CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011
Net income	$ 301,178	$ 118,405
Adjustments to reconcile net income to cash provided by operating activities:
Depreciation expense	193,434	180,953
Depreciation expense from discontinued operations	895	6,002
Amortization of deferred financing costs and debt premium/discount	4,122	4,888
Loss on extinguishment of debt	1,781
Amortization of stock-based compensation	8,548	5,390
Equity in income of unconsolidated entities and noncontrolling interests, net of eliminations	(7,484)	(1,177)
Impairment loss		14,052
Gain on sale of real estate assets	(95,329)	(21,391)
Gain on acquisition of unconsolidated entity	(14,194)
Expensed acquisition costs		1,010
(Increase)/decrease in cash in operating escrows	6,644	(2,553)
Increase in resident security deposits, prepaid expenses and other assets	(8,069)	(17,683)
(Decrease) increase in accrued expenses, other liabilities and accrued interest payable	(16,353)	7,116
Net cash provided by operating activities	375,173	295,012
Cash flows from investing activities:
Development/redevelopment of real estate assets including land acquisitions and deferred development costs	(567,867)	(456,965)
Acquisition of real estate assets	(105,904)	(46,275)
Capital expenditures - existing real estate assets	(13,449)	(14,838)
Capital expenditures - non-real estate assets	(1,094)	(7,911)
Proceeds from exchange/sale of real estate, net of selling costs	182,225	55,479
Increase in payables for construction	14,419	1,770
Decrease in cash in construction escrows	16,944	13,421
Increase in investments in unconsolidated real estate entities	(8,006)	(14,163)
Net cash used in investing activities	(482,732)	(469,482)
Cash flows from financing activities:
Issuance of common stock	326,653	1,037,630
Dividends paid	(270,866)	(233,427)
Repayments of mortgage notes payable	(106,255)	(42,648)
Issuance of unsecured notes	450,000
Settlement of interest rate contract	(54,930)
Repayment of unsecured notes	(179,400)	(189,900)
Payment of deferred financing costs	(6,744)	(5,996)
Acquisition of joint venture partner equity interest	(3,350)	(6,570)
Distributions to DownREIT partnership unitholders	(22)	(20)
Distributions to joint venture and profit-sharing partners	(247)	(194)
Net cash provided by financing activities	154,839	558,875
Net increase in cash and cash equivalents	47,280	384,405
Cash and cash equivalents, beginning of period	616,853	305,644
Cash and cash equivalents, end of period	664,133	690,049
Cash paid during the period for interest, net of amount capitalized	$ 101,121	$ 129,005