CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017
Cash flows from operating activities:
Net income	$ 396,133	$ 400,975
Adjustments to reconcile net income to cash provided by operating activities:
Depreciation expense	315,743	282,060
Amortization of deferred financing costs	4,042	3,873
Amortization of debt discount (premium)	849	(6,454)
Loss on extinguishment of debt, net	1,039	24,162
Amortization of stock-based compensation	10,127	9,658
Equity in loss (income) of, and return on, unconsolidated real estate entities and noncontrolling interests, net of eliminations	3,143	(4,473)
Casualty and impairment (gain) loss, net	(58)	11,688
Abandonment of development pursuits	725	388
Cash flow hedge losses reclassified to earnings	3,213	3,534
Gain on sale of real estate assets	(105,524)	(141,079)
Increase in resident security deposits, prepaid expenses and other assets	(3,875)	(13,174)
(Decrease) increase in accrued expenses, other liabilities and accrued interest payable	(260)	4,498
Net cash provided by operating activities	625,297	575,656
Cash flows from investing activities:
Development/redevelopment of real estate assets including land acquisitions and deferred development costs	(604,540)	(495,868)
Capital expenditures - existing real estate assets	(37,081)	(22,415)
Capital expenditures - non-real estate assets	(1,896)	(6,334)
Proceeds from sale of real estate, net of selling costs	299,226	270,481
Insurance proceeds for property damage claims	58	6,192
Mortgage note receivable lending	(2,291)	(11,069)
Mortgage note receivable payment	27,511	0
Increase (decrease) in payables for construction	7,421	(6,463)
Distributions from unconsolidated real estate entities	2,013	21,852
Investments in unconsolidated real estate entities	(7,102)	(10,100)
Net cash used in investing activities	(316,681)	(253,724)
Cash flows from financing activities:
Issuance of common stock, net	833	110,033
Dividends paid	(399,070)	(380,723)
Proceeds from Unsecured Lines of Credit	0	105,000
Proceeds from Notes Payable	0	185,100
Repayments of mortgage notes payable, including prepayment penalties	(59,314)	(1,287,048)
Issuance of unsecured notes	299,442	948,616
Payment of deferred financing costs	(3,345)	(11,466)
Payment of capital lease obligation	(535)	(18,422)
Receipts for termination of forward interest rate swaps	12,598	391
Payments related to tax withholding for share-based compensation	(10,524)	(10,441)
Distributions to DownREIT partnership unitholders	(22)	(21)
Contributions from joint venture and profit-sharing partners	0	1,038
Distributions to joint venture and profit-sharing partners	(208)	(213)
Preferred interest obligation redemption and dividends	(480)	(600)
Net cash used in financing activities	(160,625)	(358,756)
Net increase (decrease) in cash and cash equivalents	147,991	(36,824)
Cash and cash equivalents and restricted cash, beginning of period	201,906	329,977
Cash and cash equivalents and restricted cash, end of period	349,897	293,153
Cash paid during the period for interest, net of amount capitalized	95,204	102,624
Supplemental Cash Flow Information [Abstract]
Cash, cash equivalents and restricted cash reported in the Condensed Consolidated Statements of Cash Flows	$ 201,906	$ 329,977