CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011
Net income	$ 214,430	$ 73,728
Adjustments to reconcile net income to cash provided by operating activities:
Depreciation expense	127,436	120,059
Depreciation expense from discontinued operations	895	4,160
Amortization of deferred financing costs and debt premium/discount	3,040	3,485
Amortization of stock-based compensation	4,268	3,262
Loss on extinguishment of debt	1,781
Equity in (income) loss of unconsolidated entities and noncontrolling interests, net of eliminations	(3,182)	421
Gain on sale of real estate assets	(95,329)	(7,675)
Expensed acquisition costs	163	958
Increase in cash in operating escrows	(1,988)	(1,144)
Increase in resident security deposits, prepaid expenses and other assets	(20,895)	(9,943)
Increase (decrease) in accrued expenses, other liabilities and accrued interest payable	(8,151)	18,568
Net cash provided by operating activities	222,468	205,879
Cash flows from investing activities:
Development/redevelopment of real estate assets including land acquisitions and deferred development costs	(341,144)	(266,374)
Acquisition of real estate assets	(37,105)	(46,275)
Capital expenditures - existing real estate assets	(6,606)	(7,765)
Capital expenditures - non-real estate assets	(588)	(7,748)
Proceeds from exchange/sale of real estate, net of selling costs	182,225	22,371
Increase (decrease) in payables for construction	6,582	(612)
Decrease in cash in construction escrows	1,697	10,917
Decrease in investments in unconsolidated real estate entities	2,188	2,458
Net cash used in investing activities	(192,751)	(293,028)
Cash flows from financing activities:
Issuance of common stock	175,682	264,134
Dividends paid	(177,322)	(154,382)
Repayments of mortgage notes payable	(103,621)	(31,963)
Repayment of unsecured notes	(179,400)
Payment of deferred financing costs	(123)	(252)
Acquisition of joint venture partner equity interest	(3,350)	(6,570)
Distributions to DownREIT partnership unitholders	(15)	(13)
Distributions to joint venture and profit-sharing partners	(158)	(127)
Net cash (used in) provided by financing activities	(288,307)	70,827
Net decrease in cash and cash equivalents	(258,590)	(16,322)
Cash and cash equivalents, beginning of period	616,853	306,426
Cash and cash equivalents, end of period	358,263	290,104
Cash paid during the period for interest, net of amount capitalized	$ 62,012	$ 76,315