CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014
CASH FLOWS FROM OPERATING ACTIVITIES
Net income	$ 201,744	$ 193,863
Adjustments to net income:
Depreciation and amortization	303,476	278,124
Income from discontinued operations		(3,097)
Amortization of share-based compensation	7,598	7,653
Non-cash rental adjustments	(6,462)	(5,390)
Amortization of net premiums on mortgages payable	(5,608)	(10,843)
Amortization of deferred financing costs	6,806	8,027
Loss on interest rate swaps	7,138	409
Gain on sales of real estate	(17,117)	(14,211)
Provisions for impairment on real estate	9,182	2,676
Cash provided by discontinued operations		1,310
Change in assets and liabilities
Accounts receivable and other assets	2,351	11,976
Accounts payable, accrued expenses and other liabilities	(36,160)	(30,416)
Net cash provided by operating activities	472,948	440,081
CASH FLOWS FROM INVESTING ACTIVITIES
Investment in real estate	(1,061,871)	(1,076,391)
Improvements to real estate, including leasing costs	(5,861)	(4,538)
Proceeds from sales of real estate:
Continuing operations	51,958	46,644
Discontinued operations		6,918
Collection of loans receivable		350
Restricted escrow deposits for Section 1031 tax-deferred exchanges and pending acquisitions	20,517	(27,340)
Net cash used in investing activities	(995,257)	(1,054,357)
CASH FLOWS FROM FINANCING ACTIVITIES
Cash distributions to common stockholders	(392,767)	(356,735)
Cash dividends to preferred stockholders	(20,310)	(31,447)
Borrowings on line of credit	1,059,000	1,359,121
Payments on line of credit	(843,000)	(1,442,121)
Proceeds from notes and bonds payable issued		598,594
Principal payments on mortgages payable	(140,825)	(77,619)
Proceeds from term loans	250,000
Proceeds from common stock offerings, net	276,430	528,615
Redemption of preferred units	(6,750)
Distributions to noncontrolling interests	(1,267)	(1,390)
Debt issuance costs	(10,358)	(5,609)
Proceeds from dividend reinvestment and stock purchase plan, net	360,941	56,580
Other items, including shares withheld upon vesting	(5,563)	(7,034)
Net cash provided by financing activities	525,531	620,955
Net increase in cash and cash equivalents	3,222	6,679
Cash and cash equivalents, beginning of period	3,852	10,257
Cash and cash equivalents, end of period	$ 7,074	$ 16,936