CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Cash flows from operating activities:
Net income	$ 75,469	$ 57,609
Adjustments to reconcile net income to cash provided by operating activities:
Depreciation expense	109,829	61,571
Depreciation expense from discontinued operations		1,741
Amortization of deferred financing costs and debt (premium) discount	(1,604)	1,475
Amortization of stock-based compensation	2,099	1,984
Equity in (income) loss of, and return on, unconsolidated entities and noncontrolling interests, net of eliminations	16,734	(1,346)
Loss on extinguishment of debt, net		1,179
Gain on sale of real estate assets	(84,491)
Increase in cash in operating escrows	(6,758)	(1,225)
Increase in resident security deposits, prepaid expenses and other assets	(23,299)	(8,167)
Decrease in accrued expenses, other liabilities and accrued interest payable	(6,591)	(9,481)
Net cash provided by operating activities	81,388	105,340
Cash flows from investing activities:
Development/redevelopment of real estate assets including land acquisitions and deferred development costs	(221,274)	(159,091)
Acquisition of real estate assets, including partnership interest	(749,275)	(7,442)
Capital expenditures - existing real estate assets	(1,852)	(2,746)
Capital expenditures - non-real estate assets	(1,764)	(147)
Proceeds from sale of real estate, net of selling costs	327,922
Increase (decrease) in payables for construction	(360)	7,014
Decrease in cash in construction escrows		1,731
Increase in investments in unconsolidated real estate entities	(2,978)	(5,659)
Net cash used in investing activities	(649,581)	(166,340)
Cash flows from financing activities:
Issuance of common stock	253	8,956
Dividends paid	(110,891)	(84,926)
Repayments of mortgage notes payable, including prepayment penalties	(1,507,243)	(52,038)
Repayment of unsecured notes	(100,000)	(179,400)
Payment of deferred financing costs and issuance discounts		(123)
Distributions to DownREIT partnership unitholders	(8)	(7)
Distributions to joint venture and profit-sharing partners	(80)	(73)
Net cash used by financing activities	(1,717,969)	(307,611)
Net decrease in cash and cash equivalents	(2,286,162)	(368,611)
Cash and cash equivalents, beginning of period	2,733,618	616,853
Cash and cash equivalents, end of period	447,456	248,242
Cash paid during the period for interest, net of amount capitalized	$ 45,765	$ 42,684