AvalonBay Communities (AVB) 10-Q 4 Nov 21 2021 Q3 Quarterly report Financial data

Cover Page

Cover Page - shares	9 Months Ended
	Sep. 30, 2021	Oct. 29, 2021
Cover [Abstract]
Document Type	10-Q
Document Period End Date	Sep. 30, 2021
Entity File Number	1-12672
Entity Registrant Name	AVALONBAY COMMUNITIES, INC.
Entity Incorporation, State or Country Code	MD
Entity Tax Identification Number	77-0404318
Entity Address, Address Line One	4040 Wilson Blvd., Suite 1000
Entity Address, Address City or Town	Arlington
Entity Address, State or Province	VA
Entity Address, Postal Zip Code	22203
City Area Code	703
Local Phone Number	329-6300
Title of 12(b) Security	Common Stock, par value $0.01 per share
Trading Symbol	AVB
Security Exchange Name	NYSE
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		139,740,922
Entity Central Index Key	0000915912
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	Q3
Amendment Flag	false
Document Quarterly Report	true
Document Transition Report	false

CONDENSED CONSOLIDATED BALANCE

CONDENSED CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Real estate:
Land and improvements	$ 4,510,361	$ 4,394,298
Buildings and improvements	17,839,750	17,231,275
Furniture, fixtures and equipment	1,000,756	924,583
Gross operating real estate	23,350,867	22,550,156
Less accumulated depreciation	(6,056,727)	(5,700,179)
Net operating real estate	17,294,140	16,849,977
Construction in Progress, Gross	787,561	989,765
Land held for development	66,769	110,142
For-sale condominium inventory	171,113	267,219
Real estate assets held for sale, net	46,438	16,678
Total real estate, net	18,366,021	18,233,781
Cash and cash equivalents	322,294	216,976
Cash in escrow	113,556	96,556
Resident security deposits	33,440	30,811
Investments in unconsolidated real estate entities	199,541	202,612
Deferred development costs	55,451	55,427
Prepaid expenses and other assets	236,348	207,715
Right of use lease assets	152,316	155,266
Total assets	19,478,967	19,199,144
LIABILITIES AND EQUITY
Unsecured notes, net	6,951,637	6,702,005
Variable rate unsecured credit facility	0	0
Mortgage notes payable, net	827,667	862,332
Dividends payable	224,760	224,897
Payables for construction	57,970	93,609
Accrued expenses and other liabilities	328,082	274,699
Lease liabilities	174,922	181,479
Accrued interest payable	62,176	49,033
Resident security deposits	59,189	55,928
Liabilities related to real estate assets held for sale	1,198	311
Total liabilities	8,687,601	8,444,293
Commitments and contingencies
Redeemable noncontrolling interests	3,136	2,677
Equity:
Preferred Stock, Value, Issued	0	0
Common Stock, Value, Issued	1,396	1,395
Additional paid-in capital	10,684,639	10,664,416
Accumulated earnings less dividends	128,549	126,022
Accumulated other comprehensive loss	(26,924)	(40,250)
Total stockholders' equity	10,787,660	10,751,583
Noncontrolling interests	570	591
Total equity	10,788,230	10,752,174
Total liabilities and equity	$ 19,478,967	$ 19,199,144

CONDENSED CONSOLIDATED BALANC_2

CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) - $ / shares	Sep. 30, 2021	Dec. 31, 2020
Statement of Financial Position [Abstract]
Preferred stock, par value (in dollars per share)	$ 0.01	$ 0.01
Preferred stock, liquidation preference (in dollars per share)	$ 25	$ 25
Preferred stock, shares authorized (in shares)	50,000,000	50,000,000
Preferred stock, shares issued (in shares)	0	0
Preferred stock, shares outstanding (in shares)	0	0
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	280,000,000	280,000,000
Common stock, shares issued (in shares)	139,638,925	139,526,671
Common stock, shares outstanding (in shares)	139,638,925	139,526,671

CONDENSED CONSOLIDATED STATEMEN

CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Revenue:
Rental and other income	$ 580,079	$ 566,387	$ 1,691,273	$ 1,742,509
Management, development and other fees	695	1,017	2,380	2,950
Total revenue	580,774	567,404	1,693,653	1,745,459
Expenses:
Operating expenses, excluding property taxes	148,704	143,909	430,377	406,991
Property taxes	72,332	68,934	212,518	202,973
Other Nonoperating Income (Expense)	417	567	1,900	4,289
Interest Expense	55,987	53,249	164,704	162,562
Loss (gain) on extinguishment of debt, net	17,890	(105)	17,768	9,333
Depreciation expense	193,791	175,348	561,560	529,508
General and administrative expense	17,313	13,985	53,130	46,878
Casualty and impairment loss	1,940	0	3,117	0
Total expenses	508,374	455,887	1,445,074	1,362,534
Income from investments in unconsolidated entities	6,867	5,083	32,959	6,770
Gains (Losses) on Sales of Investment Real Estate	58	31,607	388,354	91,338
Gain on other real estate transactions, net	1,543	129	2,002	328
Net for-sale condominium activity	158	(646)	(1,402)	4,162
Income before income taxes	81,026	147,690	670,492	485,523
Income tax (expense) benefit	(2,179)	27	(1,434)	1,069
Net income	78,847	147,717	669,058	486,592
Net loss (income) attributable to noncontrolling interests	67	(14)	32	(90)
Net income attributable to common stockholders	78,914	147,703	669,090	486,502
Other comprehensive income (loss):
Gain (loss) on cash flow hedges	2,010	1,333	1,188	(17,731)
Cash flow hedge losses reclassified to earnings	7,405	2,367	12,138	6,617
Comprehensive income	$ 88,329	$ 151,403	$ 682,416	$ 475,388
Earnings per common share - basic:
Net income attributable to common stockholders (in dollars per share)	$ 0.57	$ 1.05	$ 4.79	$ 3.46
Earnings per common share - diluted:
Net income attributable to common stockholders (in dollars per share)	$ 0.56	$ 1.05	$ 4.79	$ 3.46

CONDENSED CONSOLIDATED STATEM_2

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	1 Months Ended	3 Months Ended			9 Months Ended		12 Months Ended
	Sep. 30, 2021	Sep. 30, 2021	Mar. 31, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Cash flows from operating activities:
Net income		$ 78,847		$ 147,717	$ 669,058	$ 486,592
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation expense		193,791		175,348	561,560	529,508
Amortization of deferred financing costs					5,519	5,617
Amortization of debt discount					1,998	1,321
Loss on extinguishment of debt, net		(17,890)		105	(17,768)	(9,333)
Amortization of stock-based compensation					20,660	17,753
Equity in loss of, and return on, unconsolidated real estate entities and noncontrolling interests, net of eliminations					4,290	5,204
Real estate casualty loss					2,802	0
Abandonment of development pursuits					685	2,095
Unrealized gain on terminated cash flow hedges			$ (2,654)		(2,654)	0	$ 2,894
Cash flow hedge losses reclassified to earnings					6,874	6,617
Gain on sale of real estate assets					(413,661)	(96,823)
Gain on for-sale condominiums					(2,051)	(8,174)
Increase in resident security deposits, prepaid expenses and other assets					(20,555)	(36,332)
Increase in accrued expenses, other liabilities and accrued interest payable					59,449	39,363
Net cash provided by operating activities					911,742	962,074
Cash flows from investing activities:
Development/redevelopment of real estate assets including land acquisitions and deferred development costs					(476,307)	(562,334)
Acquisition of real estate assets, including partnership interest					(392,746)	0
Capital expenditures - existing real estate assets					(105,621)	(76,860)
Capital expenditures - non-real estate assets					(4,689)	(24,720)
Decrease in payables for construction					(35,639)	(4,095)
Proceeds from sale of real estate, net of selling costs					576,973	186,090
Proceeds from the sale of for-sale condominiums, net of selling costs					98,752	170,604
Mortgage note receivable lending					(118)	(260)
Mortgage note receivable payments					1,556	3,419
Distributions from unconsolidated real estate entities					62,157	9,877
Investments in unconsolidated real estate entities					(40,071)	(23,044)
Net cash used in investing activities					(315,753)	(321,323)
Cash flows from financing activities:
Issuance of common stock, net					7,011	1,599
Repurchase of common stock, net					0	(137,458)
Dividends paid					(666,420)	(661,000)
Issuance of mortgage notes payable					0	51,000
Repayments of mortgage notes payable, including prepayment penalties					(35,688)	(125,427)
Issuance of unsecured notes					699,167	1,296,581
Repayment of unsecured notes, including prepayment penalties					(462,147)	(958,681)
Payment of deferred financing costs					(5,281)	(11,278)
Receipt (payment) for termination of forward interest rate swaps	$ (2,211)		6,962		4,751	(25,135)
Payment to noncontrolling interest					(45)	(59)
Payments related to tax withholding for share-based compensation					(13,409)	(14,752)
Distributions to DownREIT partnership unitholders					(36)	(36)
Distributions to joint venture and profit-sharing partners					(234)	(319)
Preferred interest obligation redemption and dividends					(1,340)	(1,000)
Net cash used in financing activities					(473,671)	(585,965)
Net increase in cash, cash equivalents and cash in escrow					122,318	54,786
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Beginning Balance			$ 313,532		313,532	127,614	127,614
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Ending Balance	435,850	435,850		182,400	435,850	182,400	313,532
Cash paid during the period for interest, net of amount capitalized					127,575	133,913
Supplemental Cash Flow Information [Abstract]
Cash and cash equivalents	322,294	322,294		87,530	322,294	87,530	216,976
Cash in escrow	113,556	113,556		94,870	113,556	94,870	96,556
Cash, cash equivalents and cash in escrow reported in the Condensed Consolidated Statements of Cash Flows	$ 435,850	$ 435,850		$ 182,400	$ 435,850	$ 182,400	$ 313,532

CONDENSED CONSOLIDATED STATEM_3

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Parenthetical) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2020USD ($)Lease	Sep. 30, 2021USD ($)shares	Sep. 30, 2020USD ($)Leaseshares
Supplemental disclosures of non-cash investing and financing activities
Common stock issued through the dividend reinvestment plan (in shares) | shares		2,223	1,967
Common stock issued through the dividend reinvestment plan		$ 423	$ 339
Number of shares withheld to satisfy employees' tax withholding and other liabilities (in shares) | shares		75,542	73,103
Shares withheld to satisfy employees' tax withholding and other liabilities, value		$ 13,409	$ 14,752
Stock issued during period, shares, share-based compensation, forfeited (in shares) | shares		3,077
Stock issued during period, value, share-based compensation, forfeited		$ 595	1,187
Dividends declared but not paid		224,760
Change in redemption value of redeemable noncontrolling interest	$ 62
Increase (Decrease) in Derivative Assets		3,399	1,413
Cash flow hedge losses reclassified to earnings	2,367	12,138	$ 6,617
Operating Lease, Right-of-Use Asset		126,699
Total lease liabilities		154,790
Interest Expense
Supplemental disclosures of non-cash investing and financing activities
Cash flow hedge losses reclassified to earnings		6,874
Gain (Loss) on Extinguishment of Debt
Supplemental disclosures of non-cash investing and financing activities
Cash flow hedge losses reclassified to earnings		$ 5,264
Restricted Stock and Restricted Stock Converted From Performance Shares
Supplemental disclosures of non-cash investing and financing activities
Equity instruments granted (in shares) | shares		153,379	165,426
Performance Shares
Supplemental disclosures of non-cash investing and financing activities
Equity instruments granted (in shares) | shares		138,033
Converted to restricted stock (in shares) | shares		56,545
Restricted stock
Supplemental disclosures of non-cash investing and financing activities
Equity instruments granted (in shares) | shares		96,834	69,109
Fair value of shares issued		$ 17,187	$ 15,285
Stock issued during period, shares, share-based compensation, forfeited (in shares) | shares		3,077	7,421
Restricted Stock Converted From Performance Shares
Supplemental disclosures of non-cash investing and financing activities
Equity instruments granted (in shares) | shares		0	96,317
Common stock
Supplemental disclosures of non-cash investing and financing activities
Dividends declared but not paid	223,391	$ 223,380	$ 223,391
Accumulated earnings less dividends
Supplemental disclosures of non-cash investing and financing activities
Change in redemption value of redeemable noncontrolling interest	62	$ (789)	387
Accounting Standards Update 2016-02
Supplemental disclosures of non-cash investing and financing activities
Operating Lease, Right-of-Use Asset	46,875		46,875
Total lease liabilities	$ 46,875		$ 46,875
New Office Leases
Supplemental disclosures of non-cash investing and financing activities
Number of new office leases | Lease	2		2

Organization, Basis of Presenta

Organization, Basis of Presentation and Significant Accounting Policies	9 Months Ended
	Sep. 30, 2021
Accounting Policies [Abstract]
Organization, Basis of Presentation and Significant Accounting Policies	Organization, Basis of Presentation and Significant Accounting Policies Organization and Basis of Presentation AvalonBay Communities, Inc. (the "Company," which term, unless the context otherwise requires, refers to AvalonBay Communities, Inc. together with its subsidiaries) is a Maryland corporation that has elected to be treated as a real estate investment trust ("REIT") for federal income tax purposes under the Internal Revenue Code of 1986, as amended (the "Code"). The Company focuses on the development, redevelopment, acquisition, ownership and operation of multifamily communities in New England, the New York/New Jersey metro area, the Mid-Atlantic, the Pacific Northwest, and Northern and Southern California, as well as in the Company's expansion markets of Raleigh-Durham and Charlotte, North Carolina, Southeast Florida, Dallas and Austin, Texas, and Denver, Colorado. At September 30, 2021, the Company owned or held a direct or indirect ownership interest in 276 operating apartment communities containing 81,968 apartment homes in 13 states and the District of Columbia. In addition, the Company owned or held a direct or indirect ownership interest in 17 communities under development that are expected to contain an aggregate of 5,448 apartment homes when completed, as well as The Park Loggia, which contains 172 for-sale residential condominiums, of which 113 have been sold as of September 30, 2021, and 66,000 square feet of commercial space, of which 87% has been leased as of September 30, 2021. The Company also owned or held a direct or indirect ownership interest in land or rights to land on which the Company expects to develop an additional 22 communities that, if developed as expected, will contain an estimated 7,376 apartment homes. The interim unaudited financial statements have been prepared in accordance with U.S. generally accepted accounting principles ("GAAP") for interim financial information and in conjunction with the rules and regulations of the Securities and Exchange Commission ("SEC"). Certain information and footnote disclosures normally included in financial statements required by GAAP have been condensed or omitted pursuant to such rules and regulations. These unaudited financial statements should be read in conjunction with the financial statements and notes included in the Company's 2020 Annual Report on Form 10-K. The results of operations for the three and nine months ended September 30, 2021 are not necessarily indicative of the operating results for the full year. Management believes the disclosures are adequate to ensure the information presented is not misleading. In the opinion of management, all adjustments and eliminations, consisting only of normal, recurring adjustments necessary for a fair presentation of the financial statements for the interim periods, have been included. Capitalized terms used without definition have meanings provided elsewhere in this Form 10-Q. Earnings per Common Share Basic earnings per share is computed by dividing net income attributable to common stockholders by the weighted average number of shares outstanding during the period. All outstanding unvested restricted share awards contain rights to non-forfeitable dividends and participate in undistributed earnings with common shareholders and, accordingly, are considered participating securities that are included in the two-class method of computing basic earnings per share ("EPS"). Both the unvested restricted shares and other potentially dilutive common shares, and the related impact to earnings, are considered when calculating earnings per share on a diluted basis. The Company's earnings per common share are determined as follows (dollars in thousands, except per share data): For the three months ended For the nine months ended 9/30/2021 9/30/2020 9/30/2021 9/30/2020 Basic and diluted shares outstanding Weighted average common shares - basic 139,386,413 140,271,574 139,338,800 140,366,438 Weighted average DownREIT units outstanding 7,500 7,500 7,500 7,500 Effect of dilutive securities 343,812 324,648 298,769 328,865 Weighted average common shares - diluted 139,737,725 140,603,722 139,645,069 140,702,803 Calculation of Earnings per Share - basic Net income attributable to common stockholders $ 78,914 $ 147,703 $ 669,090 $ 486,502 Net income allocated to unvested restricted shares (160) (342) (1,443) (1,158) Net income attributable to common stockholders, adjusted $ 78,754 $ 147,361 $ 667,647 $ 485,344 Weighted average common shares - basic 139,386,413 140,271,574 139,338,800 140,366,438 Earnings per common share - basic $ 0.57 $ 1.05 $ 4.79 $ 3.46 Calculation of Earnings per Share - diluted Net income attributable to common stockholders $ 78,914 $ 147,703 $ 669,090 $ 486,502 Add: noncontrolling interests of DownREIT unitholders in consolidated partnerships 12 12 36 36 Adjusted net income attributable to common stockholders $ 78,926 $ 147,715 $ 669,126 $ 486,538 Weighted average common shares - diluted 139,737,725 140,603,722 139,645,069 140,702,803 Earnings per common share - diluted $ 0.56 $ 1.05 $ 4.79 $ 3.46 All options to purchase shares of common stock outstanding as of September 30, 2021 and 2020 are included in the computation of diluted earnings per share. Derivative Instruments and Hedging Activities The Company enters into interest rate swap and interest rate cap agreements (collectively, "Hedging Derivatives") for interest rate risk management purposes and in conjunction with certain variable rate secured debt to satisfy lender requirements. The Company does not enter into Hedging Derivative transactions for trading or other speculative purposes. The Company assesses the effectiveness of qualifying cash flow and fair value hedges, both at inception and on an on-going basis. Hedge ineffectiveness is reported as a component of interest expense, net. The fair values of Hedging Derivatives that are in an asset position are recorded in prepaid expenses and other assets. The fair value of Hedging Derivatives that are in a liability position are included in accrued expenses and other liabilities. The Company does not present or disclose the fair value of Hedging Derivatives on a net basis. Fair value changes for derivatives that are not in qualifying hedge relationships are reported as a component of interest expense, net. For the Hedging Derivative positions that the Company has determined qualify as effective cash flow hedges, the Company has recorded the cumulative changes in the fair value of Hedging Derivatives in accumulated other comprehensive loss. Amounts recorded in accumulated other comprehensive loss will be reclassified into earnings in the periods in which earnings are affected by the hedged cash flow. The effective portion of the change in fair value of the Hedging Derivatives that the Company has determined qualified as effective fair value hedges is reported as an adjustment to the carrying amount of the corresponding debt being hedged. See Note 11, “Fair Value,” for further discussion of derivative financial instruments. Legal and Other Contingencies The Company is involved in various claims and/or administrative proceedings that arise in the ordinary course of its business. While no assurances can be given, the Company does not currently believe that any of these outstanding litigation matters, individually or in the aggregate, will have a material adverse effect on its financial condition or results of operations. Acquisitions of Investments in Real Estate The Company accounts for acquisitions of investments in real estate in accordance with the authoritative guidance for the initial measurement, which first requires that the Company determine if the real estate investment is the acquisition of an asset or a business combination. Under either model, the Company must identify and determine the fair value of any assets acquired, liabilities assumed and any noncontrolling interest in the acquiree. Typical assets acquired and liabilities assumed include land, building, furniture, fixtures and equipment, debt and identified intangible assets and liabilities, consisting of the value of above or below market leases and in-place leases. In making estimates of fair values for purposes of allocating purchase price, the Company utilizes various sources, including its own analysis of recently acquired and existing comparable properties in its portfolio and other market data. Consideration for acquisitions is typically in the form of cash unless otherwise disclosed. For a business combination, the Company records the assets acquired and liabilities assumed based on the fair value of each respective item. For an asset acquisition, the allocation of the purchase price is based on the relative fair value of the net assets. The Company expenses all applicable acquisition costs for a business combination and capitalizes all applicable acquisition costs for an asset acquisition. The Company expects that acquisitions of individual operating communities will generally be viewed as asset acquisitions. Use of Estimates The preparation of financial statements in conformity with GAAP requires management to make certain estimates and assumptions. These estimates and assumptions affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the dates of the financial statements and the reported amounts of revenue and expenses during the reporting periods. Actual results could differ from those estimates. Reclassifications Certain reclassifications have been made to amounts in prior years' notes to financial statements to conform to current year presentations as a result of changes in held for sale classification, disposition activity and segment classification. For-Sale Condominium Inventory The Company presents for-sale condominium inventory at historical cost and evaluates the condominiums for impairment when potential indicators exist, as further discussed in Note 6, "Real Estate Disposition Activities." Leases The Company is party to leases as both a lessor and a lessee, primarily as follows: • lessor of residential and commercial space within its apartment communities; and • lessee under (i) ground leases for land underlying current operating or development communities and certain commercial and parking facilities and (ii) office leases for its corporate headquarters and regional offices. Lessee Considerations The Company assesses whether a contract is or contains a lease based on whether the contract conveys the right to control the use of an identified asset, including specified portions of larger assets, for a period of time in exchange for consideration. The Company’s leases include both fixed and variable lease payments, which are based on an index or rate such as the consumer price index (CPI) or percentage rents based on total sales. Lease payments included in the lease liability include only fixed lease payments including fixed amounts that depend on an index or rate. For leases that have options to extend the term or terminate the lease early, the Company only factored the impact of such options into the lease term if the option was considered reasonably certain to be exercised. The Company determined the discount rate associated with its ground and office leases on a lease by lease basis using the Company’s actual borrowing rates as well as indicative market pricing for longer term rates and taking into consideration the remaining term of each of the lease agreements. Lessor Considerations The Company evaluates leases in which it is the lessor, which are composed of residential and commercial leases at its apartment communities, and determined these leases to be operating leases. For lease agreements that provide for rent concessions and/or scheduled fixed and determinable rent increases, rental income is recognized on a straight-line basis over the noncancellable term of the lease, which, for residential leases, is generally one year. Some of the Company’s commercial leases have fixed-price renewal options, and the lessee may be able to exercise its renewal option at an amount less than the fair value of the rent at such time. The Company only includes renewal options in the lease term if, at the commencement of the lease, it is reasonably certain that the lessee will exercise this option. Additionally, for the Company’s residential and commercial leases, which are comprised of the lease component and common area maintenance as a non-lease component, the Company determined that (i) the leases are operating leases, (ii) the lease component is the predominant component and (iii) all components of its operating leases share the same timing and pattern of transfer. Revenue and Gain Recognition Revenue from contracts with customers is recognized in accordance with the transfer of goods and services to customers at an amount that reflects the consideration that the Company expects to be entitled to for those goods and services. The majority of the Company’s revenue is derived from residential and commercial rental income and other lease income, which are accounted for under ASC 842, Leases, discussed above. The Company's revenue streams that are not accounted for under ASC 842 include (i) management fees, (ii) rental and non-rental related income and (iii) gains or losses on the sale of real estate. The following table provides details of the Company’s revenue streams disaggregated by the Company’s reportable operating segments, further discussed in Note 8, “Segment Reporting,” for the three and nine months ended September 30, 2021 and 2020. Segment information for total revenue has been adjusted to exclude the real estate assets that were sold from January 1, 2020 through September 30, 2021, or otherwise qualify as held for sale as of September 30, 2021, as described in Note 6, "Real Estate Disposition Activities" (dollars in thousands): For the three months ended Same Store Other Development/ Non- Total For the period ended September 30, 2021 Management, development and other fees and other ancillary items $ — $ — $ — $ 695 $ 695 Rental and non-rental related income (2) 1,883 369 171 — 2,423 Total non-lease revenue (3) 1,883 369 171 695 3,118 Lease income (4) 517,914 27,539 28,372 — 573,825 Business interruption insurance proceeds — — — — — Total revenue $ 519,797 $ 27,908 $ 28,543 $ 695 $ 576,943 For the period ended September 30, 2020 Management, development and other fees and other ancillary items $ — $ — $ — $ 419 $ 419 Rental and non-rental related income (2) 1,965 598 112 — 2,675 Total non-lease revenue (3) 1,965 598 112 419 3,094 Lease income (4) 511,171 21,718 6,831 — 539,720 Business interruption insurance proceeds 282 — — — 282 Total revenue $ 513,418 $ 22,316 $ 6,943 $ 419 $ 543,096 For the nine months ended Same Store Other Development/ Non- Total For the period ended September 30, 2021 Management, development and other fees and other ancillary items $ — $ — $ — $ 2,380 $ 2,380 Rental and non-rental related income (2) 5,469 1,148 483 — 7,100 Total non-lease revenue (3) 5,469 1,148 483 2,380 9,480 Lease income (4) 1,514,951 75,886 65,060 — 1,655,897 Business interruption insurance proceeds — — — — — Total revenue $ 1,520,420 $ 77,034 $ 65,543 $ 2,380 $ 1,665,377 For the period ended September 30, 2020 Management, development and other fees and other ancillary items $ — $ — $ — $ 1,109 $ 1,109 Rental and non-rental related income (2) 5,447 1,637 230 — 7,314 Total non-lease revenue (3) 5,447 1,637 230 1,109 8,423 Lease income (4) 1,580,580 63,325 16,889 — 1,660,794 Business interruption insurance proceeds 378 — — — 378 Total revenue $ 1,586,405 $ 64,962 $ 17,119 $ 1,109 $ 1,669,595 __________________________________ (1) Revenue represents third-party management, asset management and developer fees and miscellaneous income and other ancillary items which are not allocated to a reportable segment. (2) Amounts include revenue streams related to leasing activities that are not considered components of a lease, including but not limited to, apartment hold fees and application fees, as well as revenue streams not related to leasing activities, including but not limited to, vendor revenue sharing, building advertising, vending and dry cleaning revenue. (3) Represents all revenue accounted for under ASC 606, Revenue from Contracts with Customers. (4) Amounts include all revenue streams derived from residential and commercial rental income and other lease income, which are accounted for under ASC 842. Due to the nature and timing of the Company’s identified revenue streams, there are no material amounts of outstanding or unsatisfied performance obligations as of September 30, 2021. Lease Revenue Reserves The Company assesses the collectability of its lease revenue and receivables on an on-going basis. Under ASC 842, Leases, the Company assesses the probability of receiving all remaining lease amounts due on a lease by lease basis, reserving for revenue and the related receivables for those leases where collection of substantially all of the remaining lease payments is not probable. Subsequently, the Company will only recognize revenue to the extent cash is received. If the Company determines that collection of the remaining lease payments becomes probable at a future date, the Company will recognize the cumulative revenue that would have been recorded under the original lease agreement. In addition to the specific reserves recognized under ASC 842, the Company also evaluates its lease receivables for collectability at a portfolio level under ASC 450, Contingencies – Loss Contingencies. The Company recognizes a reserve under ASC 450 when the uncollectible revenue is probable and reasonably estimable. The Company applies this reserve to the population of the Company’s revenue and receivables not specifically addressed as part of the specific ASC 842 reserve. COVID-19 Pandemic In March 2020, the World Health Organization designated COVID-19 as a pandemic. While the Company has taken various actions in response to the COVID-19 pandemic, the ultimate impact on its consolidated results of operations, cash flows, financial condition and liquidity will depend on, among other factors, (i) the effect on the multifamily industry and the general economy of measures taken by businesses and the government to prevent the spread of the novel coronavirus and relieve economic distress of consumers, such as governmental limitations on the ability of multifamily owners to evict residents who are delinquent in the payment of their rent and (ii) the preferences of consumers and businesses for living and working arrangements both during and after the pandemic. As of September 30, 2021, the Company assessed the collectibility of the outstanding lease income receivables as a result of the impact of the COVID-19 pandemic on its residential and commercial lease portfolios. The Company recorded an aggregate offset to income for uncollectible lease revenue for its residential and commercial portfolios of $8,586,000 and $18,755,000 for the three months ended September 30, 2021 and 2020, respectively, and $42,295,000 and $43,034,000 for the nine months ended September 30, 2021 and 2020, respectively, under ASC 842 and ASC 450.

Interest Capitalized

Interest Capitalized	9 Months Ended
	Sep. 30, 2021
Interest Capitalized
Interest Capitalized	Interest CapitalizedThe Company capitalizes interest during the development and redevelopment of real estate assets. Capitalized interest associated with the Company's development or redevelopment activities totaled $7,862,000 and $11,221,000 for the three months ended September 30, 2021 and 2020, respectively, and $25,023,000 and $33,738,000 for the nine months ended September 30, 2021 and 2020, respectively.

Mortgage Notes Payable, Unsecur

Mortgage Notes Payable, Unsecured Notes and Credit Facility	9 Months Ended
	Sep. 30, 2021
Debt Disclosure [Abstract]
Notes Payable, Unsecured Notes and Credit Facility	Mortgage Notes Payable, Unsecured Notes, Term Loans and Credit Facility The Company's mortgage notes payable, unsecured notes, variable rate unsecured term loans (the "Term Loans") and Credit Facility, as defined below, as of September 30, 2021 and December 31, 2020 are summarized below. The following amounts and discussion do not include the mortgage notes related to the communities classified as held for sale, if any, as of September 30, 2021 and December 31, 2020, as shown in the accompanying Condensed Consolidated Balance Sheets (dollars in thousands) (see Note 6, "Real Estate Disposition Activities"). 9/30/2021 12/31/2020 Fixed rate unsecured notes (1) $ 6,750,000 $ 6,500,000 Term Loans (1) 250,000 250,000 Fixed rate mortgage notes payable - conventional and tax-exempt (2) 379,636 408,964 Variable rate mortgage notes payable - conventional and tax-exempt (2) 464,650 470,850 Total mortgage notes payable and unsecured notes and Term Loans 7,844,286 7,629,814 Credit Facility — — Total mortgage notes payable, unsecured notes, Term Loans and Credit Facility $ 7,844,286 $ 7,629,814 _____________________________________ (1) Balances at September 30, 2021 and December 31, 2020 exclude $9,915 and $10,380, respectively, of debt discount, and $38,448 and $37,615, respectively, of deferred financing costs, as reflected in unsecured notes, net on the accompanying Condensed Consolidated Balance Sheets. (2) Balances at September 30, 2021 and December 31, 2020 exclude $13,806 and $14,478, respectively, of debt discount, and $2,813 and $3,004, respectively, of deferred financing costs, as reflected in mortgage notes payable, net on the accompanying Condensed Consolidated Balance Sheets. The following debt activity occurred during the nine months ended September 30, 2021: • In January 2021, the Company repaid $27,795,000 principal amount of 5.37% fixed rate debt secured by Avalon San Bruno II at par in advance of its April 2021 maturity date. • In September 2021, the Company repaid $450,000,000 principal amount of its 2.95% unsecured notes in advance of the September 2022 scheduled maturity, recognizing a loss on debt extinguishment of $17,890,000, composed of a prepayment penalty of $12,147,000, and the non-cash write off of unamortized deferred hedging losses and unamortized deferred financing costs of $5,743,000. • In September 2021, the Company issued $700,000,000 principal amount of unsecured notes in a public offering under its existing shelf registration statement for proceeds net of underwriting fees of approximately $694,617,000, before considering the impact of other offering costs. The notes mature in January 2032 and were issued at a 2.050% interest rate. The notes were issued under the Company's green bond framework, and the Company has allocated or will allocate the net proceeds, in whole or in part, to one or more new or existing eligible green projects. At September 30, 2021, the Company had a $1,750,000,000 revolving variable rate unsecured credit facility with a syndicate of banks (the “Credit Facility”) which matures in February 2024. The Credit Facility bears interest at varying levels based on (i) the London Interbank Offered Rate (“LIBOR”) applicable to the period of borrowing for a particular draw of funds from the facility (e.g., one month to maturity, three months to maturity, etc.) and (ii) the rating levels issued for our unsecured notes. The current stated pricing for drawn borrowings is LIBOR plus 0.775% per annum (0.86% at September 30, 2021), assuming a one month borrowing rate. The annual facility fee for the Credit Facility remained 0.125%, resulting in a fee of $2,188,000 annually based on the $1,750,000,000 facility size and based on the Company's current credit rating. The Company had no borrowings outstanding under the Credit Facility and had $2,599,000 and $2,900,000 outstanding in letters of credit that reduced the borrowing capacity as of September 30, 2021 and December 31, 2020, respectively. In addition, the Company had $37,596,000 and $32,079,000 outstanding in additional letters of credit unrelated to the Credit Facility as of September 30, 2021 and December 31, 2020, respectively. In the aggregate, secured notes payable mature at various dates from March 2027 through July 2066, and are secured by certain apartment communities (with a net carrying value of $1,365,559,000, excluding communities classified as held for sale, as of September 30, 2021). The weighted average interest rate of the Company's fixed rate secured notes payable (conventional and tax-exempt) was 3.8% at both September 30, 2021 and December 31, 2020. The weighted average interest rate of the Company's variable rate secured notes payable (conventional and tax-exempt), including the effect of certain financing related fees, was 1.6% and 1.7% at September 30, 2021 and December 31, 2020, respectively. Scheduled payments and maturities of secured notes payable and unsecured notes outstanding at September 30, 2021 are as follows (dollars in thousands): Year Secured notes Secured notes maturities Unsecured notes and Term Loans maturities Stated interest rate of unsecured notes and Term Loans 2021 $ 1,460 $ — $ — N/A 2022 9,918 — — N/A 100,000 LIBOR + 0.90% 2023 10,739 — 350,000 4.200 % 250,000 2.850 % 2024 11,677 — 300,000 3.500 % 150,000 LIBOR + 0.85% 2025 12,408 — 525,000 3.450 % 300,000 3.500 % 2026 13,445 — 475,000 2.950 % 300,000 2.900 % 2027 15,880 236,100 400,000 3.350 % 2028 20,707 — 450,000 3.200 % 2029 11,742 66,250 450,000 3.300 % 2030 12,384 — 700,000 2.300 % Thereafter 176,078 245,498 600,000 2.450 % 700,000 2.050 % 350,000 3.900 % 300,000 4.150 % 300,000 4.350 % $ 296,438 $ 547,848 $ 7,000,000

Equity

Equity	9 Months Ended
	Sep. 30, 2021
Stockholders' Equity Note [Abstract]
Equity	Equity The following summarizes the changes in equity for the nine months ended September 30, 2021 (dollars in thousands): Common Additional Accumulated Accumulated Total stockholder's equity Noncontrolling interests Total Balance at December 31, 2020 $ 1,395 $ 10,664,416 $ 126,022 $ (40,250) $ 10,751,583 $ 591 $ 10,752,174 Net income attributable to common stockholders — — 142,223 — 142,223 — 142,223 Cash flow hedge losses reclassified to earnings — — — 2,367 2,367 — 2,367 Change in redemption value of redeemable noncontrolling interest — — (273) — (273) — (273) Noncontrolling interest distribution and income allocation — — — — — (16) (16) Dividends declared to common stockholders ($1.59 per share) — — (221,779) — (221,779) — (221,779) Issuance of common stock, net of withholdings 1 (14,037) 958 — (13,078) — (13,078) Amortization of deferred compensation — 7,286 — — 7,286 — 7,286 Balance at March 31, 2021 $ 1,396 $ 10,657,665 $ 47,151 $ (37,883) $ 10,668,329 $ 575 $ 10,668,904 Net income attributable to common stockholders — — 447,953 — 447,953 — 447,953 Loss on cash flow hedges, net — — — (822) (822) — (822) Cash flow hedge losses reclassified to earnings — — — 2,366 2,366 — 2,366 Change in redemption value of redeemable noncontrolling interest — — (255) — (255) — (255) Noncontrolling interest distribution and income allocation — — — — — (7) (7) Dividends declared to common stockholders ($1.59 per share) — — (222,451) — (222,451) — (222,451) Issuance of common stock, net of withholdings — 2,496 — — 2,496 — 2,496 Amortization of deferred compensation — 10,403 — — 10,403 — 10,403 Balance at June 30, 2021 $ 1,396 $ 10,670,564 $ 272,398 $ (36,339) $ 10,908,019 $ 568 $ 10,908,587 Net income attributable to common stockholders — — 78,914 — 78,914 — 78,914 Gain on cash flow hedges, net — — — 2,010 2,010 — 2,010 Cash flow hedge losses reclassified to earnings — — — 7,405 7,405 — 7,405 Change in redemption value of redeemable noncontrolling interest — — (261) — (261) — (261) Noncontrolling interest distribution and income allocation — — — — — 2 2 Dividends declared to common stockholders ($1.59 per share) — — (222,475) — (222,475) — (222,475) Issuance of common stock, net of withholdings — 4,633 (27) — 4,606 — 4,606 Amortization of deferred compensation — 9,442 — — 9,442 — 9,442 Balance at September 30, 2021 $ 1,396 $ 10,684,639 $ 128,549 $ (26,924) $ 10,787,660 $ 570 $ 10,788,230 The following summarizes the changes in equity for the nine months ended September 30, 2020 (dollars in thousands): Common Additional Accumulated Accumulated Total stockholder's equity Noncontrolling interests Total Balance at December 31, 2019 $ 1,406 $ 10,736,733 $ 282,913 $ (31,503) $ 10,989,549 $ 649 $ 10,990,198 Net income attributable to common stockholders — — 167,971 — 167,971 — 167,971 Loss on cash flow hedges, net — — — (17,603) (17,603) — (17,603) Cash flow hedge losses reclassified to earnings — — — 1,949 1,949 — 1,949 Change in redemption value of redeemable noncontrolling interest — — 471 — 471 — 471 Noncontrolling interests income allocation — — — — — (35) (35) Dividends declared to common stockholders ($1.59 per share) — — (224,083) — (224,083) — (224,083) Issuance of common stock, net of withholdings 1 (12,492) (1,616) — (14,107) — (14,107) Amortization of deferred compensation — 7,781 — — 7,781 — 7,781 Balance at March 31, 2020 $ 1,407 $ 10,732,022 $ 225,656 $ (47,157) $ 10,911,928 $ 614 $ 10,912,542 Net income attributable to common stockholders — — 170,828 — 170,828 — 170,828 Loss on cash flow hedges, net — — — (1,461) (1,461) — (1,461) Cash flow hedge losses reclassified to earnings — — — 2,301 2,301 — 2,301 Change in redemption value of redeemable noncontrolling interest — — (146) — (146) — (146) Noncontrolling interests income allocation — — — — — 1 1 Dividends declared to common stockholders ($1.59 per share) — — (224,172) — (224,172) — (224,172) Issuance of common stock, net of withholdings — 1,050 138 — 1,188 — 1,188 Amortization of deferred compensation — 9,724 — — 9,724 — 9,724 Balance at June 30, 2020 $ 1,407 $ 10,742,796 $ 172,304 $ (46,317) $ 10,870,190 $ 615 $ 10,870,805 Net income attributable to common stockholders — — 147,703 — 147,703 — 147,703 Gain on cash flow hedges, net — — — 1,333 1,333 — 1,333 Cash flow hedge losses reclassified to earnings — — — 2,367 2,367 — 2,367 Change in redemption value of redeemable noncontrolling interest — — 62 — 62 — 62 Noncontrolling interest distribution and income allocation — — — — — (17) (17) Dividends declared to common stockholders ($1.59 per share) — — (222,694) — (222,694) — (222,694) Issuance of common stock, net of withholdings — 105 — — 105 — 105 Repurchase of common stock, including repurchase costs (9) (69,779) (67,670) — (137,458) — (137,458) Amortization of deferred compensation — 8,036 — — 8,036 — 8,036 Balance at September 30, 2020 $ 1,398 $ 10,681,158 $ 29,705 $ (42,617) $ 10,669,644 $ 598 $ 10,670,242 As of September 30, 2021 and December 31, 2020, the Company's charter had authorized for issuance a total of 280,000,000 shares of common stock and 50,000,000 shares of preferred stock. During the nine months ended September 30, 2021, the Company: i. issued 2,126 shares of common stock in connection with stock options exercised; ii. issued 2,223 shares of common stock through the Company's dividend reinvestment plan; iii. issued 153,379 shares of common stock in connection with restricted stock grants and the conversion of performance awards to shares of common stock; iv. sold 21,000 shares of common stock under CEP V, as discussed below; v. withheld 75,542 shares of common stock to satisfy employees' tax withholding and other liabilities; vi. issued 12,145 shares of common stock through the Employee Stock Purchase Plan; and vii. canceled 3,077 shares of restricted common stock upon forfeiture. Any deferred compensation related to the Company's stock option, restricted stock and performance award grants as of September 30, 2021 is not reflected on the accompanying Condensed Consolidated Balance Sheets as of September 30, 2021, and will not be reflected until recognized as compensation cost. In July 2020, the Company’s Board of Directors voted to terminate the Company’s prior $500,000,000 Stock Repurchase Program (the "Amended 2005 Stock Repurchase Program") and approved a new stock repurchase program under which the Company may acquire shares of its common stock in open market or negotiated transactions up to an aggregate purchase price of $500,000,000 (the "2020 Stock Repurchase Program"). Purchases of common stock under the 2020 Stock Repurchase Program may be exercised from time to time in the Company’s discretion and in such amounts as market conditions warrant. The timing and actual number of shares repurchased will depend on a variety of factors, including price, corporate and regulatory requirements, market conditions and other corporate liquidity requirements and priorities. The 2020 Stock Repurchase Program does not have an expiration date and may be suspended or terminated at any time without prior notice. During the nine months ended September 30, 2021, the Company had no repurchases of shares under this program. As of September 30, 2021, the Company had $316,148,000 remaining authorized for purchase under this program. In May 2019, the Company commenced a fifth continuous equity program ("CEP V") under which the Company may sell (and/or enter into forward sale agreements for the sale of) up to $1,000,000,000 of its common stock from time to time. Actual sales will depend on a variety of factors to be determined by the Company, including market conditions, the trading price of the Company's common stock and determinations by the Company of the appropriate sources of funding for the Company. In conjunction with CEP V, the Company engaged sales agents who will receive compensation of up to 1.5% of the gross sales price for shares sold. The Company expects that, if entered into, it will physically settle each forward sale agreement on one or more dates specified by the Company on or prior to the maturity date of that particular forward sale agreement, in which case the Company will expect to receive aggregate net cash proceeds at settlement equal to the number of shares underlying the particular forward agreement multiplied by the relevant forward sale price. However, the Company may also elect to cash settle or net share settle a forward sale agreement. In connection with each forward sale agreement, the Company will pay the relevant forward seller, in the form of a reduced initial forward sale price, a commission of up to 1.5% of the sales prices of all borrowed shares of common stock sold. During the three and nine months ended September 30, 2021, the Company sold 21,000 shares of common stock at an average sales price of $227.60 per share, for net proceeds of $4,708,000 under the program. As of September 30, 2021, the Company had $748,099,000 remaining authorized for issuance under CEP V.

Investments in Real Estate Enti

Investments in Real Estate Entities	9 Months Ended
	Sep. 30, 2021
Equity Method Investments and Joint Ventures [Abstract]
Investments in Real Estate Entities	Investments in Real Estate Entities Investments in Unconsolidated Real Estate Entities As of September 30, 2021, the Company had investments in eight unconsolidated real estate entities with ownership interest percentages ranging from 20.0% to 50.0% and other unconsolidated investments. The Company accounts for its investments in unconsolidated real estate entities under the equity method of accounting or under the measurement alternative with the carrying amount of the investment adjusted to fair value when there is an observable transaction for the same or similar investment of the same issuer indicating a change in fair value. The significant accounting policies of the Company's unconsolidated real estate entities are consistent with those of the Company in all material respects. During the nine months ended September 30, 2021, Archstone Multifamily Partners AC JV LP (the "AC JV") sold its final two communities, Avalon North Point and Avalon North Point Lofts, located in Cambridge, MA, containing an aggregate of 529 apartment homes, for $325,000,000. The Company's share of the gain was $23,305,000. In conjunction with the disposition of Avalon North Point, the AC JV repaid a $111,653,000 loan to the equity investors in the venture at par. The following is a combined summary of the financial position of the entities accounted for using the equity method or the measurement alternative discussed above as of the dates presented, including development joint ventures started and unconsolidated communities sold during the respective periods (dollars in thousands): 9/30/2021 12/31/2020 (unaudited) Assets: Real estate, net $ 1,171,955 $ 1,249,730 Other assets 326,339 255,606 Total assets $ 1,498,294 $ 1,505,336 Liabilities and partners' capital: Mortgage notes payable, net (1) $ 636,796 $ 751,257 Other liabilities 172,660 163,808 Partners' capital 688,838 590,271 Total liabilities and partners' capital $ 1,498,294 $ 1,505,336 _________________________________ (1) Includes the variable rate construction loan secured by AVA Arts District, of which $1,032,000 has been drawn as of September 30, 2021 . The Company has guaranteed the construction loan on behalf of the venture, and any obligations the Company may incur under the guarantee, except for those due to misconduct by the Company, are required capital contributions of the partners based on ownership interest. The Company has not guaranteed any other outstanding debt, nor does the Company have any obligation to fund this debt should the unconsolidated entity be unable to do so. The following is a combined summary of the operating results of the entities accounted for using the equity method discussed above for the periods presented (dollars in thousands): For the three months ended For the nine months ended 9/30/2021 9/30/2020 9/30/2021 9/30/2020 (unaudited) (unaudited) Rental and other income (1) $ 44,819 $ 28,800 $ 111,562 $ 92,299 Operating and other expenses (10,698) (12,782) (34,992) (37,034) Gain on sale of communities — 18,408 164,317 18,448 Interest expense, net (6,137) (8,024) (21,386) (24,133) Depreciation expense (6,912) (8,704) (22,831) (26,106) Net income $ 21,072 $ 17,698 $ 196,670 $ 23,474 Company's share of net income from investments in unconsolidated entities $ 7,287 $ 5,611 $ 34,435 $ 8,357 Amortization of excess investment and other (420) (528) (1,476) (1,587) Income from investments in unconsolidated entities $ 6,867 $ 5,083 $ 32,959 $ 6,770 _________________________________ (1) Includes unrealized gains on property technology investments during the three and nine months ended September 30, 2021. Investments in Consolidated Real Estate Entities During the nine months ended September 30, 2021, the Company acquired four consolidated communities: • Avalon Arundel Crossing East, located in Linthicum Heights, MD, which contains 384 apartment homes and was acquired for a purchase price of $119,000,000. • The Nexus Lakeside, located in Flower Mound, TX, which contains 425 apartment homes and 18,000 square feet of commercial space and was acquired for a purchase price of $117,000,000. • Hub South End, located in Charlotte, NC, which contains 265 apartment homes and 23,000 square feet of commercial space and was acquired for a purchase price of $104,350,000. • Three30Five, located in Charlotte, NC, which contains 164 apartment homes and was acquired for a purchase price of $52,650,000. The Company accounted for these purchases as asset acquisitions and recorded the acquired assets and assumed liabilities, including identifiable intangibles, at their relative fair values based on the purchase price and acquisition costs incurred. The Company used third party pricing or internal models for the value of the land, a valuation model for the value of the building, and an internal model to determine the fair value of the remaining real estate assets and in-place leases. Given the heterogeneous nature of multifamily real estate, the fair values for the land, debt, real estate assets and in-place leases incorporated significant unobservable inputs and therefore are considered to be Level 3 prices within the fair value hierarchy. Expensed Transaction, Development and Other Pursuit Costs The Company capitalizes pre-development costs incurred in pursuit of new development opportunities for which the Company currently believes future development is probable ("Development Rights"). Future development of these Development Rights is dependent upon various factors, including zoning and regulatory approval, rental market conditions, construction costs and the availability of capital. Initial pre-development costs incurred for pursuits for which future development is not yet considered probable are expensed as incurred. In addition, if the status of a Development Right changes, making future development by the Company no longer probable, any non-recoverable capitalized pre-development costs are expensed. The Company expensed costs related to development pursuits not yet considered probable for development and the abandonment of Development Rights, as well as costs incurred in pursuing the acquisition or disposition of assets for which such acquisition and disposition activity did not occur. The amounts for the three and nine months ended September 30, 2021 and 2020, were $417,000 and $1,900,000 and $567,000 and $4,289,000, respectively. These costs are included in expensed transaction, development and other pursuit costs, net of recoveries on the accompanying Condensed Consolidated Statements of Comprehensive Income. Abandoned pursuit costs can vary greatly, and the costs incurred in any given period may be significantly different in future periods. Casualty and Impairment of Long-Lived Assets In the Company's evaluation of its real estate portfolio for impairment, as discussed below, it considered the impact of the COVID-19 pandemic and did not identify any indicators of impairment as a result. The Company evaluates its real estate and other long-lived assets for impairment when potential indicators of impairment exist. Such assets are stated at cost, less accumulated depreciation and amortization, unless the carrying amount of the asset is not recoverable. If events or circumstances indicate that the carrying amount of a property or long-lived asset may not be recoverable, the Company assesses its recoverability by comparing the carrying amount of the property or long-lived asset to its estimated undiscounted future cash flows. If the carrying amount exceeds the aggregate undiscounted future cash flows, the Company recognizes an impairment loss to the extent the carrying amount exceeds the estimated fair value of the property or long-lived asset. Based on periodic tests of recoverability of long-lived assets, the Company did not recognize any impairment losses for the three and nine months ended September 30, 2021 and 2020, other than those related to casualty losses from property damage. During the three and nine months ended September 30, 2021, the Company recognized a charge of $1,971,000 for the property and casualty damages across several communities in its East Coast markets related to severe storms, reported as casualty and impairment loss on the accompanying Condensed Consolidated Statements of Comprehensive Income. In addition, during the nine months ended September 30, 2021, the Company recognized a charge of $1,146,000 for the property and casualty damages resulting from a fire at an operating community, reported as casualty and impairment loss on the accompanying Condensed Consolidated Statements of Comprehensive Income. The Company evaluates its for-sale condominium inventory for potential indicators of impairment, considering whether the fair value of the individual for-sale condominium units exceeds the carrying value of those units. For-sale condominium inventory is stated at cost, unless the carrying amount of the inventory is not recoverable when compared to the fair value of each unit. The Company determines the fair value of its for-sale condominium inventory as the estimated sales price less direct costs to sell. For the three and nine months ended September 30, 2021 and 2020, the Company did not recognize any impairment losses on its for-sale condominium inventory. The Company assesses its portfolio of land held for both development and investment for impairment if the intent of the Company changes with respect to either the development of, or the expected holding period for, the land. During the three and nine months ended September 30, 2021 and 2020, the Company did not recognize any impairment charges on its investment in land. The Company evaluates its unconsolidated investments for other than temporary impairment, considering both the extent and amount by which the carrying value of the investment exceeds the fair value, and the Company's intent and ability to hold the investment to recover its carrying value. The Company also evaluates its proportionate share of any impairment of assets held by unconsolidated investments. There were no other than temporary impairment losses recognized for any of the Company's investments in unconsolidated real estate entities during the three and nine months ended September 30, 2021 and 2020.

Real Estate Disposition Activit

Real Estate Disposition Activities	9 Months Ended
	Sep. 30, 2021
Discontinued Operations and Disposal Groups [Abstract]
Real Estate Disposition Activities	Real Estate Disposition Activities The following real estate sales occurred during the nine months ended September 30, 2021: Community name Location Period of sale Apartment homes Gross sales price Gain on eaves Stamford Stamford, CT Q121 238 $ 72,000 $ 53,775 Avalon Norwalk Norwalk, CT Q221 311 $ 103,000 $ 48,912 AVA Cortez Hill San Diego, CA Q221 299 $ 96,500 $ 75,716 Avalon Redmond Place Redmond, WA Q221 222 $ 97,700 $ 72,929 Avalon Bronxville Bronxville, NY Q221 110 $ 89,000 $ 71,773 Avalon Glen Cove & Avalon Glen Cove North Glen Cove, NY Q221 367 $ 126,000 $ 65,242 _________________________________ (1) Gain on disposition was reported in gain on sale of communities on the accompanying Condensed Consolidated Statements of Comprehensive Income. At September 30, 2021, the Company had one real estate asset that qualified as held for sale. The Park Loggia The Park Loggia, located in New York, NY, contains 172 for-sale residential condominiums and 66,000 square feet of commercial space. During the three and nine months ended September 30, 2021, the Company sold 17 and 43 residential condominiums at The Park Loggia, for gross proceeds of $54,277,000 and $107,278,000, respectively, resulting in a gain in accordance with GAAP of $1,345,000 and $2,051,000, respectively. As of September 30, 2021, the Company had sold 113 residential condominiums and there were 59 residential condominiums remaining to be sold. The Company incurred $1,187,000 and $1,373,000 during the three months ended September 30, 2021 and 2020, respectively, and $3,453,000 and $4,012,000 during the nine months ended September 30, 2021 and 2020, respectively, in marketing, operating and administrative costs. All amounts are included in net for-sale condominium activity, on the accompanying Condensed Consolidated Statements of Comprehensive Income. As of September 30, 2021 and December 31, 2020, the unsold for-sale residential condominiums at The Park Loggia had an aggregate carrying value of $171,113,000 and $267,219,000, respectively, presented as for-sale condominium inventory on the accompanying Condensed Consolidated Balance Sheets.

Commitments and Contingencies

Commitments and Contingencies	9 Months Ended
	Sep. 30, 2021
Leases [Abstract]
Commitments and Contingencies	Commitments and Contingencies Lease Obligations The Company owns eight apartment communities and two commercial properties, located on land subject to ground leases expiring between July 2046 and March 2142. The Company has purchase options for all ground leases expiring prior to 2060. The ground leases for seven of the eight apartment communities and the rest of the ground leases are operating leases, with rental expense recognized on a straight-line basis over the lease term. In addition, the Company is party to 13 leases for its corporate and regional offices with varying terms through 2031, all of which are operating leases. During the three and nine months ended September 30, 2021, the Company exercised its purchase option under an operating lease, acquiring the land encumbered by the ground lease for Avalon Hackensack at Riverside for $10,336,000. As of September 30, 2021 and December 31, 2020, the Company had total operating lease assets of $126,699,000 and $133,581,000, respectively, and lease obligations of $154,790,000 and $161,313,000, respectively, reported as components of right of use lease assets and lease liabilities, respectively, on the accompanying Condensed Consolidated Balance Sheets. The Company incurred costs of $3,905,000 and $3,958,000 for the three months ended September 30, 2021 and 2020, respectively, and $11,628,000 and $12,115,000 for the nine months ended September 30, 2021 and 2020, respectively, related to operating leases.
Commitments and Contingencies	Commitments and Contingencies Lease Obligations The Company owns eight apartment communities and two commercial properties, located on land subject to ground leases expiring between July 2046 and March 2142. The Company has purchase options for all ground leases expiring prior to 2060. The ground leases for seven of the eight apartment communities and the rest of the ground leases are operating leases, with rental expense recognized on a straight-line basis over the lease term. In addition, the Company is party to 13 leases for its corporate and regional offices with varying terms through 2031, all of which are operating leases. During the three and nine months ended September 30, 2021, the Company exercised its purchase option under an operating lease, acquiring the land encumbered by the ground lease for Avalon Hackensack at Riverside for $10,336,000. As of September 30, 2021 and December 31, 2020, the Company had total operating lease assets of $126,699,000 and $133,581,000, respectively, and lease obligations of $154,790,000 and $161,313,000, respectively, reported as components of right of use lease assets and lease liabilities, respectively, on the accompanying Condensed Consolidated Balance Sheets. The Company incurred costs of $3,905,000 and $3,958,000 for the three months ended September 30, 2021 and 2020, respectively, and $11,628,000 and $12,115,000 for the nine months ended September 30, 2021 and 2020, respectively, related to operating leases.

Segment Reporting

Segment Reporting	9 Months Ended
	Sep. 30, 2021
Segment Reporting [Abstract]
Segment Reporting	Segment Reporting The Company's reportable operating segments include Same Store, Other Stabilized, and Development/Redevelopment. Annually as of January 1, the Company determines which of its communities fall into each of these categories and generally maintains that classification throughout the year for the purpose of reporting segment operations, unless disposition or redevelopment plans regarding a community change. In addition, the Company owns land for future development and has other corporate assets that are not allocated to an operating segment. The Company's segment disclosures present the measure(s) used by the chief operating decision maker ("CODM") for purposes of assessing each segment's performance. The Company's CODM is comprised of several members of its executive management team who use net operating income ("NOI") as the primary financial measure for Same Store communities and Other Stabilized communities. NOI is defined by the Company as total property revenue less direct property operating expenses (including property taxes), and excluding corporate-level income (including management, development and other fees), corporate-level property management and other indirect operating expenses, expensed transaction, development and other pursuit costs, net of recoveries, interest expense, net, loss (gain) on extinguishment of debt, net, general and administrative expense, income from investments in unconsolidated entities, depreciation expense, corporate income tax expense (benefit), casualty and impairment loss, gain on sale of communities, gain on other real estate transactions, net, net for-sale condominium activity and net operating income from real estate assets sold or held for sale. The CODM evaluates the Company's financial performance on a consolidated residential and commercial basis, as the Company's commercial results attributable to the non-apartment components of the Company's mixed-use communities and other nonresidential operations represents 1.8% and 1.2% of total NOI for the three months ended September 30, 2021 and 2020, respectively, and 1.6% and 1.1% for the nine months ended September 30, 2021 and 2020, respectively. Although the Company considers NOI a useful measure of a community's or communities' operating performance, NOI should not be considered an alternative to net income or net cash flow from operating activities, as determined in accordance with GAAP. NOI excludes a number of income and expense categories as detailed in the reconciliation of NOI to net income. A reconciliation of NOI to net income for the three and nine months ended September 30, 2021 and 2020 is as follows (dollars in thousands): For the three months ended For the nine months ended 9/30/2021 9/30/2020 9/30/2021 9/30/2020 Net income $ 78,847 $ 147,717 $ 669,058 $ 486,592 Property management and other indirect operating expenses, net of corporate income 25,322 23,837 74,110 70,043 Expensed transaction, development and other pursuit costs, net of recoveries 417 567 1,900 4,289 Interest expense, net 55,987 53,249 164,704 162,562 Loss (gain) on extinguishment of debt, net 17,890 (105) 17,768 9,333 General and administrative expense 17,313 13,985 53,130 46,878 Income from investments in unconsolidated entities (6,867) (5,083) (32,959) (6,770) Depreciation expense 193,791 175,348 561,560 529,508 Income tax expense (benefit) 2,179 (27) 1,434 (1,069) Casualty and impairment loss 1,940 — 3,117 — Gain on sale of communities (58) (31,607) (388,354) (91,338) Gain on other real estate transactions, net (1,543) (129) (2,002) (328) Net for-sale condominium activity (158) 646 1,402 (4,162) Net operating income from real estate assets sold or held for sale (2,373) (14,686) (17,393) (47,798) Net operating income $ 382,687 $ 363,712 $ 1,107,475 $ 1,157,740 The following is a summary of NOI from real estate assets sold or held for sale for the periods presented (dollars in thousands): For the three months ended For the nine months ended 9/30/2021 9/30/2020 9/30/2021 9/30/2020 Rental income from real estate assets sold or held for sale $ 3,831 $ 24,308 $ 28,276 $ 75,864 Operating expenses from real estate assets sold or held for sale (1,458) (9,622) (10,883) (28,066) Net operating income from real estate assets sold or held for sale $ 2,373 $ 14,686 $ 17,393 $ 47,798 The primary performance measure for communities under development or redevelopment depends on the stage of completion. While under development, management monitors actual construction costs against budgeted costs as well as lease-up pace and rent levels compared to budget. The following table provides details of the Company's segment information as of the dates specified (dollars in thousands). The segments are classified based on the individual community's status at January 1, 2021. Segment information for the three and nine months ended September 30, 2021 and 2020 has been adjusted to exclude the real estate assets that were sold from January 1, 2020 through September 30, 2021, or otherwise qualify as held for sale as of September 30, 2021, as described in Note 6, "Real Estate Disposition Activities." For the three months ended For the nine months ended Total NOI Total NOI Gross real estate (1) For the period ended September 30, 2021 Same Store New England $ 77,037 $ 48,115 $ 224,614 $ 142,278 $ 2,781,806 Metro NY/NJ 108,776 72,564 319,079 215,147 4,129,121 Mid-Atlantic 85,328 56,103 252,271 168,359 3,575,978 Southeast Florida 8,152 5,026 23,099 13,772 395,594 Denver, CO 6,070 4,011 17,576 11,965 320,214 Pacific Northwest 28,092 19,197 81,640 55,389 1,057,166 Northern California 90,127 63,088 270,124 190,658 3,458,280 Southern California 116,215 79,590 332,017 225,489 4,382,656 Total Same Store 519,797 347,694 1,520,420 1,023,057 20,100,815 Other Stabilized 27,908 18,217 77,034 49,796 1,528,196 Development / Redevelopment 28,543 16,776 65,543 34,622 2,401,751 Land Held for Development N/A N/A N/A N/A 66,769 Non-allocated (2) 695 N/A 2,380 N/A 278,779 Total $ 576,943 $ 382,687 $ 1,665,377 $ 1,107,475 $ 24,376,310 For the period ended September 30, 2020 Same Store New England $ 75,394 $ 48,290 $ 231,478 $ 152,589 $ 2,756,835 Metro NY/NJ 106,542 72,283 325,807 225,793 4,102,402 Mid-Atlantic 84,974 56,721 261,932 182,503 3,550,373 Southeast Florida 6,950 3,331 21,818 11,755 393,594 Denver, CO 5,422 3,418 15,758 10,084 319,038 Pacific Northwest 27,545 18,913 84,808 59,977 1,051,451 Northern California 97,777 71,207 308,522 232,470 3,430,831 Southern California 108,814 72,995 336,282 233,666 4,349,770 Total Same Store 513,418 347,158 1,586,405 1,108,837 19,954,294 Other Stabilized 22,316 14,238 64,962 42,251 1,125,829 Development / Redevelopment 6,943 2,316 17,119 6,652 1,698,823 Land Held for Development N/A N/A N/A N/A 43,494 Non-allocated (2) 419 N/A 1,109 N/A 399,048 Total $ 543,096 $ 363,712 $ 1,669,595 $ 1,157,740 $ 23,221,488 __________________________________ (1) Does not include gross real estate assets held for sale of $89,529 as of September 30, 2021 and gross real estate assets either sold or classified as held for sale subsequent to September 30, 2020 of $720,432. (2) Revenue represents third-party management, accounting, and developer fees and miscellaneous income and other ancillary items which are not allocated to a reportable segment. Gross real estate includes the for-sale residential condominiums at The Park Loggia, as discussed in Note 6, "Real Estate Disposition Activities."

Stock-Based Compensation Plans

Stock-Based Compensation Plans	9 Months Ended
	Sep. 30, 2021
Share-based Payment Arrangement [Abstract]
Stock-Based Compensation Plans	Stock-Based Compensation Plans As part of its long-term compensation plans, the Company has granted stock options, performance awards and restricted stock. Details of the outstanding awards and activity are presented below. Information with respect to stock options granted under the Company's Second Amended and Restated 2009 Equity Incentive Plan (the "2009 Plan") for the three and nine months ended September 30, 2021, is as follows: 2009 Plan Weighted average Options Outstanding, December 31, 2020 12,506 $ 129.35 Exercised (2,126) 121.78 Granted (1) 294,115 180.32 Forfeited (4,713) 180.32 Options Outstanding, September 30, 2021 299,782 $ 178.61 Options Exercisable, September 30, 2021 10,380 $ 130.90 __________________________________ (1) Includes 4,847 options resulting from recipient elections to receive a portion of earned restricted stock awards in the form of stock options. The Company granted stock options in 2021 with the exercise price equal to the closing stock price on the date of grant. The stock options awarded in 2021 will cliff vest in two years on March 1, 2023 and they have a ten-year term. The Company used the Black-Scholes Option Pricing model to determine the grant date fair value of options. The assumptions used are as follows: 2021 Dividend yield 3.5% Estimated volatility 27.1% Risk free rate 0.81% Expected life of options 5 years Estimated fair value $28.64 Information with respect to performance awards granted is as follows: Performance awards Weighted average grant date fair value per award Outstanding at December 31, 2020 241,921 $ 195.13 Granted (1) 138,033 191.12 Change in awards based on performance (2) (37,469) 156.00 Converted to shares of common stock (56,545) 156.00 Forfeited (1,418) 207.65 Outstanding at September 30, 2021 284,522 $ 206.05 __________________________________ (1) The amount of shares of common stock that ultimately may be earned is based on the total shareholder return metrics related to the Company's common stock for 69,064 performance awards and financial metrics related to operating performance, net asset value and leverage metrics of the Company for 68,969 performance awards. (2) Represents the change in the number of performance awards earned based on performance achievement for the performance period. The Company used a Monte Carlo model to assess the compensation cost associated with the portion of the performance awards granted in 2021 for which achievement will be determined by using total shareholder return measures. The assumptions used are as follows: 2021 Dividend yield 3.5% Estimated volatility over the life of the plan (1) 22.0% - 49.0% Risk free rate 0.06% - 0.38% Estimated performance award value based on total shareholder return measure $213.16 __________________________________ (1) Estimated volatility over the life of the plan is using 50% historical volatility and 50% implied volatility. For the portion of the performance awards granted in 2021 for which achievement will be determined by using financial metrics, the compensation cost was based on a weighted average grant date value of $178.38, and the Company's estimate of corporate achievement for the financial metrics. Information with respect to restricted stock granted is as follows: Restricted stock shares Restricted stock shares weighted average grant date fair value per share Restricted stock shares converted from performance awards Outstanding at December 31, 2020 131,724 $ 203.28 146,319 Granted - restricted stock shares 96,834 177.49 — Vested - restricted stock shares (68,702) 192.07 (71,692) Forfeited (3,077) 193.47 — Outstanding at September 30, 2021 156,779 $ 192.45 74,627 Total employee stock-based compensation cost recognized in income was $19,965,000 and $17,385,000 for the nine months ended September 30, 2021 and 2020, respectively, and total capitalized stock-based compensation cost was $6,899,000 and $8,291,000 for the nine months ended September 30, 2021 and 2020, respectively. At September 30, 2021, there was a total unrecognized compensation cost of $46,683,000 for unvested restricted stock, stock options and performance awards, which does not include forfeitures, and is expected to be recognized over a weighted average period of 1.9 years. Forfeitures are included in compensation cost as they occur.

Related Party Arrangements

Related Party Arrangements	9 Months Ended
	Sep. 30, 2021
Related Party Transactions [Abstract]
Related Party Arrangements	Related Party Arrangements Unconsolidated Entities The Company manages unconsolidated real estate entities for which it receives asset management, property management, development and redevelopment fee revenue. From these entities, the Company earned fees of $695,000 and $1,017,000 for the three months ended September 30, 2021 and 2020, respectively, and $2,380,000 and $2,950,000 for the nine months ended September 30, 2021 and 2020, respectively. In addition, the Company had outstanding receivables associated with its property and construction management roles of $3,374,000 and $5,408,000 as of September 30, 2021 and December 31, 2020, respectively. Director Compensation The Company recorded non-employee director compensation expense relating to restricted stock grants and deferred stock units in the amount of $516,000 and $459,000 in the three months ended September 30, 2021 and 2020, respectively, and $1,457,000 and $1,360,000 in the nine months ended September 30, 2021 and 2020, respectively, as a component of general and administrative expense. Deferred compensation relating to these restricted stock grants and deferred stock units to non-employee directors was $1,119,000 and $614,000 on September 30, 2021 and December 31, 2020, respectively, reported as a component of prepaid expenses and other assets on the accompanying Condensed Consolidated Balance Sheets.

Fair Value

Fair Value	9 Months Ended
	Sep. 30, 2021
Fair Value Disclosures [Abstract]
Fair Value	Fair Value Financial Instruments Carried at Fair Value Derivative Financial Instruments The Company uses interest rate swap and interest rate cap agreements to manage its interest rate risk. These instruments are carried at fair value in the Company's financial statements. In adjusting the fair value of its derivative contracts for the effect of counterparty nonperformance risk, the Company has considered the impact of its net position with a given counterparty, as well as any applicable credit enhancements, such as collateral postings, thresholds, mutual puts and guarantees. The Company minimizes its credit risk on these transactions by dealing with major, creditworthy financial institutions which have an A or better credit rating by the Standard & Poor's Ratings Group. As part of its on-going control procedures, the Company monitors the credit ratings of counterparties and the exposure of the Company to any single entity, thus reducing credit risk concentration. The Company believes the likelihood of realizing losses from counterparty nonperformance is remote. Although the Company has determined that the majority of the inputs used to value its derivatives fall within Level 2 of the fair value hierarchy, such as interest rate, term to maturity and volatility, the credit valuation adjustments associated with its derivatives use Level 3 inputs, such as estimates of current credit spreads, to evaluate the likelihood of default by itself and its counterparties. As of September 30, 2021, the Company assessed the significance of the impact of the credit valuation adjustments on the overall valuation of its derivative positions and has determined it is not significant. As a result, the Company has determined that its derivative valuations are classified in Level 2 of the fair value hierarchy. The following table summarizes the consolidated derivative positions at September 30, 2021 (dollars in thousands): Non-designated Hedges Cash Flow Hedges Interest Rate Caps Interest Rate Swaps Notional balance $ 410,950 $ 150,000 Weighted average interest rate (1) 1.6 % N/A Weighted average swapped/capped interest rate 6.1 % 1.4 % Earliest maturity date November 2021 March 2022 Latest maturity date July 2026 March 2022 ____________________________________ (1) For debt hedged by interest rate caps, represents the weighted average interest rate on the hedged debt prior to any impact of the associated interest rate caps. The following derivative activity occurred during the nine months ended September 30, 2021: • The Company terminated $150,000,000 of forward interest rate swap agreements for which hedge accounting was ceased in 2020, receiving a payment of $6,962,000. The Company recognized $2,894,000 of these proceeds as a gain in 2020, and $2,654,000 of these proceeds as a gain during the nine months ended September 30, 2021 included in interest expense, net on the accompanying Condensed Consolidated Statements of Comprehensive Income. • In conjunction with the issuance of the Company's $700,000,000 2.050% unsecured notes due 2032 in September 2021, the Company settled $200,000,000 of forward interest rate swap agreements, entered into in 2021, designated as cash flow hedges of the interest rate variability on the issuance of the unsecured notes, making a net payment of $2,211,000. The Company has deferred these amounts in accumulated other comprehensive loss on the accompanying Condensed Consolidated Balance Sheets, and is recognizing the impact as a component of interest expense, net, over the term of the respective hedged debt. • The Company entered into an additional $150,000,000 of new forward interest rate swap agreements executed to reduce the impact of variability in interest rates on a portion of the Company's expected debt issuance activity in 2022. At the maturity of the remaining outstanding swap agreements, the Company expects to cash settle the contracts and either pay or receive cash for the then current fair value. Assuming that the Company issues the debt as expected, the hedging impact from these positions will then be recognized over the life of the issued debt as a yield adjustment. The Company is party to five derivatives not designated as hedges at September 30, 2021 for which the fair value changes for the three and nine months ended September 30, 2021 and 2020 were not material. The following table summarizes the deferred losses reclassified from accumulated other comprehensive loss into earnings (dollars in thousands): For the three months ended For the nine months ended 9/30/2021 9/30/2020 9/30/2021 9/30/2020 Cash flow hedge losses reclassified to earnings $ 7,405 $ 2,367 $ 12,138 $ 6,617 The Company anticipates reclassifying approximately $4,051,000 of net hedging losses from accumulated other comprehensive loss into earnings within the next 12 months as an offset to the hedged item during this period. Redeemable Noncontrolling Interests The Company issued units of limited partnership interest in a DownREIT which provides the DownREIT limited partners the ability to present all or some of their units for redemption for cash as determined by the partnership agreement. Under the DownREIT agreement, for each limited partnership unit, the limited partner is entitled to receive cash in the amount equal to the fair value of the Company's common stock on or about the date of redemption. In lieu of cash redemption, the Company may elect to exchange such units for an equal number of shares of the Company's common stock. The limited partnership units in the DownREIT are valued using the market price of the Company's common stock, a Level 1 price under the fair value hierarchy. Financial Instruments Not Carried at Fair Value Cash and Cash Equivalents Cash and cash equivalent balances are held with various financial institutions within accounts designed to preserve principal. The Company monitors credit ratings of these financial institutions and the concentration of cash and cash equivalent balances with any one financial institution and believes the likelihood of realizing material losses related to cash and cash equivalent balances is remote. Cash and cash equivalents are carried at their face amounts, which reasonably approximate their fair values and are Level 1 within the fair value hierarchy. Other Financial Instruments Rents and other receivables and prepaid expenses, accounts and construction payable and accrued expenses and other liabilities are carried at their face amounts, which reasonably approximate their fair values. Indebtedness The Company values its fixed rate unsecured notes using quoted market prices, a Level 1 price within the fair value hierarchy. The Company values its mortgage notes payable, variable rate unsecured notes, Term Loans and outstanding amounts under the Credit Facility using a discounted cash flow analysis on the expected cash flows of each instrument. This analysis reflects the contractual terms of the instrument, including the period to maturity, and uses observable market-based inputs, including interest rate curves. The process also considers credit valuation adjustments to appropriately reflect the Company's nonperformance risk. The Company has concluded that the value of its mortgage notes payable, variable rate unsecured notes, Term Loans and outstanding amounts under the Credit Facility are Level 2 prices as the majority of the inputs used to value its positions fall within Level 2 of the fair value hierarchy. Financial Instruments Measured/Disclosed at Fair Value on a Recurring Basis The following tables summarize the classification between the three levels of the fair value hierarchy of the Company's financial instruments measured/disclosed at fair value on a recurring basis (dollars in thousands): 9/30/2021 Description Total Fair Value Quoted Prices Significant Significant Non Designated Hedges Interest Rate Caps $ 121 $ — $ 121 $ — Interest Rate Swaps - Assets 3,399 — 3,399 — DownREIT units (1,662) (1,662) — — Indebtedness Fixed rate unsecured notes (7,280,382) (7,280,382) — — Mortgage notes payable, variable rate unsecured notes and Term Loans (1,018,373) — (1,018,373) — Total $ (8,296,897) $ (7,282,044) $ (1,014,853) $ — 12/31/2020 Description Total Fair Value Quoted Prices Significant Significant Non Designated Hedges Interest Rate Caps $ 6 $ — $ 6 $ — Interest Rate Swaps - Assets 4,308 — 4,308 — DownREIT units (1,203) (1,203) — — Indebtedness Fixed rate unsecured notes (7,271,799) (7,271,799) — — Mortgage notes payable, variable rate unsecured notes and Term Loans (1,043,976) — (1,043,976) — Total $ (8,312,664) $ (7,273,002) $ (1,039,662) $ —

Subsequent Events

Subsequent Events	9 Months Ended
	Sep. 30, 2021
Subsequent Events [Abstract]
Subsequent Events	Subsequent Events The Company has evaluated subsequent events through the date on which this Form 10-Q was filed, the date on which these financial statements were issued, and identified the items below for discussion. In October 2021, the Company acquired Curv located in Fort Lauderdale, FL, containing 243 apartment homes and 49,000 square feet of commercial space that is 100% leased to Whole Foods Market, for a purchase price of $150,000,000. In October 2021, the Company sold 101,343 shares of common stock under CEP V at an average sales price of $225.85 per share, for net proceeds of $22,545,000. In November 2021, the Company repaid an aggregate of $73,060,000 principal amount of fixed rate debt with a weighted average interest rate of 3.79% secured by Avalon Westbury at par in advance of the November 2036 maturity date. As of November 4, 2021, the Company had $39,000,000 outstanding under the Credit Facility.

Organization, Basis of Presen_2

Organization, Basis of Presentation and Significant Accounting Policies (Policies)	9 Months Ended
	Sep. 30, 2021
Accounting Policies [Abstract]
Organization and Basis of Presentation	Organization and Basis of Presentation AvalonBay Communities, Inc. (the "Company," which term, unless the context otherwise requires, refers to AvalonBay Communities, Inc. together with its subsidiaries) is a Maryland corporation that has elected to be treated as a real estate investment trust ("REIT") for federal income tax purposes under the Internal Revenue Code of 1986, as amended (the "Code"). The Company focuses on the development, redevelopment, acquisition, ownership and operation of multifamily communities in New England, the New York/New Jersey metro area, the Mid-Atlantic, the Pacific Northwest, and Northern and Southern California, as well as in the Company's expansion markets of Raleigh-Durham and Charlotte, North Carolina, Southeast Florida, Dallas and Austin, Texas, and Denver, Colorado. At September 30, 2021, the Company owned or held a direct or indirect ownership interest in 276 operating apartment communities containing 81,968 apartment homes in 13 states and the District of Columbia. In addition, the Company owned or held a direct or indirect ownership interest in 17 communities under development that are expected to contain an aggregate of 5,448 apartment homes when completed, as well as The Park Loggia, which contains 172 for-sale residential condominiums, of which 113 have been sold as of September 30, 2021, and 66,000 square feet of commercial space, of which 87% has been leased as of September 30, 2021. The Company also owned or held a direct or indirect ownership interest in land or rights to land on which the Company expects to develop an additional 22 communities that, if developed as expected, will contain an estimated 7,376 apartment homes. The interim unaudited financial statements have been prepared in accordance with U.S. generally accepted accounting principles ("GAAP") for interim financial information and in conjunction with the rules and regulations of the Securities and Exchange Commission ("SEC"). Certain information and footnote disclosures normally included in financial statements required by GAAP have been condensed or omitted pursuant to such rules and regulations. These unaudited financial statements should be read in conjunction with the financial statements and notes included in the Company's 2020 Annual Report on Form 10-K. The results of operations for the three and nine months ended September 30, 2021 are not necessarily indicative of the operating results for the full year. Management believes the disclosures are adequate to ensure the information presented is not misleading. In the opinion of management, all adjustments and eliminations, consisting only of normal, recurring adjustments necessary for a fair presentation of the financial statements for the interim periods, have been included. Capitalized terms used without definition have meanings provided elsewhere in this Form 10-Q.
Earnings per Common Share	Earnings per Common Share Basic earnings per share is computed by dividing net income attributable to common stockholders by the weighted average number of shares outstanding during the period. All outstanding unvested restricted share awards contain rights to non-forfeitable dividends and participate in undistributed earnings with common shareholders and, accordingly, are considered participating securities that are included in the two-class method of computing basic earnings per share ("EPS"). Both the unvested restricted shares and other potentially dilutive common shares, and the related impact to earnings, are considered when calculating earnings per share on a diluted basis. The Company's earnings per common share are determined as follows (dollars in thousands, except per share data): For the three months ended For the nine months ended 9/30/2021 9/30/2020 9/30/2021 9/30/2020 Basic and diluted shares outstanding Weighted average common shares - basic 139,386,413 140,271,574 139,338,800 140,366,438 Weighted average DownREIT units outstanding 7,500 7,500 7,500 7,500 Effect of dilutive securities 343,812 324,648 298,769 328,865 Weighted average common shares - diluted 139,737,725 140,603,722 139,645,069 140,702,803 Calculation of Earnings per Share - basic Net income attributable to common stockholders $ 78,914 $ 147,703 $ 669,090 $ 486,502 Net income allocated to unvested restricted shares (160) (342) (1,443) (1,158) Net income attributable to common stockholders, adjusted $ 78,754 $ 147,361 $ 667,647 $ 485,344 Weighted average common shares - basic 139,386,413 140,271,574 139,338,800 140,366,438 Earnings per common share - basic $ 0.57 $ 1.05 $ 4.79 $ 3.46 Calculation of Earnings per Share - diluted Net income attributable to common stockholders $ 78,914 $ 147,703 $ 669,090 $ 486,502 Add: noncontrolling interests of DownREIT unitholders in consolidated partnerships 12 12 36 36 Adjusted net income attributable to common stockholders $ 78,926 $ 147,715 $ 669,126 $ 486,538 Weighted average common shares - diluted 139,737,725 140,603,722 139,645,069 140,702,803 Earnings per common share - diluted $ 0.56 $ 1.05 $ 4.79 $ 3.46 All options to purchase shares of common stock outstanding as of September 30, 2021 and 2020 are included in the computation of diluted earnings per share.
Derivative Instruments and Hedging Activities	Derivative Instruments and Hedging Activities The Company enters into interest rate swap and interest rate cap agreements (collectively, "Hedging Derivatives") for interest rate risk management purposes and in conjunction with certain variable rate secured debt to satisfy lender requirements. The Company does not enter into Hedging Derivative transactions for trading or other speculative purposes. The Company assesses the effectiveness of qualifying cash flow and fair value hedges, both at inception and on an on-going basis. Hedge ineffectiveness is reported as a component of interest expense, net. The fair values of Hedging Derivatives that are in an asset position are recorded in prepaid expenses and other assets. The fair value of Hedging Derivatives that are in a liability position are included in accrued expenses and other liabilities. The Company does not present or disclose the fair value of Hedging Derivatives on a net basis. Fair value changes for derivatives that are not in qualifying hedge relationships are reported as a component of interest expense, net. For the Hedging Derivative positions that the Company has determined qualify as effective cash flow hedges, the Company has recorded the cumulative changes in the fair value of Hedging Derivatives in accumulated other comprehensive loss. Amounts recorded in accumulated other comprehensive loss will be reclassified into earnings in the periods in which earnings are affected by the hedged cash flow. The effective portion of the change in fair value of the Hedging Derivatives that the Company has determined qualified as effective fair value hedges is reported as an adjustment to the carrying amount of the corresponding debt being hedged. See Note 11, “Fair Value,” for further discussion of derivative financial instruments.
Legal and Other Contingencies	Legal and Other Contingencies The Company is involved in various claims and/or administrative proceedings that arise in the ordinary course of its business. While no assurances can be given, the Company does not currently believe that any of these outstanding litigation matters, individually or in the aggregate, will have a material adverse effect on its financial condition or results of operations.
Real Estate, Policy	Acquisitions of Investments in Real Estate The Company accounts for acquisitions of investments in real estate in accordance with the authoritative guidance for the initial measurement, which first requires that the Company determine if the real estate investment is the acquisition of an asset or a business combination. Under either model, the Company must identify and determine the fair value of any assets acquired, liabilities assumed and any noncontrolling interest in the acquiree. Typical assets acquired and liabilities assumed include land, building, furniture, fixtures and equipment, debt and identified intangible assets and liabilities, consisting of the value of above or below market leases and in-place leases. In making estimates of fair values for purposes of allocating purchase price, the Company utilizes various sources, including its own analysis of recently acquired and existing comparable properties in its portfolio and other market data. Consideration for acquisitions is typically in the form of cash unless otherwise disclosed. For a business combination, the Company records the assets acquired and liabilities assumed based on the fair value of each respective item. For an asset acquisition, the allocation of the purchase price is based on the relative fair value of the net assets. The Company expenses all applicable acquisition costs for a business combination and capitalizes all applicable acquisition costs for an asset acquisition. The Company expects that acquisitions of individual operating communities will generally be viewed as asset acquisitions.
Use of Estimates	Use of Estimates The preparation of financial statements in conformity with GAAP requires management to make certain estimates and assumptions. These estimates and assumptions affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the dates of the financial statements and the reported amounts of revenue and expenses during the reporting periods. Actual results could differ from those estimates.
Reclassifications	ReclassificationsCertain reclassifications have been made to amounts in prior years' notes to financial statements to conform to current year presentations as a result of changes in held for sale classification, disposition activity and segment classification.
For-Sale Condominium Inventory	For-Sale Condominium Inventory The Company presents for-sale condominium inventory at historical cost and evaluates the condominiums for impairment when potential indicators exist, as further discussed in Note 6, "Real Estate Disposition Activities."
Lessee Considerations	Lessee Considerations The Company assesses whether a contract is or contains a lease based on whether the contract conveys the right to control the use of an identified asset, including specified portions of larger assets, for a period of time in exchange for consideration. The Company’s leases include both fixed and variable lease payments, which are based on an index or rate such as the consumer price index (CPI) or percentage rents based on total sales. Lease payments included in the lease liability include only fixed lease payments including fixed amounts that depend on an index or rate. For leases that have options to extend the term or terminate the lease early, the Company only factored the impact of such options into the lease term if the option was considered reasonably certain to be exercised. The Company determined the discount rate associated with its ground and office leases on a lease by lease basis using the Company’s actual borrowing rates as well as indicative market pricing for longer term rates and taking into consideration the remaining term of each of the lease agreements.
Lessor Considerations	Lessor Considerations The Company evaluates leases in which it is the lessor, which are composed of residential and commercial leases at its apartment communities, and determined these leases to be operating leases. For lease agreements that provide for rent concessions and/or scheduled fixed and determinable rent increases, rental income is recognized on a straight-line basis over the noncancellable term of the lease, which, for residential leases, is generally one year. Some of the Company’s commercial leases have fixed-price renewal options, and the lessee may be able to exercise its renewal option at an amount less than the fair value of the rent at such time. The Company only includes renewal options in the lease term if, at the commencement of the lease, it is reasonably certain that the lessee will exercise this option. Additionally, for the Company’s residential and commercial leases, which are comprised of the lease component and common area maintenance as a non-lease component, the Company determined that (i) the leases are operating leases, (ii) the lease component is the predominant component and (iii) all components of its operating leases share the same timing and pattern of transfer.
Revenue from Contract with Customer	Revenue and Gain Recognition Revenue from contracts with customers is recognized in accordance with the transfer of goods and services to customers at an amount that reflects the consideration that the Company expects to be entitled to for those goods and services. The majority of the Company’s revenue is derived from residential and commercial rental income and other lease income, which are accounted for under ASC 842, Leases, discussed above. The Company's revenue streams that are not accounted for under ASC 842 include (i) management fees, (ii) rental and non-rental related income and (iii) gains or losses on the sale of real estate. The following table provides details of the Company’s revenue streams disaggregated by the Company’s reportable operating segments, further discussed in Note 8, “Segment Reporting,” for the three and nine months ended September 30, 2021 and 2020. Segment information for total revenue has been adjusted to exclude the real estate assets that were sold from January 1, 2020 through September 30, 2021, or otherwise qualify as held for sale as of September 30, 2021, as described in Note 6, "Real Estate Disposition Activities" (dollars in thousands): For the three months ended Same Store Other Development/ Non- Total For the period ended September 30, 2021 Management, development and other fees and other ancillary items $ — $ — $ — $ 695 $ 695 Rental and non-rental related income (2) 1,883 369 171 — 2,423 Total non-lease revenue (3) 1,883 369 171 695 3,118 Lease income (4) 517,914 27,539 28,372 — 573,825 Business interruption insurance proceeds — — — — — Total revenue $ 519,797 $ 27,908 $ 28,543 $ 695 $ 576,943 For the period ended September 30, 2020 Management, development and other fees and other ancillary items $ — $ — $ — $ 419 $ 419 Rental and non-rental related income (2) 1,965 598 112 — 2,675 Total non-lease revenue (3) 1,965 598 112 419 3,094 Lease income (4) 511,171 21,718 6,831 — 539,720 Business interruption insurance proceeds 282 — — — 282 Total revenue $ 513,418 $ 22,316 $ 6,943 $ 419 $ 543,096 For the nine months ended Same Store Other Development/ Non- Total For the period ended September 30, 2021 Management, development and other fees and other ancillary items $ — $ — $ — $ 2,380 $ 2,380 Rental and non-rental related income (2) 5,469 1,148 483 — 7,100 Total non-lease revenue (3) 5,469 1,148 483 2,380 9,480 Lease income (4) 1,514,951 75,886 65,060 — 1,655,897 Business interruption insurance proceeds — — — — — Total revenue $ 1,520,420 $ 77,034 $ 65,543 $ 2,380 $ 1,665,377 For the period ended September 30, 2020 Management, development and other fees and other ancillary items $ — $ — $ — $ 1,109 $ 1,109 Rental and non-rental related income (2) 5,447 1,637 230 — 7,314 Total non-lease revenue (3) 5,447 1,637 230 1,109 8,423 Lease income (4) 1,580,580 63,325 16,889 — 1,660,794 Business interruption insurance proceeds 378 — — — 378 Total revenue $ 1,586,405 $ 64,962 $ 17,119 $ 1,109 $ 1,669,595 __________________________________ (1) Revenue represents third-party management, asset management and developer fees and miscellaneous income and other ancillary items which are not allocated to a reportable segment. (2) Amounts include revenue streams related to leasing activities that are not considered components of a lease, including but not limited to, apartment hold fees and application fees, as well as revenue streams not related to leasing activities, including but not limited to, vendor revenue sharing, building advertising, vending and dry cleaning revenue. (3) Represents all revenue accounted for under ASC 606, Revenue from Contracts with Customers. (4) Amounts include all revenue streams derived from residential and commercial rental income and other lease income, which are accounted for under ASC 842. Due to the nature and timing of the Company’s identified revenue streams, there are no material amounts of outstanding or unsatisfied performance obligations as of September 30, 2021.
Revenue Recognition, Leases	Lease Revenue Reserves The Company assesses the collectability of its lease revenue and receivables on an on-going basis. Under ASC 842, Leases, the Company assesses the probability of receiving all remaining lease amounts due on a lease by lease basis, reserving for revenue and the related receivables for those leases where collection of substantially all of the remaining lease payments is not probable. Subsequently, the Company will only recognize revenue to the extent cash is received. If the Company determines that collection of the remaining lease payments becomes probable at a future date, the Company will recognize the cumulative revenue that would have been recorded under the original lease agreement. In addition to the specific reserves recognized under ASC 842, the Company also evaluates its lease receivables for collectability at a portfolio level under ASC 450, Contingencies – Loss Contingencies. The Company recognizes a reserve under ASC 450 when the uncollectible revenue is probable and reasonably estimable.
COVID-19 Pandemic	COVID-19 Pandemic In March 2020, the World Health Organization designated COVID-19 as a pandemic. While the Company has taken various actions in response to the COVID-19 pandemic, the ultimate impact on its consolidated results of operations, cash flows, financial condition and liquidity will depend on, among other factors, (i) the effect on the multifamily industry and the general economy of measures taken by businesses and the government to prevent the spread of the novel coronavirus and relieve economic distress of consumers, such as governmental limitations on the ability of multifamily owners to evict residents who are delinquent in the payment of their rent and (ii) the preferences of consumers and businesses for living and working arrangements both during and after the pandemic. As of September 30, 2021, the Company assessed the collectibility of the outstanding lease income receivables as a result of the impact of the COVID-19 pandemic on its residential and commercial lease portfolios. The Company recorded an aggregate offset to income for uncollectible lease revenue for its residential and commercial portfolios of $8,586,000 and $18,755,000 for the three months ended September 30, 2021 and 2020, respectively, and $42,295,000 and $43,034,000 for the nine months ended September 30, 2021 and 2020, respectively, under ASC 842 and ASC 450.

Organization, Basis of Presen_3

Organization, Basis of Presentation and Significant Accounting Policies (Tables)	9 Months Ended
	Sep. 30, 2021
Accounting Policies [Abstract]
Schedule of earnings per common share	The Company's earnings per common share are determined as follows (dollars in thousands, except per share data): For the three months ended For the nine months ended 9/30/2021 9/30/2020 9/30/2021 9/30/2020 Basic and diluted shares outstanding Weighted average common shares - basic 139,386,413 140,271,574 139,338,800 140,366,438 Weighted average DownREIT units outstanding 7,500 7,500 7,500 7,500 Effect of dilutive securities 343,812 324,648 298,769 328,865 Weighted average common shares - diluted 139,737,725 140,603,722 139,645,069 140,702,803 Calculation of Earnings per Share - basic Net income attributable to common stockholders $ 78,914 $ 147,703 $ 669,090 $ 486,502 Net income allocated to unvested restricted shares (160) (342) (1,443) (1,158) Net income attributable to common stockholders, adjusted $ 78,754 $ 147,361 $ 667,647 $ 485,344 Weighted average common shares - basic 139,386,413 140,271,574 139,338,800 140,366,438 Earnings per common share - basic $ 0.57 $ 1.05 $ 4.79 $ 3.46 Calculation of Earnings per Share - diluted Net income attributable to common stockholders $ 78,914 $ 147,703 $ 669,090 $ 486,502 Add: noncontrolling interests of DownREIT unitholders in consolidated partnerships 12 12 36 36 Adjusted net income attributable to common stockholders $ 78,926 $ 147,715 $ 669,126 $ 486,538 Weighted average common shares - diluted 139,737,725 140,603,722 139,645,069 140,702,803 Earnings per common share - diluted $ 0.56 $ 1.05 $ 4.79 $ 3.46
Disaggregation of revenue	The following table provides details of the Company’s revenue streams disaggregated by the Company’s reportable operating segments, further discussed in Note 8, “Segment Reporting,” for the three and nine months ended September 30, 2021 and 2020. Segment information for total revenue has been adjusted to exclude the real estate assets that were sold from January 1, 2020 through September 30, 2021, or otherwise qualify as held for sale as of September 30, 2021, as described in Note 6, "Real Estate Disposition Activities" (dollars in thousands): For the three months ended Same Store Other Development/ Non- Total For the period ended September 30, 2021 Management, development and other fees and other ancillary items $ — $ — $ — $ 695 $ 695 Rental and non-rental related income (2) 1,883 369 171 — 2,423 Total non-lease revenue (3) 1,883 369 171 695 3,118 Lease income (4) 517,914 27,539 28,372 — 573,825 Business interruption insurance proceeds — — — — — Total revenue $ 519,797 $ 27,908 $ 28,543 $ 695 $ 576,943 For the period ended September 30, 2020 Management, development and other fees and other ancillary items $ — $ — $ — $ 419 $ 419 Rental and non-rental related income (2) 1,965 598 112 — 2,675 Total non-lease revenue (3) 1,965 598 112 419 3,094 Lease income (4) 511,171 21,718 6,831 — 539,720 Business interruption insurance proceeds 282 — — — 282 Total revenue $ 513,418 $ 22,316 $ 6,943 $ 419 $ 543,096 For the nine months ended Same Store Other Development/ Non- Total For the period ended September 30, 2021 Management, development and other fees and other ancillary items $ — $ — $ — $ 2,380 $ 2,380 Rental and non-rental related income (2) 5,469 1,148 483 — 7,100 Total non-lease revenue (3) 5,469 1,148 483 2,380 9,480 Lease income (4) 1,514,951 75,886 65,060 — 1,655,897 Business interruption insurance proceeds — — — — — Total revenue $ 1,520,420 $ 77,034 $ 65,543 $ 2,380 $ 1,665,377 For the period ended September 30, 2020 Management, development and other fees and other ancillary items $ — $ — $ — $ 1,109 $ 1,109 Rental and non-rental related income (2) 5,447 1,637 230 — 7,314 Total non-lease revenue (3) 5,447 1,637 230 1,109 8,423 Lease income (4) 1,580,580 63,325 16,889 — 1,660,794 Business interruption insurance proceeds 378 — — — 378 Total revenue $ 1,586,405 $ 64,962 $ 17,119 $ 1,109 $ 1,669,595 __________________________________ (1) Revenue represents third-party management, asset management and developer fees and miscellaneous income and other ancillary items which are not allocated to a reportable segment. (2) Amounts include revenue streams related to leasing activities that are not considered components of a lease, including but not limited to, apartment hold fees and application fees, as well as revenue streams not related to leasing activities, including but not limited to, vendor revenue sharing, building advertising, vending and dry cleaning revenue. (3) Represents all revenue accounted for under ASC 606, Revenue from Contracts with Customers. (4) Amounts include all revenue streams derived from residential and commercial rental income and other lease income, which are accounted for under ASC 842.

Mortgage Notes Payable, Unsec_2

Mortgage Notes Payable, Unsecured Notes and Credit Facility (Tables)	9 Months Ended
	Sep. 30, 2021
Debt Disclosure [Abstract]
Summary of company's mortgage notes payable, unsecured notes and Credit Facility excluding mortgage notes secured by communities classified as held for sale	The following amounts and discussion do not include the mortgage notes related to the communities classified as held for sale, if any, as of September 30, 2021 and December 31, 2020, as shown in the accompanying Condensed Consolidated Balance Sheets (dollars in thousands) (see Note 6, "Real Estate Disposition Activities"). 9/30/2021 12/31/2020 Fixed rate unsecured notes (1) $ 6,750,000 $ 6,500,000 Term Loans (1) 250,000 250,000 Fixed rate mortgage notes payable - conventional and tax-exempt (2) 379,636 408,964 Variable rate mortgage notes payable - conventional and tax-exempt (2) 464,650 470,850 Total mortgage notes payable and unsecured notes and Term Loans 7,844,286 7,629,814 Credit Facility — — Total mortgage notes payable, unsecured notes, Term Loans and Credit Facility $ 7,844,286 $ 7,629,814 _____________________________________ (1) Balances at September 30, 2021 and December 31, 2020 exclude $9,915 and $10,380, respectively, of debt discount, and $38,448 and $37,615, respectively, of deferred financing costs, as reflected in unsecured notes, net on the accompanying Condensed Consolidated Balance Sheets. (2) Balances at September 30, 2021 and December 31, 2020 exclude $13,806 and $14,478, respectively, of debt discount, and $2,813 and $3,004, respectively, of deferred financing costs, as reflected in mortgage notes payable, net on the accompanying Condensed Consolidated Balance Sheets.
Scheduled payments and maturities of mortgage notes payable and unsecured notes outstanding	Scheduled payments and maturities of secured notes payable and unsecured notes outstanding at September 30, 2021 are as follows (dollars in thousands): Year Secured notes Secured notes maturities Unsecured notes and Term Loans maturities Stated interest rate of unsecured notes and Term Loans 2021 $ 1,460 $ — $ — N/A 2022 9,918 — — N/A 100,000 LIBOR + 0.90% 2023 10,739 — 350,000 4.200 % 250,000 2.850 % 2024 11,677 — 300,000 3.500 % 150,000 LIBOR + 0.85% 2025 12,408 — 525,000 3.450 % 300,000 3.500 % 2026 13,445 — 475,000 2.950 % 300,000 2.900 % 2027 15,880 236,100 400,000 3.350 % 2028 20,707 — 450,000 3.200 % 2029 11,742 66,250 450,000 3.300 % 2030 12,384 — 700,000 2.300 % Thereafter 176,078 245,498 600,000 2.450 % 700,000 2.050 % 350,000 3.900 % 300,000 4.150 % 300,000 4.350 % $ 296,438 $ 547,848 $ 7,000,000

Equity (Tables)

Equity (Tables)	9 Months Ended
	Sep. 30, 2021
Stockholders' Equity Note [Abstract]
Summary of changes in equity	The following summarizes the changes in equity for the nine months ended September 30, 2021 (dollars in thousands): Common Additional Accumulated Accumulated Total stockholder's equity Noncontrolling interests Total Balance at December 31, 2020 $ 1,395 $ 10,664,416 $ 126,022 $ (40,250) $ 10,751,583 $ 591 $ 10,752,174 Net income attributable to common stockholders — — 142,223 — 142,223 — 142,223 Cash flow hedge losses reclassified to earnings — — — 2,367 2,367 — 2,367 Change in redemption value of redeemable noncontrolling interest — — (273) — (273) — (273) Noncontrolling interest distribution and income allocation — — — — — (16) (16) Dividends declared to common stockholders ($1.59 per share) — — (221,779) — (221,779) — (221,779) Issuance of common stock, net of withholdings 1 (14,037) 958 — (13,078) — (13,078) Amortization of deferred compensation — 7,286 — — 7,286 — 7,286 Balance at March 31, 2021 $ 1,396 $ 10,657,665 $ 47,151 $ (37,883) $ 10,668,329 $ 575 $ 10,668,904 Net income attributable to common stockholders — — 447,953 — 447,953 — 447,953 Loss on cash flow hedges, net — — — (822) (822) — (822) Cash flow hedge losses reclassified to earnings — — — 2,366 2,366 — 2,366 Change in redemption value of redeemable noncontrolling interest — — (255) — (255) — (255) Noncontrolling interest distribution and income allocation — — — — — (7) (7) Dividends declared to common stockholders ($1.59 per share) — — (222,451) — (222,451) — (222,451) Issuance of common stock, net of withholdings — 2,496 — — 2,496 — 2,496 Amortization of deferred compensation — 10,403 — — 10,403 — 10,403 Balance at June 30, 2021 $ 1,396 $ 10,670,564 $ 272,398 $ (36,339) $ 10,908,019 $ 568 $ 10,908,587 Net income attributable to common stockholders — — 78,914 — 78,914 — 78,914 Gain on cash flow hedges, net — — — 2,010 2,010 — 2,010 Cash flow hedge losses reclassified to earnings — — — 7,405 7,405 — 7,405 Change in redemption value of redeemable noncontrolling interest — — (261) — (261) — (261) Noncontrolling interest distribution and income allocation — — — — — 2 2 Dividends declared to common stockholders ($1.59 per share) — — (222,475) — (222,475) — (222,475) Issuance of common stock, net of withholdings — 4,633 (27) — 4,606 — 4,606 Amortization of deferred compensation — 9,442 — — 9,442 — 9,442 Balance at September 30, 2021 $ 1,396 $ 10,684,639 $ 128,549 $ (26,924) $ 10,787,660 $ 570 $ 10,788,230 The following summarizes the changes in equity for the nine months ended September 30, 2020 (dollars in thousands): Common Additional Accumulated Accumulated Total stockholder's equity Noncontrolling interests Total Balance at December 31, 2019 $ 1,406 $ 10,736,733 $ 282,913 $ (31,503) $ 10,989,549 $ 649 $ 10,990,198 Net income attributable to common stockholders — — 167,971 — 167,971 — 167,971 Loss on cash flow hedges, net — — — (17,603) (17,603) — (17,603) Cash flow hedge losses reclassified to earnings — — — 1,949 1,949 — 1,949 Change in redemption value of redeemable noncontrolling interest — — 471 — 471 — 471 Noncontrolling interests income allocation — — — — — (35) (35) Dividends declared to common stockholders ($1.59 per share) — — (224,083) — (224,083) — (224,083) Issuance of common stock, net of withholdings 1 (12,492) (1,616) — (14,107) — (14,107) Amortization of deferred compensation — 7,781 — — 7,781 — 7,781 Balance at March 31, 2020 $ 1,407 $ 10,732,022 $ 225,656 $ (47,157) $ 10,911,928 $ 614 $ 10,912,542 Net income attributable to common stockholders — — 170,828 — 170,828 — 170,828 Loss on cash flow hedges, net — — — (1,461) (1,461) — (1,461) Cash flow hedge losses reclassified to earnings — — — 2,301 2,301 — 2,301 Change in redemption value of redeemable noncontrolling interest — — (146) — (146) — (146) Noncontrolling interests income allocation — — — — — 1 1 Dividends declared to common stockholders ($1.59 per share) — — (224,172) — (224,172) — (224,172) Issuance of common stock, net of withholdings — 1,050 138 — 1,188 — 1,188 Amortization of deferred compensation — 9,724 — — 9,724 — 9,724 Balance at June 30, 2020 $ 1,407 $ 10,742,796 $ 172,304 $ (46,317) $ 10,870,190 $ 615 $ 10,870,805 Net income attributable to common stockholders — — 147,703 — 147,703 — 147,703 Gain on cash flow hedges, net — — — 1,333 1,333 — 1,333 Cash flow hedge losses reclassified to earnings — — — 2,367 2,367 — 2,367 Change in redemption value of redeemable noncontrolling interest — — 62 — 62 — 62 Noncontrolling interest distribution and income allocation — — — — — (17) (17) Dividends declared to common stockholders ($1.59 per share) — — (222,694) — (222,694) — (222,694) Issuance of common stock, net of withholdings — 105 — — 105 — 105 Repurchase of common stock, including repurchase costs (9) (69,779) (67,670) — (137,458) — (137,458) Amortization of deferred compensation — 8,036 — — 8,036 — 8,036 Balance at September 30, 2020 $ 1,398 $ 10,681,158 $ 29,705 $ (42,617) $ 10,669,644 $ 598 $ 10,670,242

Investments in Real Estate En_2

Investments in Real Estate Entities (Tables)	9 Months Ended
	Sep. 30, 2021
Equity Method Investments and Joint Ventures [Abstract]
Summary of financial information of equity method investments	The following is a combined summary of the financial position of the entities accounted for using the equity method or the measurement alternative discussed above as of the dates presented, including development joint ventures started and unconsolidated communities sold during the respective periods (dollars in thousands): 9/30/2021 12/31/2020 (unaudited) Assets: Real estate, net $ 1,171,955 $ 1,249,730 Other assets 326,339 255,606 Total assets $ 1,498,294 $ 1,505,336 Liabilities and partners' capital: Mortgage notes payable, net (1) $ 636,796 $ 751,257 Other liabilities 172,660 163,808 Partners' capital 688,838 590,271 Total liabilities and partners' capital $ 1,498,294 $ 1,505,336 _________________________________ (1) Includes the variable rate construction loan secured by AVA Arts District, of which $1,032,000 has been drawn as of September 30, 2021 . The Company has guaranteed the construction loan on behalf of the venture, and any obligations the Company may incur under the guarantee, except for those due to misconduct by the Company, are required capital contributions of the partners based on ownership interest. The Company has not guaranteed any other outstanding debt, nor does the Company have any obligation to fund this debt should the unconsolidated entity be unable to do so. The following is a combined summary of the operating results of the entities accounted for using the equity method discussed above for the periods presented (dollars in thousands): For the three months ended For the nine months ended 9/30/2021 9/30/2020 9/30/2021 9/30/2020 (unaudited) (unaudited) Rental and other income (1) $ 44,819 $ 28,800 $ 111,562 $ 92,299 Operating and other expenses (10,698) (12,782) (34,992) (37,034) Gain on sale of communities — 18,408 164,317 18,448 Interest expense, net (6,137) (8,024) (21,386) (24,133) Depreciation expense (6,912) (8,704) (22,831) (26,106) Net income $ 21,072 $ 17,698 $ 196,670 $ 23,474 Company's share of net income from investments in unconsolidated entities $ 7,287 $ 5,611 $ 34,435 $ 8,357 Amortization of excess investment and other (420) (528) (1,476) (1,587) Income from investments in unconsolidated entities $ 6,867 $ 5,083 $ 32,959 $ 6,770 _________________________________

Real Estate Disposition Activ_2

Real Estate Disposition Activities (Tables)	9 Months Ended
	Sep. 30, 2021
Discontinued Operations and Disposal Groups [Abstract]
Real estate sales	The following real estate sales occurred during the nine months ended September 30, 2021: Community name Location Period of sale Apartment homes Gross sales price Gain on eaves Stamford Stamford, CT Q121 238 $ 72,000 $ 53,775 Avalon Norwalk Norwalk, CT Q221 311 $ 103,000 $ 48,912 AVA Cortez Hill San Diego, CA Q221 299 $ 96,500 $ 75,716 Avalon Redmond Place Redmond, WA Q221 222 $ 97,700 $ 72,929 Avalon Bronxville Bronxville, NY Q221 110 $ 89,000 $ 71,773 Avalon Glen Cove & Avalon Glen Cove North Glen Cove, NY Q221 367 $ 126,000 $ 65,242 _________________________________ (1) Gain on disposition was reported in gain on sale of communities on the accompanying Condensed Consolidated Statements of Comprehensive Income.

Segment Reporting (Tables)

Segment Reporting (Tables)	9 Months Ended
	Sep. 30, 2021
Segment Reporting [Abstract]
Schedule of reconciliation of NOI to net income	A reconciliation of NOI to net income for the three and nine months ended September 30, 2021 and 2020 is as follows (dollars in thousands): For the three months ended For the nine months ended 9/30/2021 9/30/2020 9/30/2021 9/30/2020 Net income $ 78,847 $ 147,717 $ 669,058 $ 486,592 Property management and other indirect operating expenses, net of corporate income 25,322 23,837 74,110 70,043 Expensed transaction, development and other pursuit costs, net of recoveries 417 567 1,900 4,289 Interest expense, net 55,987 53,249 164,704 162,562 Loss (gain) on extinguishment of debt, net 17,890 (105) 17,768 9,333 General and administrative expense 17,313 13,985 53,130 46,878 Income from investments in unconsolidated entities (6,867) (5,083) (32,959) (6,770) Depreciation expense 193,791 175,348 561,560 529,508 Income tax expense (benefit) 2,179 (27) 1,434 (1,069) Casualty and impairment loss 1,940 — 3,117 — Gain on sale of communities (58) (31,607) (388,354) (91,338) Gain on other real estate transactions, net (1,543) (129) (2,002) (328) Net for-sale condominium activity (158) 646 1,402 (4,162) Net operating income from real estate assets sold or held for sale (2,373) (14,686) (17,393) (47,798) Net operating income $ 382,687 $ 363,712 $ 1,107,475 $ 1,157,740
Schedule of net operating income from real estate assets sold or held for sale, not classified as discontinued operations	The following is a summary of NOI from real estate assets sold or held for sale for the periods presented (dollars in thousands): For the three months ended For the nine months ended 9/30/2021 9/30/2020 9/30/2021 9/30/2020 Rental income from real estate assets sold or held for sale $ 3,831 $ 24,308 $ 28,276 $ 75,864 Operating expenses from real estate assets sold or held for sale (1,458) (9,622) (10,883) (28,066) Net operating income from real estate assets sold or held for sale $ 2,373 $ 14,686 $ 17,393 $ 47,798
Schedule of details of segment information	The following table provides details of the Company's segment information as of the dates specified (dollars in thousands). The segments are classified based on the individual community's status at January 1, 2021. Segment information for the three and nine months ended September 30, 2021 and 2020 has been adjusted to exclude the real estate assets that were sold from January 1, 2020 through September 30, 2021, or otherwise qualify as held for sale as of September 30, 2021, as described in Note 6, "Real Estate Disposition Activities." For the three months ended For the nine months ended Total NOI Total NOI Gross real estate (1) For the period ended September 30, 2021 Same Store New England $ 77,037 $ 48,115 $ 224,614 $ 142,278 $ 2,781,806 Metro NY/NJ 108,776 72,564 319,079 215,147 4,129,121 Mid-Atlantic 85,328 56,103 252,271 168,359 3,575,978 Southeast Florida 8,152 5,026 23,099 13,772 395,594 Denver, CO 6,070 4,011 17,576 11,965 320,214 Pacific Northwest 28,092 19,197 81,640 55,389 1,057,166 Northern California 90,127 63,088 270,124 190,658 3,458,280 Southern California 116,215 79,590 332,017 225,489 4,382,656 Total Same Store 519,797 347,694 1,520,420 1,023,057 20,100,815 Other Stabilized 27,908 18,217 77,034 49,796 1,528,196 Development / Redevelopment 28,543 16,776 65,543 34,622 2,401,751 Land Held for Development N/A N/A N/A N/A 66,769 Non-allocated (2) 695 N/A 2,380 N/A 278,779 Total $ 576,943 $ 382,687 $ 1,665,377 $ 1,107,475 $ 24,376,310 For the period ended September 30, 2020 Same Store New England $ 75,394 $ 48,290 $ 231,478 $ 152,589 $ 2,756,835 Metro NY/NJ 106,542 72,283 325,807 225,793 4,102,402 Mid-Atlantic 84,974 56,721 261,932 182,503 3,550,373 Southeast Florida 6,950 3,331 21,818 11,755 393,594 Denver, CO 5,422 3,418 15,758 10,084 319,038 Pacific Northwest 27,545 18,913 84,808 59,977 1,051,451 Northern California 97,777 71,207 308,522 232,470 3,430,831 Southern California 108,814 72,995 336,282 233,666 4,349,770 Total Same Store 513,418 347,158 1,586,405 1,108,837 19,954,294 Other Stabilized 22,316 14,238 64,962 42,251 1,125,829 Development / Redevelopment 6,943 2,316 17,119 6,652 1,698,823 Land Held for Development N/A N/A N/A N/A 43,494 Non-allocated (2) 419 N/A 1,109 N/A 399,048 Total $ 543,096 $ 363,712 $ 1,669,595 $ 1,157,740 $ 23,221,488 __________________________________ (1) Does not include gross real estate assets held for sale of $89,529 as of September 30, 2021 and gross real estate assets either sold or classified as held for sale subsequent to September 30, 2020 of $720,432. (2) Revenue represents third-party management, accounting, and developer fees and miscellaneous income and other ancillary items which are not allocated to a reportable segment. Gross real estate includes the for-sale residential condominiums at The Park Loggia, as discussed in Note 6, "Real Estate Disposition Activities."

Stock-Based Compensation Plans

Stock-Based Compensation Plans (Tables)	9 Months Ended
	Sep. 30, 2021
Share-based Payment Arrangement [Abstract]
Share-based Payment Arrangement, Option, Activity	Information with respect to stock options granted under the Company's Second Amended and Restated 2009 Equity Incentive Plan (the "2009 Plan") for the three and nine months ended September 30, 2021, is as follows: 2009 Plan Weighted average Options Outstanding, December 31, 2020 12,506 $ 129.35 Exercised (2,126) 121.78 Granted (1) 294,115 180.32 Forfeited (4,713) 180.32 Options Outstanding, September 30, 2021 299,782 $ 178.61 Options Exercisable, September 30, 2021 10,380 $ 130.90 __________________________________
Summary of valuation options	The assumptions used are as follows: 2021 Dividend yield 3.5% Estimated volatility 27.1% Risk free rate 0.81% Expected life of options 5 years Estimated fair value $28.64 The Company used a Monte Carlo model to assess the compensation cost associated with the portion of the performance awards granted in 2021 for which achievement will be determined by using total shareholder return measures. The assumptions used are as follows: 2021 Dividend yield 3.5% Estimated volatility over the life of the plan (1) 22.0% - 49.0% Risk free rate 0.06% - 0.38% Estimated performance award value based on total shareholder return measure $213.16 __________________________________ (1) Estimated volatility over the life of the plan is using 50% historical volatility and 50% implied volatility.
Schedule of nonvested performance awards granted	Information with respect to performance awards granted is as follows: Performance awards Weighted average grant date fair value per award Outstanding at December 31, 2020 241,921 $ 195.13 Granted (1) 138,033 191.12 Change in awards based on performance (2) (37,469) 156.00 Converted to shares of common stock (56,545) 156.00 Forfeited (1,418) 207.65 Outstanding at September 30, 2021 284,522 $ 206.05 __________________________________ (1) The amount of shares of common stock that ultimately may be earned is based on the total shareholder return metrics related to the Company's common stock for 69,064 performance awards and financial metrics related to operating performance, net asset value and leverage metrics of the Company for 68,969 performance awards. (2) Represents the change in the number of performance awards earned based on performance achievement for the performance period.
Schedule of restricted stock granted	Information with respect to restricted stock granted is as follows: Restricted stock shares Restricted stock shares weighted average grant date fair value per share Restricted stock shares converted from performance awards Outstanding at December 31, 2020 131,724 $ 203.28 146,319 Granted - restricted stock shares 96,834 177.49 — Vested - restricted stock shares (68,702) 192.07 (71,692) Forfeited (3,077) 193.47 — Outstanding at September 30, 2021 156,779 $ 192.45 74,627

Fair Value (Tables)

Fair Value (Tables)	9 Months Ended
	Sep. 30, 2021
Fair Value Disclosures [Abstract]
Schedule of summary of consolidated Hedging Derivatives, excluding derivatives executed to hedge debt on communities classified as held for sale	The following table summarizes the consolidated derivative positions at September 30, 2021 (dollars in thousands): Non-designated Hedges Cash Flow Hedges Interest Rate Caps Interest Rate Swaps Notional balance $ 410,950 $ 150,000 Weighted average interest rate (1) 1.6 % N/A Weighted average swapped/capped interest rate 6.1 % 1.4 % Earliest maturity date November 2021 March 2022 Latest maturity date July 2026 March 2022 ____________________________________ (1) For debt hedged by interest rate caps, represents the weighted average interest rate on the hedged debt prior to any impact of the associated interest rate caps.
Schedule of Cash Flow Hedges Included in Accumulated Other Comprehensive Income (Loss)	The following table summarizes the deferred losses reclassified from accumulated other comprehensive loss into earnings (dollars in thousands): For the three months ended For the nine months ended 9/30/2021 9/30/2020 9/30/2021 9/30/2020 Cash flow hedge losses reclassified to earnings $ 7,405 $ 2,367 $ 12,138 $ 6,617
Schedule of summary of classification between the three levels of the fair value hierarchy of the Company's financial instruments measured at fair value on a recurring basis	The following tables summarize the classification between the three levels of the fair value hierarchy of the Company's financial instruments measured/disclosed at fair value on a recurring basis (dollars in thousands): 9/30/2021 Description Total Fair Value Quoted Prices Significant Significant Non Designated Hedges Interest Rate Caps $ 121 $ — $ 121 $ — Interest Rate Swaps - Assets 3,399 — 3,399 — DownREIT units (1,662) (1,662) — — Indebtedness Fixed rate unsecured notes (7,280,382) (7,280,382) — — Mortgage notes payable, variable rate unsecured notes and Term Loans (1,018,373) — (1,018,373) — Total $ (8,296,897) $ (7,282,044) $ (1,014,853) $ — 12/31/2020 Description Total Fair Value Quoted Prices Significant Significant Non Designated Hedges Interest Rate Caps $ 6 $ — $ 6 $ — Interest Rate Swaps - Assets 4,308 — 4,308 — DownREIT units (1,203) (1,203) — — Indebtedness Fixed rate unsecured notes (7,271,799) (7,271,799) — — Mortgage notes payable, variable rate unsecured notes and Term Loans (1,043,976) — (1,043,976) — Total $ (8,312,664) $ (7,273,002) $ (1,039,662) $ —

Organization, Basis of Presen_4

Organization, Basis of Presentation and Significant Accounting Policies (Details) ft² in Thousands, $ in Thousands	3 Months Ended		9 Months Ended		21 Months Ended
	Sep. 30, 2021USD ($)homeresidential_condominiumft²communitystate	Sep. 30, 2020USD ($)	Sep. 30, 2021USD ($)homeresidential_condominiumft²communitystate	Sep. 30, 2020USD ($)	Sep. 30, 2021homeresidential_condominiumft²communitystate
Real Estate Properties [Line Items]
Number of operating apartment communities | community	276		276		276
Number of apartment homes included in operating apartment communities owned | home	81,968		81,968		81,968
Number of states where operating apartment communities owned are located | state	13		13		13
Number of owned communities under construction | community	17		17		17
Expected number of apartment homes under construction | home	5,448		5,448		5,448
Number of Residential Condominium Units Sold | residential_condominium	17		43		113
Communities under development rights | community	22		22		22
Estimated number of apartment homes in communities to be developed | home	7,376		7,376		7,376
Accounts Receivable, Credit Loss Expense (Reversal) | $	$ 8,586	$ 18,755	$ 42,295	$ 43,034
The Park Loggia
Real Estate Properties [Line Items]
Number Of Residential Condominium Units | residential_condominium	172		172		172
Commercial Square Feet | ft²	66		66		66
Percent of Commercial Square Feet Leased	87.00%		87.00%		87.00%

Organization, Basis of Presen_5

Organization, Basis of Presentation and Significant Accounting Policies (Details 2) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2021	Sep. 30, 2020
Basic and diluted shares outstanding
Weighted average common shares - basic (in shares)	139,386,413			140,271,574			139,338,800	140,366,438
Weighted average DownREIT units outstanding (in shares)	7,500			7,500			7,500	7,500
Effect of dilutive securities (in shares)	343,812			324,648			298,769	328,865
Weighted average common shares - diluted (in shares)	139,737,725			140,603,722			139,645,069	140,702,803
Calculation of Earnings per Share - basic
Net income attributable to common stockholders	$ 78,914	$ 447,953	$ 142,223	$ 147,703	$ 170,828	$ 167,971	$ 669,090	$ 486,502
Net income allocated to unvested restricted shares	(160)			(342)			(1,443)	(1,158)
Net income attributable to common stockholders, adjusted	$ 78,754			$ 147,361			$ 667,647	$ 485,344
Weighted average common shares - basic (in shares)	139,386,413			140,271,574			139,338,800	140,366,438
Earnings per common share - basic (in dollars per share)	$ 0.57			$ 1.05			$ 4.79	$ 3.46
Calculation of Earnings per Share - diluted
Net income attributable to common stockholders	$ 78,914	$ 447,953	$ 142,223	$ 147,703	$ 170,828	$ 167,971	$ 669,090	$ 486,502
Add: noncontrolling interests of DownREIT unitholders in consolidated partnerships	12			12			36	36
Adjusted net income attributable to common stockholders	$ 78,926			$ 147,715			$ 669,126	$ 486,538
Weighted average common shares - diluted (in shares)	139,737,725			140,603,722			139,645,069	140,702,803
Earnings per common share - diluted (in dollars per share)	$ 0.56			$ 1.05			$ 4.79	$ 3.46

Organization, Basis of Presen_6

Organization, Basis of Presentation and Significant Accounting Policies (Details 3) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Disaggregation of Revenue [Line Items]
Management, development and other fees	$ 695	$ 1,017	$ 2,380	$ 2,950
Rental and other income	580,079	566,387	1,691,273	1,742,509
Total revenue	580,774	567,404	1,693,653	1,745,459
Operating Segments | Same Store
Disaggregation of Revenue [Line Items]
Total revenue	519,797	513,418	1,520,420	1,586,405
Operating Segments | Other Stabilized
Disaggregation of Revenue [Line Items]
Total revenue	27,908	22,316	77,034	64,962
Non-allocated
Disaggregation of Revenue [Line Items]
Total revenue	695	419	2,380	1,109
Continuing Operations
Disaggregation of Revenue [Line Items]
Management, development and other fees	3,118	3,094	9,480	8,423
Rental and other income	573,825	539,720	1,655,897	1,660,794
Gain on Business Interruption Insurance Recovery	0	282	0	378
Total revenue	576,943	543,096	1,665,377	1,669,595
Continuing Operations | Management, development and other fees and other ancillary items
Disaggregation of Revenue [Line Items]
Management, development and other fees	695	419	2,380	1,109
Continuing Operations | Rental and non-rental related income
Disaggregation of Revenue [Line Items]
Management, development and other fees	2,423	2,675	7,100	7,314
Continuing Operations | Operating Segments | Same Store
Disaggregation of Revenue [Line Items]
Management, development and other fees	1,883	1,965	5,469	5,447
Rental and other income	517,914	511,171	1,514,951	1,580,580
Gain on Business Interruption Insurance Recovery	0	282	0	378
Total revenue	519,797	513,418	1,520,420	1,586,405
Continuing Operations | Operating Segments | Other Stabilized
Disaggregation of Revenue [Line Items]
Management, development and other fees	369	598	1,148	1,637
Rental and other income	27,539	21,718	75,886	63,325
Gain on Business Interruption Insurance Recovery	0	0	0	0
Total revenue	27,908	22,316	77,034	64,962
Continuing Operations | Operating Segments | Development/ Redevelopment
Disaggregation of Revenue [Line Items]
Management, development and other fees	171	112	483	230
Rental and other income	28,372	6,831	65,060	16,889
Gain on Business Interruption Insurance Recovery	0	0	0	0
Total revenue	28,543	6,943	65,543	17,119
Continuing Operations | Operating Segments | Management, development and other fees and other ancillary items | Same Store
Disaggregation of Revenue [Line Items]
Management, development and other fees	0	0	0	0
Continuing Operations | Operating Segments | Management, development and other fees and other ancillary items | Other Stabilized
Disaggregation of Revenue [Line Items]
Management, development and other fees	0	0	0	0
Continuing Operations | Operating Segments | Management, development and other fees and other ancillary items | Development/ Redevelopment
Disaggregation of Revenue [Line Items]
Management, development and other fees	0	0	0	0
Continuing Operations | Operating Segments | Rental and non-rental related income | Same Store
Disaggregation of Revenue [Line Items]
Management, development and other fees	1,883	1,965	5,469	5,447
Continuing Operations | Operating Segments | Rental and non-rental related income | Other Stabilized
Disaggregation of Revenue [Line Items]
Management, development and other fees	369	598	1,148	1,637
Continuing Operations | Operating Segments | Rental and non-rental related income | Development/ Redevelopment
Disaggregation of Revenue [Line Items]
Management, development and other fees	171	112	483	230
Continuing Operations | Non-allocated
Disaggregation of Revenue [Line Items]
Management, development and other fees	695	419	2,380	1,109
Rental and other income	0	0	0	0
Gain on Business Interruption Insurance Recovery	0	0	0	0
Total revenue	695	419	2,380	1,109
Continuing Operations | Non-allocated | Management, development and other fees and other ancillary items
Disaggregation of Revenue [Line Items]
Management, development and other fees	695	419	2,380	1,109
Continuing Operations | Non-allocated | Rental and non-rental related income
Disaggregation of Revenue [Line Items]
Management, development and other fees	$ 0	$ 0	$ 0	$ 0

Interest Capitalized (Details)

Interest Capitalized (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Interest Capitalized
Capitalized interest during the development and redevelopment of real estate assets	$ 7,862	$ 11,221	$ 25,023	$ 33,738

Mortgage Notes Payable, Unsec_3

Mortgage Notes Payable, Unsecured Notes and Credit Facility (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Notes Payable, Unsecured Notes and Credit Facility
Total mortgage notes payable and unsecured notes and Term Loans	$ 7,844,286	$ 7,629,814
Credit Facility	0	0
Total mortgage notes payable, unsecured notes, Term Loans and Credit Facility	7,844,286	7,629,814
Unsecured notes
Notes Payable, Unsecured Notes and Credit Facility
Long-term Debt, Percentage Bearing Fixed Interest, Amount	6,750,000	6,500,000
Total mortgage notes payable and unsecured notes and Term Loans	7,000,000
Amount of debt discount	9,915	10,380
Amount of deferred financing costs, net	38,448	37,615
Term Loans
Notes Payable, Unsecured Notes and Credit Facility
Variable rate notes	250,000	250,000
Secured notes
Notes Payable, Unsecured Notes and Credit Facility
Long-term Debt, Percentage Bearing Fixed Interest, Amount	379,636	408,964
Variable rate notes	464,650	470,850
Total mortgage notes payable and unsecured notes and Term Loans	547,848
Amount of debt discount	13,806	14,478
Amount of deferred financing costs, net	$ 2,813	$ 3,004

Mortgage Notes Payable, Unsec_4

Mortgage Notes Payable, Unsecured Notes and Credit Facility (Details 2) - USD ($)	1 Months Ended		3 Months Ended		9 Months Ended
	Sep. 30, 2021	Jan. 31, 2021	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Notes Payable, Unsecured Notes and Credit Facility
Repayments of Unsecured Debt					$ 462,147,000	$ 958,681,000
Loss on extinguishment of debt, net			$ (17,890,000)	$ 105,000	(17,768,000)	$ (9,333,000)
Credit Facility	$ 0		0		0		$ 0
Net carrying value of apartment communities and improved land parcels securing debt	1,365,559,000		1,365,559,000		1,365,559,000
Unsecured Notes 2.05 Percent
Notes Payable, Unsecured Notes and Credit Facility
Debt Instrument, Face Amount	700,000,000		$ 700,000,000		$ 700,000,000
Proceeds from Issuance of Debt	694,617,000
Notes Payable Maturities 2021
Notes Payable, Unsecured Notes and Credit Facility
Debt Instrument, Interest Rate, Stated Percentage		5.37%
Notes payable maturing in 2022
Notes Payable, Unsecured Notes and Credit Facility
Loss on extinguishment of debt, net	$ 17,890,000
Notes payable maturing in 2022 | Unsecured notes
Notes Payable, Unsecured Notes and Credit Facility
Debt Instrument, Interest Rate, Stated Percentage	2.95%		2.95%		2.95%
Repayments of Unsecured Debt	$ 450,000,000
Prepayment Penalty	12,147,000
Write off of Deferred Debt Issuance Cost	$ 5,743,000
Unsecured Notes 2.05 Percent | Unsecured notes
Notes Payable, Unsecured Notes and Credit Facility
Debt Instrument, Interest Rate, Stated Percentage	2.05%		2.05%		2.05%
Line of Credit
Notes Payable, Unsecured Notes and Credit Facility
Available borrowing capacity	$ 1,750,000,000		$ 1,750,000,000		$ 1,750,000,000
Annual facility fee, percentage					0.125%
Annual facility fee					$ 2,188,000
Credit Facility	0		0		0		0
Outstanding balance of letters of credit	$ 2,599,000		$ 2,599,000		$ 2,599,000		2,900,000
Line of Credit | LIBOR
Notes Payable, Unsecured Notes and Credit Facility
Debt instrument, basis spread on variable rate (as a percent)					0.775%
Current interest rate (as a percent)	0.86%		0.86%		0.86%
Other Letter of Credit
Notes Payable, Unsecured Notes and Credit Facility
Outstanding balance of letters of credit	$ 37,596,000		$ 37,596,000		$ 37,596,000		$ 32,079,000
Fixed Rate Mortgage Notes Payable
Notes Payable, Unsecured Notes and Credit Facility
Weighted average interest rate, debt (as a percent)	3.80%		3.80%		3.80%		3.80%
Variable Rate Mortgage Notes Payable Unsecured Term Loan and Credit Facility
Notes Payable, Unsecured Notes and Credit Facility
Weighted average interest rate, debt (as a percent)	1.60%		1.60%		1.60%		1.70%
Avalon San Bruno II | Notes Payable Maturities 2021 | Secured Debt
Notes Payable, Unsecured Notes and Credit Facility
Repayments of Secured Debt		$ 27,795,000

Mortgage Notes Payable, Unsec_5

Mortgage Notes Payable, Unsecured Notes and Credit Facility (Details 3) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2021	Jan. 31, 2021	Dec. 31, 2020
Notes Payable, Unsecured Notes and Credit Facility
Mortgage notes payable and unsecured notes	$ 7,844,286		$ 7,629,814
Notes Payable Maturities 2021
Notes Payable, Unsecured Notes and Credit Facility
Stated interest rate of unsecured notes (as a percent)		5.37%
Secured notes
Notes Payable, Unsecured Notes and Credit Facility
Secured notes payments	296,438
Mortgage notes payable and unsecured notes	547,848
Secured notes | Notes Payable Maturities 2021
Notes Payable, Unsecured Notes and Credit Facility
Secured notes payments	1,460
Secured notes | Notes payable maturing in 2022
Notes Payable, Unsecured Notes and Credit Facility
Secured notes payments	9,918
Secured notes | Notes Payable Maturities 2023
Notes Payable, Unsecured Notes and Credit Facility
Secured notes payments	10,739
Secured notes | Notes Payable Maturities 2024
Notes Payable, Unsecured Notes and Credit Facility
Secured notes payments	11,677
Secured notes | Notes Payable Maturities 2025
Notes Payable, Unsecured Notes and Credit Facility
Secured notes payments	12,408
Secured notes | Notes Payable Maturities 2026
Notes Payable, Unsecured Notes and Credit Facility
Secured notes payments	13,445
Secured notes | Notes Payable Maturities 2027
Notes Payable, Unsecured Notes and Credit Facility
Secured notes payments	15,880
Mortgage notes payable and unsecured notes	236,100
Secured notes | Notes Payable Maturities 2028
Notes Payable, Unsecured Notes and Credit Facility
Secured notes payments	20,707
Secured notes | Notes Payable Maturities 2029
Notes Payable, Unsecured Notes and Credit Facility
Secured notes payments	11,742
Mortgage notes payable and unsecured notes	66,250
Secured notes | Notes Payable Maturities 2030
Notes Payable, Unsecured Notes and Credit Facility
Secured notes payments	12,384
Secured notes | Notes Payable Maturities Thereafter
Notes Payable, Unsecured Notes and Credit Facility
Secured notes payments	176,078
Mortgage notes payable and unsecured notes	245,498
Unsecured notes
Notes Payable, Unsecured Notes and Credit Facility
Mortgage notes payable and unsecured notes	$ 7,000,000
Unsecured notes | Notes payable maturing in 2022
Notes Payable, Unsecured Notes and Credit Facility
Stated interest rate of unsecured notes (as a percent)	2.95%
Unsecured notes | Variable Rate Unsecured Term Loan $100 Million
Notes Payable, Unsecured Notes and Credit Facility
Mortgage notes payable and unsecured notes	$ 100,000
Unsecured notes | Variable Rate Unsecured Term Loan $100 Million | LIBOR
Notes Payable, Unsecured Notes and Credit Facility
Debt instrument, basis spread on variable rate (as a percent)	0.90%
Unsecured notes | Notes payable 4.200 Maturities 2023
Notes Payable, Unsecured Notes and Credit Facility
Mortgage notes payable and unsecured notes	$ 350,000
Stated interest rate of unsecured notes (as a percent)	4.20%
Unsecured notes | Notes Payable 2.850 Maturities 2023
Notes Payable, Unsecured Notes and Credit Facility
Mortgage notes payable and unsecured notes	$ 250,000
Stated interest rate of unsecured notes (as a percent)	2.85%
Unsecured notes | Notes Payable Maturities 2024
Notes Payable, Unsecured Notes and Credit Facility
Mortgage notes payable and unsecured notes	$ 300,000
Stated interest rate of unsecured notes (as a percent)	3.50%
Unsecured notes | Variable Rate Unsecured Term Loan $150 Million
Notes Payable, Unsecured Notes and Credit Facility
Mortgage notes payable and unsecured notes	$ 150,000
Unsecured notes | Variable Rate Unsecured Term Loan $150 Million | LIBOR
Notes Payable, Unsecured Notes and Credit Facility
Debt instrument, basis spread on variable rate (as a percent)	0.85%
Unsecured notes | Notes Payable 3.450 Maturities 2025
Notes Payable, Unsecured Notes and Credit Facility
Mortgage notes payable and unsecured notes	$ 525,000
Stated interest rate of unsecured notes (as a percent)	3.45%
Unsecured notes | Notes Payable 3.500 Maturities 2025
Notes Payable, Unsecured Notes and Credit Facility
Mortgage notes payable and unsecured notes	$ 300,000
Stated interest rate of unsecured notes (as a percent)	3.50%
Unsecured notes | Notes Payable 2.950 Maturities 2026
Notes Payable, Unsecured Notes and Credit Facility
Mortgage notes payable and unsecured notes	$ 475,000
Stated interest rate of unsecured notes (as a percent)	2.95%
Unsecured notes | Notes Payable 2.900 Maturities 2026
Notes Payable, Unsecured Notes and Credit Facility
Mortgage notes payable and unsecured notes	$ 300,000
Stated interest rate of unsecured notes (as a percent)	2.90%
Unsecured notes | Notes Payable Maturities 2027
Notes Payable, Unsecured Notes and Credit Facility
Mortgage notes payable and unsecured notes	$ 400,000
Stated interest rate of unsecured notes (as a percent)	3.35%
Unsecured notes | Notes Payable Maturities 2028
Notes Payable, Unsecured Notes and Credit Facility
Mortgage notes payable and unsecured notes	$ 450,000
Stated interest rate of unsecured notes (as a percent)	3.20%
Unsecured notes | Notes Payable Maturities 2029
Notes Payable, Unsecured Notes and Credit Facility
Mortgage notes payable and unsecured notes	$ 450,000
Stated interest rate of unsecured notes (as a percent)	3.30%
Unsecured notes | Notes Payable Maturities 2030
Notes Payable, Unsecured Notes and Credit Facility
Mortgage notes payable and unsecured notes	$ 700,000
Stated interest rate of unsecured notes (as a percent)	2.30%
Unsecured notes | Notes Payable Maturities 2031
Notes Payable, Unsecured Notes and Credit Facility
Mortgage notes payable and unsecured notes	$ 600,000
Stated interest rate of unsecured notes (as a percent)	2.45%
Unsecured notes | Notes Payable Maturities 2032
Notes Payable, Unsecured Notes and Credit Facility
Mortgage notes payable and unsecured notes	$ 700,000
Stated interest rate of unsecured notes (as a percent)	2.05%
Unsecured notes | Notes Payable Maturities 2046
Notes Payable, Unsecured Notes and Credit Facility
Mortgage notes payable and unsecured notes	$ 350,000
Stated interest rate of unsecured notes (as a percent)	3.90%
Unsecured notes | Notes Payable Maturities 2047
Notes Payable, Unsecured Notes and Credit Facility
Mortgage notes payable and unsecured notes	$ 300,000
Stated interest rate of unsecured notes (as a percent)	4.15%
Unsecured notes | Notes Payable Maturities 2048
Notes Payable, Unsecured Notes and Credit Facility
Mortgage notes payable and unsecured notes	$ 300,000
Stated interest rate of unsecured notes (as a percent)	4.35%

Equity (Details)

Equity (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2021	Sep. 30, 2020
Changes in equity
Beginning Balance	$ 10,908,587	$ 10,668,904	$ 10,752,174	$ 10,870,805	$ 10,912,542	$ 10,990,198	$ 10,752,174	$ 10,990,198
Net income attributable to common stockholders	78,914	447,953	142,223	147,703	170,828	167,971	669,090	486,502
Gain (loss) on cash flow hedges	2,010	(822)		1,333	(1,461)	(17,603)	1,188	(17,731)
Cash flow hedge losses reclassified to earnings	7,405	2,366	2,367	2,367	2,301	1,949	12,138	6,617
Change in redemption value of redeemable noncontrolling interest	(261)	(255)	(273)	62	(146)	471
Noncontrolling interest distribution and income allocation	2	(7)	(16)	(17)	1	(35)
Dividends, Common Stock	(222,475)	(222,451)	(221,779)	(222,694)	(224,172)	(224,083)
Issuance of common stock, net of withholdings	4,606	2,496	(13,078)	105	1,188	(14,107)
Stock Repurchased During Period, Value				(137,458)
Amortization of deferred compensation	9,442	10,403	7,286	8,036	9,724	7,781
Ending Balance	$ 10,788,230	$ 10,908,587	$ 10,668,904	$ 10,670,242	$ 10,870,805	$ 10,912,542	10,788,230	10,670,242
Dividends declared to common stockholders (in dollars per share)	$ 1.59	$ 1.59	$ 1.59	$ 1.59	$ 1.59	$ 1.59
Common stock
Changes in equity
Beginning Balance	$ 1,396	$ 1,396	$ 1,395	$ 1,407	$ 1,407	$ 1,406	1,395	1,406
Issuance of common stock, net of withholdings			1			1
Stock Repurchased During Period, Value				(9)
Ending Balance	1,396	1,396	1,396	1,398	1,407	1,407	1,396	1,398
Additional paid-in capital
Changes in equity
Beginning Balance	10,670,564	10,657,665	10,664,416	10,742,796	10,732,022	10,736,733	10,664,416	10,736,733
Issuance of common stock, net of withholdings	4,633	2,496	(14,037)	105	1,050	(12,492)
Stock Repurchased During Period, Value				(69,779)
Amortization of deferred compensation	9,442	10,403	7,286	8,036	9,724	7,781
Ending Balance	10,684,639	10,670,564	10,657,665	10,681,158	10,742,796	10,732,022	10,684,639	10,681,158
Accumulated earnings less dividends
Changes in equity
Beginning Balance	272,398	47,151	126,022	172,304	225,656	282,913	126,022	282,913
Net income attributable to common stockholders	78,914	447,953	142,223	147,703	170,828	167,971
Change in redemption value of redeemable noncontrolling interest	(261)	(255)	(273)	62	(146)	471	(789)	387
Dividends, Common Stock	(222,475)	(222,451)	(221,779)	(222,694)	(224,172)	(224,083)
Issuance of common stock, net of withholdings	(27)		958		138	(1,616)
Stock Repurchased During Period, Value				(67,670)
Ending Balance	128,549	272,398	47,151	29,705	172,304	225,656	128,549	29,705
Accumulated other comprehensive loss
Changes in equity
Beginning Balance	(36,339)	(37,883)	(40,250)	(46,317)	(47,157)	(31,503)	(40,250)	(31,503)
Gain (loss) on cash flow hedges	2,010	(822)		1,333	(1,461)	(17,603)
Cash flow hedge losses reclassified to earnings	7,405	2,366	2,367	2,367	2,301	1,949
Ending Balance	(26,924)	(36,339)	(37,883)	(42,617)	(46,317)	(47,157)	(26,924)	(42,617)
Parent
Changes in equity
Beginning Balance	10,908,019	10,668,329	10,751,583	10,870,190	10,911,928	10,989,549	10,751,583	10,989,549
Net income attributable to common stockholders	78,914	447,953	142,223	147,703	170,828	167,971
Gain (loss) on cash flow hedges	2,010	(822)		1,333	(1,461)	(17,603)
Cash flow hedge losses reclassified to earnings	7,405	2,366	2,367	2,367	2,301	1,949
Change in redemption value of redeemable noncontrolling interest	(261)	(255)	(273)	62	(146)	471
Dividends, Common Stock	(222,475)	(222,451)	(221,779)	(222,694)	(224,172)	(224,083)
Issuance of common stock, net of withholdings	4,606	2,496	(13,078)	105	1,188	(14,107)
Stock Repurchased During Period, Value				(137,458)
Amortization of deferred compensation	9,442	10,403	7,286	8,036	9,724	7,781
Ending Balance	10,787,660	10,908,019	10,668,329	10,669,644	10,870,190	10,911,928	10,787,660	10,669,644
Noncontrolling Interest
Changes in equity
Beginning Balance	568	575	591	615	614	649	591	649
Noncontrolling interest distribution and income allocation	2	(7)	(16)	(17)	1	(35)
Ending Balance	$ 570	$ 568	$ 575	$ 598	$ 615	$ 614	$ 570	$ 598

Equity (Details 2)

Equity (Details 2) - USD ($)	3 Months Ended	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020	Jul. 31, 2020
Class of Stock [Line Items]
Common stock, shares authorized (in shares)	280,000,000	280,000,000		280,000,000
Preferred stock, shares authorized (in shares)	50,000,000	50,000,000		50,000,000
Common stock issued in connection with stock options exercised (in shares)		2,126
Common stock issued through the dividend reinvestment plan (in shares)		2,223	1,967
Number of shares of stock grants withheld (in shares)		75,542	73,103
Common stock issued through Employee Stock Purchase Plan (in shares)		12,145
Stock issued during period, shares, share-based compensation, forfeited (in shares)		3,077
Treasury Stock, Shares, Acquired		0
Stock Repurchase Program, Remaining Authorized Repurchase Amount	$ 316,148,000	$ 316,148,000
Issuance of common stock, net		$ 7,011,000	$ 1,599,000
Amended 2005 Stock Repurchase Program
Class of Stock [Line Items]
Stock Repurchase Program, Authorized Amount					$ 500,000,000
2020 Stock Repurchase Program
Class of Stock [Line Items]
Stock Repurchase Program, Authorized Amount					$ 500,000,000
Continuous Equity Program CEP V
Class of Stock [Line Items]
Common stock sold under CEP V (in shares)	21,000	21,000
Maximum value of shares of common stock that can be sold (in dollars)	$ 1,000,000,000	$ 1,000,000,000
Shares Issued, Weighted Average Price Per Share	$ 227.60	$ 227.60
Issuance of common stock, net	$ 4,708,000	$ 4,708,000
Common stock value, remaining to be authorized under continuous equity program	$ 748,099,000	$ 748,099,000
Maximum | Continuous Equity Program CEP V
Class of Stock [Line Items]
Percentage of compensation received by sales agent		1.50%
Restricted Stock and Restricted Stock Converted From Performance Shares
Class of Stock [Line Items]
Equity instruments granted (in shares)		153,379	165,426

Investments in Real Estate En_3

Investments in Real Estate Entities - Narrative of Investment in Real Estate Entities (Details) ft² in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021USD ($)entityft²	Sep. 30, 2020USD ($)	Sep. 30, 2021USD ($)homeft²communityentity	Sep. 30, 2020USD ($)
Equity method investment
Number of communities acquired | community			4
Payments to Acquire Other Real Estate			$ 392,746	$ 0
Nonoperating expense related to development pursuits	$ (417)	$ (567)	(1,900)	(4,289)
Casualty and impairment loss	1,940	0	3,117	0
Other than Temporary Impairment Losses, Investments	0	0	0	0
Hurricane | East Coast
Equity method investment
Casualty and impairment loss	$ 1,971		1,971
Fire
Equity method investment
Casualty and impairment loss			$ 1,146
AC JV
Equity method investment
Number of Apartment Communities Sold | community			2
Avalon North Point and Avalon North Point Lofts | Notes Payable Maturities 2021 | Secured Debt
Equity method investment
Repayments of Secured Debt			$ 111,653
Avalon Arundel Crossing East
Equity method investment
Number of Apartment Homes Acquired | home			384
Payments to Acquire Other Real Estate			$ 119,000
Avalon Lakeside
Equity method investment
Number of Apartment Homes Acquired | home			425
Payments to Acquire Other Real Estate			$ 117,000
Commercial Square Feet | ft²	18		18
HUB South End
Equity method investment
Number of Apartment Homes Acquired | home			265
Payments to Acquire Other Real Estate			$ 104,350
Commercial Square Feet | ft²	23		23
Three30Five
Equity method investment
Number of Apartment Homes Acquired | home			164
Payments to Acquire Other Real Estate			$ 52,650
The Park Loggia
Equity method investment
Proceeds from Sale of Real Estate	$ 54,277		$ 107,278
Commercial Square Feet | ft²	66		66
Casualty and impairment loss	$ 0	0	$ 0	0
Land Parcel
Equity method investment
Casualty and impairment loss	$ 0	$ 0	$ 0	$ 0
Unconsolidated real estate entities
Equity method investment
Number of unconsolidated real estate entities | entity	8		8
AC JV
Equity method investment
Proceeds from Sale of Real Estate			$ 325,000
AC JV | Avalon North Point and Avalon North Point Lofts
Equity method investment
Number Of Apartment Homes Sold | home			529
Equity Method Investment, Realized Gain (Loss) on Disposal			$ 23,305
Minimum | Unconsolidated real estate entities
Equity method investment
Ownership percentage	20.00%		20.00%
Maximum | Unconsolidated real estate entities
Equity method investment
Ownership percentage	50.00%		50.00%

Investments in Real Estate En_4

Investments in Real Estate Entities - Financial Position and Operating Results (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
ASSETS
Real estate, net	$ 18,366,021		$ 18,366,021		$ 18,233,781
Total assets	19,478,967		19,478,967		19,199,144
LIABILITIES AND EQUITY
Mortgage notes payable, net	827,667		827,667		862,332
Partners' capital	10,787,660		10,787,660		10,751,583
Total liabilities and equity	19,478,967		19,478,967		19,199,144
Combined summary of the operating results of the accounted for using the equity method
Rental and other income	580,774	$ 567,404	1,693,653	$ 1,745,459
Costs and Expenses	(508,374)	(455,887)	(1,445,074)	(1,362,534)
Gains (Losses) on Sales of Investment Real Estate	58	31,607	388,354	91,338
Interest expense, net	(55,987)	(53,249)	(164,704)	(162,562)
Depreciation expense	(193,791)	(175,348)	(561,560)	(529,508)
Net income	78,847	147,717	669,058	486,592
Company's share of net income from investments in unconsolidated entities	7,287	5,611	34,435	8,357
Amortization of excess investment and other	(420)	(528)	(1,476)	(1,587)
Income from investments in unconsolidated entities	6,867	5,083	32,959	6,770
AVA Arts District [Member]
Combined summary of the operating results of the accounted for using the equity method
Long-term Construction Loan	1,032		1,032
Equity Method Investment, Nonconsolidated Investee or Group of Investees
ASSETS
Real estate, net	1,171,955		1,171,955		1,249,730
Other assets	326,339		326,339		255,606
Total assets	1,498,294		1,498,294		1,505,336
LIABILITIES AND EQUITY
Mortgage notes payable, net	636,796		636,796		751,257
Other liabilities	172,660		172,660		163,808
Partners' capital	688,838		688,838		590,271
Total liabilities and equity	1,498,294		1,498,294		$ 1,505,336
Combined summary of the operating results of the accounted for using the equity method
Rental and other income	44,819	28,800	111,562	92,299
Costs and Expenses	(10,698)	(12,782)	(34,992)	(37,034)
Gains (Losses) on Sales of Investment Real Estate	0	18,408	164,317	18,448
Interest expense, net	(6,137)	(8,024)	(21,386)	(24,133)
Depreciation expense	(6,912)	(8,704)	(22,831)	(26,106)
Net income	$ 21,072	$ 17,698	$ 196,670	$ 23,474

Real Estate Disposition Activ_3

Real Estate Disposition Activities (Details) ft² in Thousands	3 Months Ended				9 Months Ended		21 Months Ended
	Sep. 30, 2021USD ($)residential_condominiumft²community	Jun. 30, 2021USD ($)home	Mar. 31, 2021USD ($)home	Sep. 30, 2020USD ($)	Sep. 30, 2021USD ($)residential_condominiumft²community	Sep. 30, 2020USD ($)	Sep. 30, 2021USD ($)residential_condominiumft²community	Dec. 31, 2020USD ($)
Summary of income from discontinued operations
Gains (Losses) on Sales of Investment Real Estate	$ 58,000			$ 31,607,000	$ 388,354,000	$ 91,338,000
Number Of Communities Held For Sale | community	1				1		1
Number of Residential Condominium Units Sold | residential_condominium	17				43		113
Gain (Loss) on Sale of Other Investments					$ 2,051,000	8,174,000
Number of Residential Condominiums Remaining to be Sold | residential_condominium	59				59		59
Other Selling, General and Administrative Expense	$ 1,187,000			$ 1,373,000	$ 3,453,000	$ 4,012,000
For-sale condominium inventory	171,113,000				171,113,000		$ 171,113,000	$ 267,219,000
The Park Loggia
Summary of income from discontinued operations
Proceeds from Sale of Real Estate	$ 54,277,000				$ 107,278,000
Number Of Residential Condominium Units | residential_condominium	172				172		172
Commercial Square Feet | ft²	66				66		66
Gain (Loss) on Sale of Other Investments	$ 1,345,000				$ 2,051,000
eaves Stamford
Summary of income from discontinued operations
Number Of Apartment Homes Sold | home			238
Proceeds from Sale of Real Estate			$ 72,000,000
Gains (Losses) on Sales of Investment Real Estate			$ 53,775,000
Avalon Norwalk
Summary of income from discontinued operations
Number Of Apartment Homes Sold | home		311
Proceeds from Sale of Real Estate		$ 103,000,000
Gains (Losses) on Sales of Investment Real Estate		$ 48,912,000
AVA Cortez Hill
Summary of income from discontinued operations
Number Of Apartment Homes Sold | home		299
Proceeds from Sale of Real Estate		$ 96,500,000
Gains (Losses) on Sales of Investment Real Estate		$ 75,716,000
Avalon Redmond Place
Summary of income from discontinued operations
Number Of Apartment Homes Sold | home		222
Proceeds from Sale of Real Estate		$ 97,700,000
Gains (Losses) on Sales of Investment Real Estate		$ 72,929,000
Avalon Bronxville
Summary of income from discontinued operations
Number Of Apartment Homes Sold | home		110
Proceeds from Sale of Real Estate		$ 89,000,000
Gains (Losses) on Sales of Investment Real Estate		$ 71,773,000
Avalon Glen Cove and Avalon Glen Cove North
Summary of income from discontinued operations
Number Of Apartment Homes Sold | home		367
Proceeds from Sale of Real Estate		$ 126,000,000
Gains (Losses) on Sales of Investment Real Estate		$ 65,242,000

Commitments and Contingencies -

Commitments and Contingencies - Narrative (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021USD ($)propertyLeasecommunity	Sep. 30, 2020USD ($)	Sep. 30, 2021USD ($)propertyLeasecommunity	Sep. 30, 2020USD ($)	Dec. 31, 2020USD ($)
Lessee, Lease, Description [Line Items]
Number Of Office Leases | Lease	13		13
Payments to Acquire Other Real Estate			$ 392,746	$ 0
Operating lease assets	$ 126,699		126,699		$ 133,581
Operating lease obligation	154,790		154,790		161,313
Operating Lease, Expense	3,905	$ 3,958	11,628	$ 12,115
Finance lease asset	25,616		25,616		21,685
Finance lease obligation	20,131		$ 20,131		$ 20,166
Avalon Hackensack at Riverside
Lessee, Lease, Description [Line Items]
Payments to Acquire Other Real Estate	$ 10,336
Properties on Land Subject to Land Leases
Lessee, Lease, Description [Line Items]
Number Of operating apartment communities owned | community	8		8
Number of commercial properties owned | property	2		2
Assets Held under Operating Leases
Lessee, Lease, Description [Line Items]
Number Of operating apartment communities owned | community	7		7
Assets Held under Finance Leases
Lessee, Lease, Description [Line Items]
Number Of operating apartment communities owned | community	1		1
Number Of Finance Leases For Parking Garages Adjacent To Communities | Lease	3		3

Segment Reporting (Details)

Segment Reporting (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Reconciliation of NOI to net income
Net income	$ 78,847	$ 147,717	$ 669,058	$ 486,592
Property management and other indirect operating expenses, net of corporate income	25,322	23,837	74,110	70,043
Other Nonoperating Income (Expense)	417	567	1,900	4,289
Interest Expense	55,987	53,249	164,704	162,562
Loss on extinguishment of debt, net	(17,890)	105	(17,768)	(9,333)
General and administrative expense	17,313	13,985	53,130	46,878
Income from investments in unconsolidated entities	(6,867)	(5,083)	(32,959)	(6,770)
Depreciation expense	193,791	175,348	561,560	529,508
Income tax expense (benefit)	2,179	(27)	1,434	(1,069)
Casualty and impairment loss	1,940	0	3,117	0
Gain on sale of communities	(58)	(31,607)	(388,354)	(91,338)
Gain on other real estate transactions, net	(1,543)	(129)	(2,002)	(328)
Net for-sale condominium activity	(158)	646	1,402	(4,162)
Net operating income from real estate assets sold or held for sale	(2,373)	(14,686)	(17,393)	(47,798)
Net operating income	$ 382,687	$ 363,712	$ 1,107,475	$ 1,157,740
Non-Apartment Components Of Mixed-Use Communities And Other Nonresidential Operations | Operating Income (Loss) | Product Concentration Risk
Segment Reporting Information [Line Items]
Concentration Risk, Percentage	1.80%	1.20%	1.60%	1.10%

Segment Reporting (Details 2)

Segment Reporting (Details 2) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Segment Reporting [Abstract]
Rental income from real estate assets sold or held for sale	$ 3,831	$ 24,308	$ 28,276	$ 75,864
Operating expenses from real estate assets sold or held for sale	(1,458)	(9,622)	(10,883)	(28,066)
Net operating income from real estate assets sold or held for sale	$ 2,373	$ 14,686	$ 17,393	$ 47,798

Segment Reporting (Details 3)

Segment Reporting (Details 3) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Segment Reporting
Total revenue	$ 580,774	$ 567,404	$ 1,693,653	$ 1,745,459
NOI	382,687	363,712	1,107,475	1,157,740
Gross real estate	24,376,310	23,221,488	24,376,310	23,221,488
Real estate assets held for sale, net	89,529		89,529
Operating Segments | Established
Segment Reporting
Total revenue	519,797	513,418	1,520,420	1,586,405
NOI	347,694	347,158	1,023,057	1,108,837
Gross real estate	20,100,815	19,954,294	20,100,815	19,954,294
Operating Segments | Established | New England
Segment Reporting
Total revenue	77,037	75,394	224,614	231,478
NOI	48,115	48,290	142,278	152,589
Gross real estate	2,781,806	2,756,835	2,781,806	2,756,835
Operating Segments | Established | Metro NY/NJ
Segment Reporting
Total revenue	108,776	106,542	319,079	325,807
NOI	72,564	72,283	215,147	225,793
Gross real estate	4,129,121	4,102,402	4,129,121	4,102,402
Operating Segments | Established | Mid-Atlantic
Segment Reporting
Total revenue	85,328	84,974	252,271	261,932
NOI	56,103	56,721	168,359	182,503
Gross real estate	3,575,978	3,550,373	3,575,978	3,550,373
Operating Segments | Established | Southeast Florida
Segment Reporting
Total revenue	8,152	6,950	23,099	21,818
NOI	5,026	3,331	13,772	11,755
Gross real estate	395,594	393,594	395,594	393,594
Operating Segments | Established | Denver, Colorado
Segment Reporting
Total revenue	6,070	5,422	17,576	15,758
NOI	4,011	3,418	11,965	10,084
Gross real estate	320,214	319,038	320,214	319,038
Operating Segments | Established | Pacific Northwest
Segment Reporting
Total revenue	28,092	27,545	81,640	84,808
NOI	19,197	18,913	55,389	59,977
Gross real estate	1,057,166	1,051,451	1,057,166	1,051,451
Operating Segments | Established | Northern California
Segment Reporting
Total revenue	90,127	97,777	270,124	308,522
NOI	63,088	71,207	190,658	232,470
Gross real estate	3,458,280	3,430,831	3,458,280	3,430,831
Operating Segments | Established | Southern California
Segment Reporting
Total revenue	116,215	108,814	332,017	336,282
NOI	79,590	72,995	225,489	233,666
Gross real estate	4,382,656	4,349,770	4,382,656	4,349,770
Operating Segments | Other Stabilized
Segment Reporting
Total revenue	27,908	22,316	77,034	64,962
NOI	18,217	14,238	49,796	42,251
Gross real estate	1,528,196	1,125,829	1,528,196	1,125,829
Operating Segments | Development / Redevelopment
Segment Reporting
Total revenue	28,543	6,943	65,543	17,119
NOI	16,776	2,316	34,622	6,652
Gross real estate	2,401,751	1,698,823	2,401,751	1,698,823
Operating Segments | Disposals
Segment Reporting
Gross real estate		720,432		720,432
Land Held for Future Development
Segment Reporting
Gross real estate	66,769	43,494	66,769	43,494
Non-allocated
Segment Reporting
Total revenue	695	419	2,380	1,109
Gross real estate	278,779	399,048	278,779	399,048
Continuing Operations
Segment Reporting
Total revenue	576,943	543,096	1,665,377	1,669,595
Continuing Operations | Operating Segments | Established
Segment Reporting
Total revenue	519,797	513,418	1,520,420	1,586,405
Continuing Operations | Operating Segments | Other Stabilized
Segment Reporting
Total revenue	27,908	22,316	77,034	64,962
Continuing Operations | Non-allocated
Segment Reporting
Total revenue	$ 695	$ 419	$ 2,380	$ 1,109

Stock-Based Compensation Plan_2

Stock-Based Compensation Plans (Details 2) - $ / shares	9 Months Ended
	Sep. 30, 2021	Dec. 31, 2020
Weighted average grant date fair value per award
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period	(2,126)
Employee and Directors Stock Options
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period	2 years
Share-based Compensation Arrangement by Share-based Payment Award, Expiration Period	10 years
Dividend yield	3.50%
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Volatility Rate	27.10%
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Risk Free Interest Rate	0.81%
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Term	5 years
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value	$ 28.64
Employee and Directors Stock Options | Stock Option and Incentive Plan 2009
Weighted average grant date fair value per award
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number	299,782	12,506
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Number	10,380
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period	(2,126)
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross	294,115
Share-based Compensation Arrangement by Share-based Payment Award, Options, Forfeitures in Period	(4,713)
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price	$ 178.61	$ 129.35
Share-based Compensation Arrangements by Share-based Payment Award, Options, Exercises in Period, Weighted Average Exercise Price	121.78
Share-based Compensation Arrangements by Share-based Payment Award, Options, Grants in Period, Weighted Average Exercise Price	180.32
Share-based Compensation Arrangements by Share-based Payment Award, Options, Forfeitures in Period, Weighted Average Exercise Price	180.32
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Weighted Average Exercise Price	$ 130.90
Performance Options
Weighted average grant date fair value per award
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross	4,847
Performance Shares
Performance awards
Equity instruments outstanding at the beginning of the period (in shares)	241,921
Equity instruments granted (in shares)	138,033
Change in awards based on performance (in shares)	(37,469)
Converted to restricted stock (in shares)	(56,545)
Forfeited (in shares)	(1,418)
Equity instruments outstanding at the end of the period (in shares)	284,522
Weighted average grant date fair value per award
Equity instruments outstanding at the beginning of the period (in dollars per share)	$ 195.13
Grant date fair value per share (in dollars per share)	191.12
Change in awards based on performance (in dollars per share)	156
Converted to restricted stock (in dollars per share)	156
Forfeited (in dollars per share)	207.65
Equity instruments outstanding at the end of the period (in dollars per share)	$ 206.05
Grants in period based on total shareholder metrics	69,064
Grants in period based on financial metrics	68,969
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Dividend yield	3.50%

Stock-Based Compensation Plan_3

Stock-Based Compensation Plans Stock-Based Compensation Plans (Details 3) - Performance Shares	9 Months Ended
	Sep. 30, 2021$ / shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Dividend yield	3.50%
Estimated volatility, Minimum (as a percent)	22.00%
Estimated volatility, Maximum (as a percent)	49.00%
Risk-free interest rate, minimum (as a percent)	0.06%
Risk-free interest rate, maximum (as a percent)	0.38%
Average estimated fair value (in dollars per share)	$ 213.16
Historical volatility (as a percent)	50.00%
Implied volatility (as a percent)	50.00%

Stock-Based Compensation Plan_4

Stock-Based Compensation Plans Stock-Based Compensation Plans (Details 4) - $ / shares	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Restricted stock
Restricted stock shares
Equity instruments outstanding at the beginning of the period (in shares)	131,724
Equity instruments granted (in shares)	96,834	69,109
Vested (in shares)	(68,702)
Forfeited (in shares)	(3,077)
Equity instruments outstanding at the end of the period (in shares)	156,779
Restricted stock shares weighted average grant date fair value per share
Equity instruments outstanding at the beginning of the period (in dollars per share)	$ 203.28
Grant date fair value per share (in dollars per share)	177.49
Vested (in dollars per share)	192.07
Forfeited (in dollars per share)	193.47
Equity instruments outstanding at the end of the period (in dollars per share)	$ 192.45
Restricted Stock Converted From Performance Shares
Restricted stock shares
Equity instruments outstanding at the beginning of the period (in shares)	146,319
Equity instruments granted (in shares)	0	96,317
Vested (in shares)	(71,692)
Forfeited (in shares)	0
Equity instruments outstanding at the end of the period (in shares)	74,627

Stock-Based Compensation Plan_5

Stock-Based Compensation Plans (Details 5) - USD ($) $ / shares in Units, $ in Thousands	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Additional disclosures
Stock-based compensation expense	$ 19,965	$ 17,385
Capitalized stock-based compensation cost	$ 6,899	$ 8,291
Performance Shares
Additional disclosures
Grant date value (in dollars per share)	$ 178.38
Restricted stock and restricted stock units
Additional disclosures
Unrecognized compensation cost	$ 46,683
Weighted average period for recognition of unrecognized compensation cost	1 year 10 months 24 days

Related Party Arrangements (Det

Related Party Arrangements (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Related Party Arrangements
Management, development and other fees	$ 695	$ 1,017	$ 2,380	$ 2,950
Compensation expense			19,965	17,385
Unconsolidated real estate entities
Related Party Arrangements
Outstanding receivables	3,374		3,374		$ 5,408
Non Employee Director | Restricted stock and deferred stock awards
Related Party Arrangements
Compensation expense	516	$ 459	1,457	$ 1,360
Amount of deferred compensation	$ 1,119		$ 1,119		$ 614

Fair Value (Details)

Fair Value (Details)	1 Months Ended	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2021USD ($)derivative	Sep. 30, 2021USD ($)derivative	Mar. 31, 2021USD ($)	Sep. 30, 2021USD ($)derivative	Sep. 30, 2020USD ($)	Dec. 31, 2020USD ($)
Derivative instruments and Hedging Activities
Derivative, Notional Amounts Settled During Period	$ 200,000,000		$ 150,000,000
Receipt (payment) for termination of forward interest rate swaps	$ (2,211,000)		6,962,000	$ 4,751,000	$ (25,135,000)
Unrealized gain on terminated cash flow hedges			$ (2,654,000)	(2,654,000)	$ 0	$ 2,894,000
Interest Rate Swap | Cash Flow Hedges
Derivative instruments and Hedging Activities
Derivative, Notional Amounts Entered Into During Period		$ 150,000,000
Reclassification out of Accumulated Other Comprehensive Income
Derivative instruments and Hedging Activities
Estimated hedging losses to be reclassified from accumulated other comprehensive loss into earnings within the next twelve months				$ 4,051,000
Not Designated as Hedging Instrument
Derivative instruments and Hedging Activities
Number of derivative instruments held | derivative	5	5		5

Fair Value (Details 2)

Fair Value (Details 2) $ in Thousands	Sep. 30, 2021USD ($)
Not Designated as Hedging Instrument | Interest Rate Cap
Derivative instruments and Hedging Activities
Derivative, Notional Amount	$ 410,950
Derivative weighted average interest rate	1.60%
Derivative, average cap interest rate	6.10%
Cash Flow Hedges | Interest Rate Swap
Derivative instruments and Hedging Activities
Derivative, Notional Amount	$ 150,000
Derivative, average cap interest rate	1.40%

Fair Value (Details 3)

Fair Value (Details 3) - USD ($) $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2021	Sep. 30, 2020
Fair Value Disclosures [Abstract]
Cash flow hedge losses reclassified to earnings	$ (7,405)	$ (2,366)	$ (2,367)	$ (2,367)	$ (2,301)	$ (1,949)	$ (12,138)	$ (6,617)

Fair Value (Details 4)

Fair Value (Details 4) - Recurring basis - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Estimate of Fair Value Measurement
Financial Instruments Measured/Discussed at Fair Value
DownREIT units	$ (1,662)	$ (1,203)
Total	(8,296,897)	(8,312,664)
Unsecured notes | Estimate of Fair Value Measurement
Financial Instruments Measured/Discussed at Fair Value
Indebtedness	(7,280,382)	(7,271,799)
Secured Debt and Variable Rate Unsecured Indebtedness | Estimate of Fair Value Measurement
Financial Instruments Measured/Discussed at Fair Value
Indebtedness	(1,018,373)	(1,043,976)
Interest Rate Cap | Not Designated as Hedging Instrument | Estimate of Fair Value Measurement
Financial Instruments Measured/Discussed at Fair Value
Derivative assets	121	6
Interest Rate Swap | Cash Flow Hedges | Estimate of Fair Value Measurement
Financial Instruments Measured/Discussed at Fair Value
Derivative assets	3,399	4,308
Fair Value, Inputs, Level 1
Financial Instruments Measured/Discussed at Fair Value
DownREIT units	(1,662)	(1,203)
Total	(7,282,044)	(7,273,002)
Fair Value, Inputs, Level 1 | Unsecured notes
Financial Instruments Measured/Discussed at Fair Value
Indebtedness	(7,280,382)	(7,271,799)
Fair Value, Inputs, Level 2
Financial Instruments Measured/Discussed at Fair Value
Total	(1,014,853)	(1,039,662)
Fair Value, Inputs, Level 2 | Secured Debt and Variable Rate Unsecured Indebtedness
Financial Instruments Measured/Discussed at Fair Value
Indebtedness	(1,018,373)	(1,043,976)
Fair Value, Inputs, Level 2 | Interest Rate Cap | Not Designated as Hedging Instrument
Financial Instruments Measured/Discussed at Fair Value
Derivative assets	121	6
Fair Value, Inputs, Level 2 | Interest Rate Swap | Cash Flow Hedges
Financial Instruments Measured/Discussed at Fair Value
Derivative assets	3,399	4,308
Fair Value, Inputs, Level 3
Financial Instruments Measured/Discussed at Fair Value
Total	$ 0	$ 0

Subsequent Events (Details)

Subsequent Events (Details)	Nov. 04, 2021USD ($)	Oct. 31, 2021USD ($)home$ / sharesshares	Sep. 30, 2021USD ($)$ / sharesshares	Sep. 30, 2021USD ($)$ / sharesshares	Sep. 30, 2020USD ($)	Dec. 31, 2020USD ($)
Subsequent Event [Line Items]
Payments to Acquire Other Real Estate				$ 392,746,000	$ 0
Issuance of common stock, net				7,011,000	$ 1,599,000
Credit Facility			$ 0	0		$ 0
Line of Credit
Subsequent Event [Line Items]
Credit Facility			$ 0	$ 0		$ 0
Continuous Equity Program CEP V
Subsequent Event [Line Items]
Common stock sold under CEP V (in shares) | shares			21,000	21,000
Shares Issued, Weighted Average Price Per Share | $ / shares			$ 227.60	$ 227.60
Issuance of common stock, net			$ 4,708,000	$ 4,708,000
Subsequent Event [Member] | Notes Payable Maturities 2036, Fixed Rate | Secured Debt
Subsequent Event [Line Items]
Repayments of Secured Debt	$ 73,060,000
Weighted average interest rate, debt (as a percent)	3.79%
Subsequent Event [Member] | Line of Credit
Subsequent Event [Line Items]
Credit Facility	$ 39,000,000
Subsequent Event [Member] | Continuous Equity Program CEP V
Subsequent Event [Line Items]
Common stock sold under CEP V (in shares) | shares		101,343
Shares Issued, Weighted Average Price Per Share | $ / shares		$ 225.85
Issuance of common stock, net		$ 22,545,000
Subsequent Event [Member] | Curv
Subsequent Event [Line Items]
Number of Apartment Homes Acquired | home		243
Commercial Square Feet | home		49,000
Percent of Commercial Square Feet Leased		100.00%
Payments to Acquire Other Real Estate		$ 150,000,000