CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Revenue:
Rental and other income	$ 256,035	$ 233,249	$ 504,052	$ 457,652
Management, development and other fees	2,770	2,332	5,319	4,652
Total revenue	258,805	235,581	509,371	462,304
Expenses:
Operating expenses, excluding property taxes	68,972	63,951	134,471	127,274
Property taxes	25,182	23,266	49,457	47,167
Interest expense, net	33,193	44,544	66,819	87,515
Loss on extinguishment of debt, net			1,179
Depreciation expense	64,875	60,836	127,436	120,059
General and administrative expense	8,316	8,145	18,026	15,437
Total expenses	200,538	200,742	397,388	397,452
Equity in income of unconsolidated entities	2,073	395	4,248	898
Gain on sale of land	280		280
Income from continuing operations	60,620	35,234	116,511	65,750
Discontinued operations:
Income from discontinued operations	1,152	283	2,870	303
Gain on sale of real estate assets	95,049	7,675	95,049	7,675
Total discontinued operations	96,201	7,958	97,919	7,978
Net income	156,821	43,192	214,430	73,728
Net (income) loss attributable to noncontrolling interests	88	181	237	(15)
Net income attributable to common stockholders	156,909	43,373	214,667	73,713
Other comprehensive income:
Unrealized loss on cash flow hedges	(27,798)	(19,336)	(16,789)	(19,420)
Comprehensive income	$ 129,111	$ 24,037	$ 197,878	$ 54,293
Earnings per common share - basic:
Income from continuing operations attributable to common stockholders (in dollars per share)	$ 0.63	$ 0.41	$ 1.22	$ 0.76
Discontinued operations attributable to common stockholders (in dollars per share)	$ 1.01	$ 0.09	$ 1.03	$ 0.09
Net income attributable to common stockholders (in dollars per share)	$ 1.64	$ 0.50	$ 2.25	$ 0.85
Earnings per common share - diluted:
Income from continuing operations attributable to common stockholders (in dollars per share)	$ 0.63	$ 0.40	$ 1.22	$ 0.75
Discontinued operations attributable to common stockholders (in dollars per share)	$ 1.00	$ 0.09	$ 1.02	$ 0.09
Net income attributable to common stockholders (in dollars per share)	$ 1.63	$ 0.49	$ 2.24	$ 0.84
Dividends per common share: (in dollars per share)	$ 0.9700	$ 0.8925	$ 1.9400	$ 1.7850