CONSOLIDATED STATEMENTS OF CASH FLOWS (unaudited) (USD $)	9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010
CASH FLOWS FROM OPERATING ACTIVITIES
Net income	$ 116,027,000	$ 92,907,000
Adjustments to net income:
Depreciation and amortization	87,542,000	70,145,000
Income from discontinued operations	(4,460,000)	(5,276,000)
Gain on sale of land	(210,000)	0
Amortization of share-based compensation	6,098,000	4,824,000
Amortization of net premiums on mortgages payable	(98,000)	0
Provision for impairment on real estate held for investment	10,000	0
Cash provided by discontinued operations:
Real estate	773,000	2,055,000
Collection of principal on notes receivable	110,000	103,000
Change in assets and liabilities:
Accounts receivable and other assets	8,672,000	7,023,000
Accounts payable, accrued expenses and other liabilities	(15,217,000)	(15,020,000)
Net cash provided by operating activities	199,247,000	156,761,000
CASH FLOWS FROM INVESTING ACTIVITIES
Acquisition of income producing investment properties	(766,148,000)	(304,615,000)
Proceeds from the sales of real estate:
Continuing operations	783,000	0
Discontinued operations	11,692,000	15,294,000
Restricted escrow deposits	(2,830,000)	(5,687,000)
Net cash used in investing activities	(756,503,000)	(295,008,000)
CASH FLOWS FROM FINANCING ACTIVITIES
Cash distributions to common stockholders	(161,276,000)	(134,700,000)
Cash dividends to preferred stockholders	(18,190,000)	(18,190,000)
Borrowings under line of credit	378,100,000	408,700,000
Payments on line of credit	(281,500,000)	(413,300,000)
Principal payments on mortgages	(138,000)	0
Proceeds from common stock offerings, net	489,236,000	196,899,000
Proceeds from bonds issued, net of financing costs of $9,923	140,077,000	0
Proceeds from notes issued, net of financing costs of $3,869	0	246,131,000
Proceeds from dividend reinvestment and stock purchase plan, net	1,242,000	0
Other items	(2,359,000)	(1,737,000)
Net cash provided by financing activities	545,192,000	283,803,000
Net increase (decrease) in cash and cash equivalents	(12,064,000)	145,556,000
Cash and cash equivalents, beginning of period	17,607,000	10,026,000
Cash and cash equivalents, end of period	$ 5,543,000	$ 155,582,000