CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Cash flows from operating activities:
Net income	$ 486,592	$ 618,432
Adjustments to reconcile net income to cash provided by operating activities:
Depreciation expense	529,508	490,213
Amortization of deferred financing costs	5,617	5,458
Amortization of debt discount	1,321	1,186
(Gain) loss on extinguishment of debt, net	9,333	602
Amortization of stock-based compensation	17,753	20,810
Equity in loss of, and return on, unconsolidated real estate entities and noncontrolling interests, net of eliminations	5,204	10,787
Abandonment of development pursuits	2,095	1,080
Cash flow hedge losses reclassified to earnings	6,617	4,825
Gain on sale of real estate assets	(96,823)	(166,223)
Gain on for-sale condominiums	(8,174)	0
Increase in resident security deposits, prepaid expenses and other assets	(36,332)	(29,804)
Increase in accrued expenses, other liabilities and accrued interest payable	39,363	57,556
Net cash provided by operating activities	962,074	1,014,922
Cash flows from investing activities:
Development/redevelopment of real estate assets including land acquisitions and deferred development costs	(562,334)	(791,551)
Acquisition of real estate assets, including partnership interest	0	(286,804)
Capital expenditures - existing real estate assets	(76,860)	(92,825)
Capital expenditures - non-real estate assets	(24,720)	(4,223)
Mortgage note receivable payments	(4,095)	(3,390)
Decrease in payables for construction	186,090	421,735
Proceeds from the sale of for-sale condominiums, net of selling costs	170,604	0
Mortgage note receivable lending	(260)	(565)
Mortgage note receivable payments	3,419	978
Proceeds from Sale of Equity Method Investments	9,877	694
Investments in unconsolidated real estate entities	(23,044)	(1,253)
Net cash used in investing activities	(321,323)	(757,204)
Cash flows from financing activities:
Issuance of common stock, net	1,599	207,789
Payments for Repurchase of Common Stock	(137,458)	0
Dividends paid	(661,000)	(627,467)
Issuance of mortgage notes payable	51,000	30,250
Repayments of mortgage notes payable, including prepayment penalties	(125,427)	(160,709)
Issuance of unsecured notes	1,296,581	449,804
Repayment of unsecured notes, including prepayment penalties	(958,681)	0
Payment of deferred financing costs	(11,278)	(10,910)
Payment for termination of forward interest rate swaps	(25,135)	(12,309)
(Payment to) contribution from noncontrolling interest	(59)	455
Payments related to tax withholding for share-based compensation	(14,752)	(15,961)
Distributions to DownREIT partnership unitholders	(36)	(34)
Distributions to joint venture and profit-sharing partners	(319)	(336)
Preferred interest obligation redemption and dividends	(1,000)	(1,400)
Net cash used in financing activities	(585,965)	(140,828)
Net increase in cash, cash equivalents and cash in escrow	54,786	116,890
Cash, cash equivalents and cash in escrow, beginning of period	127,614	217,864
Cash, cash equivalents and cash in escrow, end of period	182,400	334,754
Cash paid during the period for interest, net of amount capitalized	133,913	114,400
Supplemental Cash Flow Information [Abstract]
Cash, cash equivalents and cash in escrow reported in the Condensed Consolidated Statements of Cash Flows	$ 182,400	$ 334,754