CONSOLIDATED STATEMENTS OF CASH FLOWS (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012
Cash flows from operating activities:
Net income	$ 124,349	$ 79,579
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	133,097	128,030
Gain on disposition of property	(45,004)	(19,667)
Stock-based compensation	7,788	12,214
Changes in assets and liabilities:
Cash in escrows, net	613	(1,194)
Other assets	(3,287)	(9,401)
Accounts payable and accrued liabilities	2,027	8,025
Total adjustments	95,234	118,007
Net cash provided by operating activities	219,583	197,586
Cash flows from investing activities:
Purchase of properties, net of mortgage notes assumed		(289,759)
Purchase of land for development	(28,088)
Capital improvements to properties including redevelopment	(107,848)	(120,511)
Additions to construction in progress	(47,971)	(39,324)
Additions to predevelopment	(375)	(440)
Proceeds from sale of properties, net	120,644	40,080
Withdrawals from (additions to) cash held in escrow, net	1,428	(40,050)
Net cash used in investing activities	(62,210)	(450,004)
Cash flows from financing activities:
Proceeds from sale of common stock, net	46,593	159,891
Proceeds from issuance of common stock through public offering, net	267,633
Repurchase of common stock	(3,075)	(4,186)
Scheduled payments of mortgage notes payable	(25,777)	(26,829)
Payoff mortgage notes payable	(260,160)	(32,863)
Proceeds from unsecured notes payable	25,000	150,000
Payments of unsecured notes payable	(25,000)
Proceeds from unsecured line of credit	565,000	407,500
Payments on unsecured line of credit	(621,000)	(282,000)
Payments of deferred loan costs	(2,090)	(356)
Additions to cash held in escrow, net		(358)
Dividends and distributions paid	(134,565)	(118,483)
Net cash provided by (used in) financing activities	(167,441)	252,316
Net decrease in cash and cash equivalents	(10,068)	(102)
Cash and cash equivalents:
Beginning of year	21,092	8,297
End of period	11,024	8,195
Supplemental disclosure:
Interest capitalized	5,208	3,267
Supplemental disclosure of non-cash investing and financing activities:
Mortgage loan assumed associated with property acquisition		7,284
Exchange of UPREIT Units for common stock	2,866	3,538
Transfers of construction in progress to land and buildings, improvements and equipment	117	42,388
Additions to properties and construction in progress included in accounts payable	$ 6,503	$ 10,910