other expense (income):
Interest expense, net	25,099	27,561	78,407	82,141
Provision for impairment	0	0	0	225
Early extinguishment of debt	0	0	61	0
Net investment loss (income), including unrealized losses of $1,296 and $472, and $1,771 and $289 for the three and nine months ended September 30, 2015 and 2014, respectively	1,190	(94)	190	(915)
Total other expense	26,289	27,467	78,536	81,451
Income from operations before equity in income of investments in real estate partnerships	26,312	20,169	76,798	57,708
Equity in income of investments in real estate partnerships	5,667	5,713	17,991	22,353
Income from operations	31,979	25,882	94,789	80,061
Discontinued operations, net:
Gain on sale of real estate	(27,755)	(27,558)	(34,215)	(29,598)
Net income	59,734	53,440	129,004	109,659
Noncontrolling interests:
Exchangeable operating partnership units	(94)	(90)	(204)	(185)
Limited partners’ interests in consolidated partnerships	(643)	(142)	(1,619)	(863)
Income attributable to noncontrolling interests	(737)	(232)	(1,823)	(1,048)
Net income attributable to the Company	58,997	53,208	127,181	108,611
Preferred stock dividends	(5,266)	(5,266)	(15,797)	(15,797)
Net income attributable to common stockholders	$ 53,731	$ 47,942	$ 111,384	$ 92,814
Income per common share/unit - basic:
Continuing operations (in dollars per share)	$ 0.57	$ 0.52	$ 1.18	$ 1.00
Income per common share/unit - diluted:
Continuing operations (in dollars per share)	$ 0.57	$ 0.52	$ 1.18	$ 1.00
Partnership Interest [Member]
Revenues:
Minimum rent	$ 105,071	$ 98,620	$ 308,766	$ 290,935
Percentage rent	486	371	2,593	2,301
Recoveries from tenants and other income	30,725	28,787	94,205	90,144
Management, transaction, and other fees	5,786	5,781	18,032	18,353
Total revenues	142,068	133,559	423,596	401,733
Operating expenses:
Depreciation and amortization	37,032	36,417	109,249	110,345
Operating and maintenance	19,761	18,149	61,119	58,152
General and administrative	14,750	14,463	46,227	43,883
Real estate taxes	16,044	14,832	46,842	44,529
Other operating expenses	1,880	2,062	4,825	5,665
Total operating expenses	89,467	85,923	268,262	262,574
Other expense (income):
Interest expense, net	25,099	27,561	78,407	82,141
Provision for impairment	0	0	0	225
Early extinguishment of debt	0	0	61	0
Net investment loss (income), including unrealized losses of $1,296 and $472, and $1,771 and $289 for the three and nine months ended September 30, 2015 and 2014, respectively	1,190	(94)	190	(915)
Total other expense	26,289	27,467	78,536	81,451
Income from operations before equity in income of investments in real estate partnerships	26,312	20,169	76,798	57,708
Equity in income of investments in real estate partnerships	5,667	5,713	17,991	22,353
Income from operations	31,979	25,882	94,789	80,061
Discontinued operations, net:
Gain on sale of real estate	(27,755)	(27,558)	(34,215)	(29,598)
Net income	59,734	53,440	129,004	109,659
Noncontrolling interests:
Limited partners’ interests in consolidated partnerships	(643)	(142)	(1,619)	(863)
Income attributable to noncontrolling interests	(643)	(142)	(1,619)	(863)
Net income attributable to the Company	59,091	53,298	127,385	108,796
Preferred unit distributions	(5,266)	(5,266)	(15,797)	(15,797)
Net income attributable to common unit holders	$ 53,825	$ 48,032	$ 111,588	$ 92,999
Income per common share/unit - basic:
Continuing operations (in dollars per share)	$ 0.57	$ 0.52	$ 1.18	$ 1.00
Income per common share/unit - diluted:
Continuing operations (in dollars per share)	$ 0.57	$ 0.52	$ 1.18	$ 1.00