Consolidated Statements Of Operations And Comprehensive Income (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Revenues:
Rentals, net	$ 491,369	$ 464,234	$ 458,750
Other	12,169	14,123	12,534
Total	503,538	478,357	471,284
Expenses:
Depreciation and amortization	140,983	131,350	125,302
Operating	98,426	89,998	90,881
Real estate taxes, net	58,077	55,522	53,173
Impairment loss	9,982	55,574	33,317
General and administrative	28,554	25,477	24,944
Total	336,022	357,921	327,617
Operating Income	167,516	120,436	143,667
Interest Expense, net	(115,812)	(139,717)	(145,391)
Interest and Other Income, net	6,048	5,062	9,823
Loss on Redemption of Convertible Senior Unsecured Notes	0	0	(135)
Gain on Sale of Real Estate Joint Venture and Partnership Interests	14,203	0	0
Equity in (Losses) Earnings of Real Estate Joint Ventures and Partnerships, net	(1,558)	7,834	12,889
Gain on Acquisition	1,869	0	0
(Provision) Benefit for Income Taxes	(79)	(146)	82
Income (Loss) from Continuing Operations	72,187	(6,531)	20,935
Operating Income from Discontinued Operations	10,611	11,318	27,205
Gain on Sale of Property from Discontinued Operations	68,589	10,273	1,093
Income from Discontinued Operations	79,200	21,591	28,298
Gain on Sale of Property	1,034	1,679	2,005
Net Income	152,421	16,739	51,238
Less: Net Income Attributable to Noncontrolling Interests	(5,781)	(1,118)	(5,032)
Net Income Adjusted for Noncontrolling Interests	146,640	15,621	46,206
Dividends on Preferred Shares	(34,930)	(35,476)	(35,476)
Redemption Costs of Preferred Shares	(2,500)	0	0
Net Income (Loss) Attributable to Common Shareholders	109,210	(19,855)	10,730
Earnings Per Common Share - Basic:
Income (loss) from continuing operations attributable to common shareholders	$ 0.25	$ (0.34)	$ (0.14)
Income from discontinued operations	$ 0.65	$ 0.17	$ 0.23
Net income (loss) attributable to common shareholders	$ 0.90	$ (0.17)	$ 0.09
Earnings Per Common Share - Diluted:
Income (loss) from continuing operations attributable to common shareholders	$ 0.25	$ (0.34)	$ (0.14)
Income from discontinued operations	$ 0.65	$ 0.17	$ 0.23
Net income (loss) attributable to common shareholders	$ 0.90	$ (0.17)	$ 0.09
Comprehensive Income:
Net Income	152,421	16,739	51,238
Other Comprehensive Income (Loss):
Net unrealized (loss) gain on derivatives	(123)	(854)	123
Amortization of loss on derivatives	2,650	2,551	2,566
Retirement liability adjustment	473	(7,666)	(505)
Total	3,000	(5,969)	2,184
Comprehensive Income	155,421	10,770	53,422
Comprehensive Income Attributable to Noncontrolling Interests	(5,781)	(1,118)	(5,032)
Comprehensive Income Adjusted for Noncontrolling Interests	$ 149,640	$ 9,652	$ 48,390