Condensed Consolidated Statements of Operations and Other Comprehensive Income (Loss) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Revenues:
Rental income	$ 116,811	$ 116,062	$ 350,390	$ 349,828
Tenant recovery income	26,519	27,703	79,486	79,692
Other property income	1,962	2,280	7,532	7,861
Total revenues	145,292	146,045	437,408	437,381
Expenses:
Property operating expenses	23,089	23,077	70,860	74,673
Real estate taxes	19,503	19,273	57,972	57,196
Depreciation and amortization	56,527	57,286	170,009	171,601
Provision for impairment of investment properties	10,660	0	11,983	0
Loss on lease terminations	1,689	1,392	6,550	8,085
General and administrative expenses	7,227	5,011	18,691	16,382
Total expenses	118,695	106,039	336,065	327,937
Operating income	26,597	40,006	101,343	109,444
Dividend income	302	578	1,782	1,776
Interest income	16	157	56	507
Gain on extinguishment of debt	0	991	3,879	15,429
Equity in loss of unconsolidated joint ventures, net	(1,863)	(1,869)	(5,467)	(6,028)
Interest expense	(49,456)	(56,903)	(142,333)	(170,121)
Co-venture obligation expense	0	(1,791)	(3,300)	(5,375)
Recognized gain on marketable securities	9,108	0	16,373	277
Other income (expense), net	726	567	(342)	1,323
Loss from continuing operations	(14,570)	(18,264)	(28,009)	(52,768)
Discontinued operations:
Loss, net	(11,788)	(378)	(9,725)	(28,830)
Gain on sales of investment properties, net	8,756	14,517	16,518	18,678
(Loss) income from discontinued operations	(3,032)	14,139	6,793	(10,152)
Gain (loss) on sales of investment properties, net	1,650	(891)	6,652	4,171
Net loss	(15,952)	(5,016)	(14,564)	(58,749)
Net income attributable to noncontrolling interests	0	(7)	0	(23)
Net loss attributable to Company shareholders	(15,952)	(5,023)	(14,564)	(58,772)
(Loss) earnings per common share - basic and diluted:
Continuing operations	$ (0.06)	$ (0.10)	$ (0.10)	$ (0.25)
Discontinued operations	$ (0.01)	$ 0.07	$ 0.03	$ (0.06)
Net loss per common share attributable to Company shareholders	$ (0.07)	$ (0.03)	$ (0.07)	$ (0.31)
Net loss	(15,952)	(5,016)	(14,564)	(58,749)
Other comprehensive loss:
Net unrealized (loss) gain on derivative instruments	(981)	(140)	(591)	971
Net unrealized gain (loss) on marketable securities	1,426	(6,240)	5,070	(3,843)
Reversal of unrealized gain to recognized gain on marketable securities	(9,108)	0	(16,373)	(277)
Comprehensive loss	(24,615)	(11,396)	(26,458)	(61,898)
Comprehensive income attributable to noncontrolling interests	0	(7)	0	(23)
Comprehensive loss attributable to Company shareholders	$ (24,615)	$ (11,403)	$ (26,458)	$ (61,921)
Weighted average number of common shares outstanding - basic and diluted	230,597	192,779	217,087	192,127