CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Cash flows from operating activities:
Net income	$ 827,706	$ 786,103	$ 974,175
Adjustments to reconcile net income to cash provided by operating activities:
Depreciation expense	707,331	661,578	631,196
Amortization of deferred financing costs	7,454	7,346	7,939
Amortization of debt discount	1,880	1,591	1,701
Loss on extinguishment of debt, net	9,333	602	17,492
Amortization of stock-based compensation	21,603	25,621	20,280
Equity in loss of, and return on, unconsolidated real estate entities and noncontrolling interests, net of eliminations	8,673	12,278	6,583
Casualty and impairment gain, net	0	0	826
Abandonment of development pursuits	9,262	2,943	501
Unrealized Gain (Loss) on Derivatives	(2,894)	0	0
Cash flow hedge losses reclassified to earnings	8,984	6,571	6,143
Gain on sale of real estate assets	(346,041)	(172,332)	(385,976)
Gain (Loss) on Sale of Other Investments	(8,213)	0	0
(Increase) decrease in resident security deposits, prepaid expenses and other assets	(28,675)	(19,118)	12,583
Increase in accrued expenses, other liabilities and accrued interest payable	3,212	8,621	7,668
Net cash provided by operating activities	1,219,615	1,321,804	1,301,111
Cash flows from investing activities:
Development/redevelopment of real estate assets including land acquisitions and deferred development costs	(843,907)	(1,052,011)	(1,139,954)
Acquisition of real estate assets, including partnership interest	0	(420,517)	(338,620)
Capital expenditures - existing real estate assets	(108,531)	(135,626)	(83,607)
Payments for Capital Improvements, Non Real Estate	(28,505)	(5,266)	(3,325)
Increase (decrease) in payables for construction	1,474	(4,848)	11,606
Proceeds from sale of real estate, net of selling costs	619,773	422,041	883,313
Proceeds from Sale of Other Real Estate	202,033	0	0
Mortgage note receivable lending	(258)	(692)	(3,699)
Mortgage note receivable payments	3,419	2,779	53,136
Distributions from unconsolidated real estate entities	11,157	10,454	35,516
Investments in unconsolidated real estate entities	(36,088)	(10,183)	(11,017)
Net cash used in investing activities	(179,433)	(1,193,869)	(596,651)
Cash flows from financing activities:
Issuance of common stock, net	3,464	409,725	52,261
Payments for Repurchase of Common Stock	(183,876)	0
Payments of Ordinary Dividends	(883,212)	(839,646)	(805,239)
Proceeds from Secured Notes Payable	51,000	30,250	295,939
Repayments of mortgage notes payable, including prepayment penalties	(126,712)	(227,570)	(255,452)
Issuance of unsecured notes	1,296,581	449,804	299,442
Repayment of unsecured notes, including prepayment penalties	(958,680)	0	(258,579)
Payment of deferred financing costs	(11,277)	(10,909)	(16,258)
Finance Lease, Principal Payments	0	0	(1,070)
(Payment) receipt for termination of forward interest rate swaps	(25,135)	(12,309)	12,598
Proceeds from (Payments to) Noncontrolling Interests	(68)	456	0
Payments related to tax withholding for share-based compensation	(14,917)	(16,101)	(10,556)
Distributions to DownREIT partnership unitholders	(48)	(46)	(44)
Payments of Distributions to Affiliates	(384)	(439)	(424)
Preferred interest obligation redemption and dividends	(1,000)	(1,400)	(1,120)
Net cash used in financing activities	(854,264)	(218,185)	(688,502)
Net increase in cash, cash equivalents and cash in escrow	185,918	(90,250)	15,958
Cash and cash equivalents and restricted cash, beginning of year	127,614	217,864	201,906
Cash and cash equivalents and restricted cash, end of year	313,532	127,614	217,864
Cash paid during the year for interest, net of amount capitalized	196,848	187,570	201,659
Supplemental Cash Flow Information [Abstract]
Cash and cash equivalents and restricted cash, end of year	$ 313,532	$ 127,614	$ 201,906