CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Revenue:
Rental and other income	$ 1,028,403	$ 926,431	$ 835,466
Management, development and other fees	10,257	9,656	7,354
Total revenue	1,038,660	936,087	842,820
Expenses:
Operating expenses, excluding property taxes	278,481	257,718	246,257
Property taxes	101,136	92,568	87,864
Interest expense, net	136,920	167,814	169,997
Loss on extinguishment of debt, net	1,179	1,940
Depreciation expense	256,026	239,060	220,563
General and administrative expense	34,101	29,371	26,846
Casualty and impairment loss	1,449	14,052
Total expenses	809,292	802,523	751,527
Equity in income of unconsolidated entities	20,914	5,120	762
Gain on sale of land	280	13,716
Gain on acquisition of unconsolidated entity	14,194
Income from continuing operations	264,756	152,400	92,055
Discontinued operations:
Income from discontinued operations	12,495	7,880	7,950
Gain on sale of real estate assets	146,311	281,090	74,074
Total discontinued operations	158,806	288,970	82,024
Net income	423,562	441,370	174,079
Net loss attributable to noncontrolling interests	307	252	1,252
Net income attributable to common stockholders	423,869	441,622	175,331
Other comprehensive income:
Unrealized loss on cash flow hedges	(22,876)	(85,845)	(108)
Cash flow hedge losses reclassified to earnings	1,889
Comprehensive income	$ 402,882	$ 355,777	$ 175,223
Earnings per common share - basic:
Income from continuing operations attributable to common stockholders (in dollars per share)	$ 2.71	$ 1.69	$ 1.10
Discontinued operations attributable to common stockholders (in dollars per share)	$ 1.63	$ 3.20	$ 0.98
Net income attributable to common stockholders (in dollars per share)	$ 4.34	$ 4.89	$ 2.08
Earnings per common share - diluted:
Income from continuing operations attributable to common stockholders (in dollars per share)	$ 2.70	$ 1.69	$ 1.10
Discontinued operations attributable to common stockholders (in dollars per share)	$ 1.62	$ 3.18	$ 0.97
Net income attributable to common stockholders (in dollars per share)	$ 4.32	$ 4.87	$ 2.07