AvalonBay Communities (AVB) 10-Q 4 Aug 21 2021 Q2 Quarterly report Financial data

Cover Page

Cover Page - shares	6 Months Ended
	Jun. 30, 2021	Jul. 31, 2021
Cover [Abstract]
Document Type	10-Q
Document Period End Date	Jun. 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		139,616,764
Entity Central Index Key	0000915912
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	Q2
Amendment Flag	false
Document Quarterly Report	true
Document Transition Report	false

CONDENSED CONSOLIDATED BALANCE

CONDENSED CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Real estate:
Land and improvements	$ 4,442,708	$ 4,394,298
Buildings and improvements	17,549,286	17,231,275
Furniture, fixtures and equipment	965,741	924,583
Gross operating real estate	22,957,735	22,550,156
Less accumulated depreciation	(5,907,270)	(5,700,179)
Net operating real estate	17,050,465	16,849,977
Construction in Progress, Gross	773,938	989,765
Land held for development	100,106	110,142
For-sale condominium inventory	220,022	267,219
Real estate assets held for sale, net	0	16,678
Real Estate Investment Property, Net, Total	18,144,531	18,233,781
Cash and cash equivalents	297,036	216,976
Cash in escrow	190,069	96,556
Resident security deposits	32,350	30,811
Investments in unconsolidated real estate entities	227,953	202,612
Deferred development costs	49,335	55,427
Prepaid expenses and other assets	220,916	207,715
Right of use lease assets	154,435	155,266
Total assets	19,316,625	19,199,144
LIABILITIES AND EQUITY
Unsecured notes, net	6,705,513	6,702,005
Variable rate unsecured credit facility	0	0
Mortgage notes payable, net	828,120	862,332
Dividends payable	224,282	224,897
Payables for construction	66,315	93,609
Accrued expenses and other liabilities	295,771	274,699
Lease liabilities	177,448	181,479
Accrued interest payable	48,974	49,033
Resident security deposits	58,576	55,928
Liabilities related to real estate assets held for sale	0	311
Total liabilities	8,404,999	8,444,293
Commitments and contingencies
Redeemable noncontrolling interests	3,039	2,677
Equity:
Preferred Stock, Value, Issued	0	0
Common Stock, Value, Issued	1,396	1,395
Additional paid-in capital	10,670,564	10,664,416
Accumulated earnings less dividends	272,398	126,022
Accumulated other comprehensive loss	(36,339)	(40,250)
Stockholders' Equity Attributable to Parent	10,908,019	10,751,583
Stockholders' Equity Attributable to Noncontrolling Interest	568	591
Total equity	10,908,587	10,752,174
Total liabilities and equity	$ 19,316,625	$ 19,199,144

CONDENSED CONSOLIDATED BALANC_2

CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) - $ / shares	Jun. 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)	139,618,254	139,526,671
Common stock, shares outstanding (in shares)	139,618,254	139,526,671

CONDENSED CONSOLIDATED STATEMEN

CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Revenue:
Rental and other income	$ 560,935	$ 575,479	$ 1,111,194	$ 1,176,123
Management, development and other fees	808	926	1,685	1,933
Total revenue	561,743	576,405	1,112,879	1,178,056
Expenses:
Operating expenses, excluding property taxes	141,622	131,090	281,673	263,083
Property taxes	70,776	67,013	140,186	134,039
Other Nonoperating Income (Expense)	1,653	388	1,483	3,722
Interest Expense	56,104	53,399	108,717	109,313
Gain (Loss) on Extinguishment of Debt	0	268	(122)	9,438
Depreciation expense	184,472	176,249	367,769	354,160
General and administrative expense	18,465	15,573	35,817	32,893
Casualty and impairment loss	1,177	0	1,177	0
Total expenses	474,269	443,980	936,700	906,648
Income from investments in unconsolidated entities	26,559	512	26,092	1,687
Gains (Losses) on Sales of Investment Real Estate	334,569	35,295	388,296	59,731
Gain on other real estate transactions, net	32	156	459	199
Net for-sale condominium activity	(647)	1,348	(1,560)	4,808
Income before income taxes	447,987	169,736	589,466	337,833
Income tax (expense) benefit	(10)	1,133	745	1,042
Net income	447,977	170,869	590,211	338,875
Net income attributable to noncontrolling interests	(24)	(41)	(35)	(76)
Net income attributable to common stockholders	447,953	170,828	590,176	338,799
Other comprehensive income:
Loss on cash flow hedges	(822)	(1,461)	(822)	(19,064)
Cash flow hedge losses reclassified to earnings	2,366	2,301	4,733	4,250
Comprehensive income	$ 449,497	$ 171,668	$ 594,087	$ 323,985
Earnings per common share - basic:
Net income attributable to common stockholders (in dollars per share)	$ 3.21	$ 1.21	$ 4.23	$ 2.41
Earnings per common share - diluted:
Net income attributable to common stockholders (in dollars per share)	$ 3.21	$ 1.21	$ 4.23	$ 2.41

CONDENSED CONSOLIDATED STATEM_2

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Cash flows from operating activities:
Net income	$ 447,977	$ 170,869	$ 590,211	$ 338,875
Adjustments to reconcile net income to cash provided by operating activities:
Depreciation expense	184,472	176,249	367,769	354,160
Amortization of deferred financing costs			3,675	3,720
Amortization of debt discount			1,320	833
(Gain) loss on extinguishment of debt, net	0	(268)	122	(9,438)
Amortization of stock-based compensation			13,185	11,870
Equity in loss of, and return on, unconsolidated real estate entities and noncontrolling interests, net of eliminations			2,989	3,705
Real estate casualty loss			831	0
Abandonment of development pursuits			685	2,095
Unrealized gain on terminated cash flow hedges			(2,654)	0	$ 2,894
Cash flow hedge losses reclassified to earnings			4,733	4,250
Gain on sale of real estate assets			(412,060)	(59,930)
Gain on for-sale condominiums			(706)	(7,446)
Increase in resident security deposits, prepaid expenses and other assets			(16,329)	(13,595)
Increase in accrued expenses, other liabilities and accrued interest payable			15,102	(19,058)
Net cash provided by operating activities			568,629	628,917
Cash flows from investing activities:
Payments to Develop Real Estate Assets			(325,692)	(383,139)
Development/redevelopment of real estate assets including land acquisitions and deferred development costs			(118,572)	0
Capital expenditures - existing real estate assets			(57,157)	(51,858)
Capital expenditures - non-real estate assets			(2,584)	(14,461)
Decrease in payables for construction			(27,294)	(11,547)
Proceeds from sale of real estate, net of selling costs			575,431	132,882
Proceeds from the sale of for-sale condominiums, net of selling costs			48,655	155,217
Mortgage note receivable lending			(113)	(209)
Mortgage note receivable payments			1,556	2,238
Distributions from unconsolidated real estate entities			22,331	0
Investments in unconsolidated real estate entities			(27,356)	(14,251)
Net cash provided by (used in) investing activities			89,205	(185,128)
Cash flows from financing activities:
Issuance of common stock, net			2,372	1,613
Dividends paid			(444,572)	(437,326)
Issuance of mortgage notes payable			0	51,000
Repayments of mortgage notes payable, including prepayment penalties			(34,734)	(56,852)
Issuance of unsecured notes			0	1,296,581
Repayment of unsecured notes, including prepayment penalties			0	(958,680)
Payment of deferred financing costs			0	(11,276)
Receipt (payment) for termination of forward interest rate swaps			6,962	(25,135)
Payment to noncontrolling interest			(33)	(42)
Payments related to tax withholding for share-based compensation			(13,228)	(14,750)
Distributions to DownREIT partnership unitholders			(24)	(24)
Distributions to joint venture and profit-sharing partners			(164)	(218)
Preferred interest obligation redemption and dividends			(840)	(600)
Net cash used in financing activities			(484,261)	(155,709)
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect, Total			173,573	288,080
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Beginning Balance			313,532	127,614	127,614
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Ending Balance	487,105	415,694	487,105	415,694	313,532
Cash paid during the period for interest, net of amount capitalized			101,703	103,328
Supplemental Cash Flow Information [Abstract]
Cash and cash equivalents	297,036	322,817	297,036	322,817	216,976
Cash in escrow	190,069	92,877	190,069	92,877	96,556
Cash, cash equivalents and cash in escrow reported in the Condensed Consolidated Statements of Cash Flows	$ 487,105	$ 415,694	$ 487,105	$ 415,694	$ 313,532

CONDENSED CONSOLIDATED STATEM_3

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Parenthetical) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2020USD ($)Lease	Jun. 30, 2021USD ($)shares	Jun. 30, 2020USD ($)Leaseshares
Supplemental disclosures of non-cash investing and financing activities
Common stock issued through the dividend reinvestment plan (in shares) | shares		1,561	1,183
Common stock issued through the dividend reinvestment plan		$ 274	$ 217
Number of shares withheld to satisfy employees' tax withholding and other liabilities (in shares) | shares		74,726	73,089
Shares withheld to satisfy employees' tax withholding and other liabilities, value		$ 13,228	$ 14,750
Stock issued during period, shares, share-based compensation, forfeited (in shares) | shares		709
Stock issued during period, value, share-based compensation, forfeited		$ 140	685
Dividends declared but not paid		224,282
Change in redemption value of redeemable noncontrolling interest	$ (146)
Cash flow hedge losses reclassified to earnings	2,301	4,733	4,250
Operating Lease, Right-of-Use Asset		129,064
Total lease liabilities		157,305
Increase (Decrease) in Derivative Liabilities		$ (822)	98
Increase (Decrease) in Derivative Assets			$ 178
Restricted Stock and Restricted Stock Converted From Performance Shares
Supplemental disclosures of non-cash investing and financing activities
Equity instruments granted (in shares) | shares		151,186	164,526
Restricted Stock Converted From Performance Shares
Supplemental disclosures of non-cash investing and financing activities
Equity instruments granted (in shares) | shares		0	96,317
Restricted stock
Supplemental disclosures of non-cash investing and financing activities
Equity instruments granted (in shares) | shares		94,641	68,209
Fair value of shares issued		$ 16,687	$ 15,150
Stock issued during period, shares, share-based compensation, forfeited (in shares) | shares		709	4,050
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
Common stock
Supplemental disclosures of non-cash investing and financing activities
Dividends declared but not paid	224,482	$ 222,901	$ 224,482
Accumulated earnings less dividends
Supplemental disclosures of non-cash investing and financing activities
Change in redemption value of redeemable noncontrolling interest	(146)	$ (528)	325
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	6 Months Ended
	Jun. 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 (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, Southeast Florida, Denver, Colorado, the Pacific Northwest, and Northern and Southern California. The Company is pursuing opportunities in new expansion markets of Dallas and Austin, Texas, and Charlotte and Raleigh-Durham, North Carolina. At June 30, 2021, the Company owned or held a direct or indirect ownership interest in 272 operating apartment communities containing 80,958 apartment homes in 11 states and the District of Columbia. In addition, the Company owned or held a direct or indirect ownership interest in 16 communities under development that are expected to contain an aggregate of 4,791 apartment homes when completed, as well as The Park Loggia, which contains 172 for-sale residential condominiums, of which 96 have been sold as of June 30, 2021, and 66,000 square feet of commercial space, of which 87% has been leased as of June 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 23 communities that, if developed as expected, will contain an estimated 7,802 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 six months ended June 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 six months ended 6/30/2021 6/30/2020 6/30/2021 6/30/2020 Basic and diluted shares outstanding Weighted average common shares - basic 139,373,963 140,450,744 139,332,575 140,413,857 Weighted average DownREIT units outstanding 7,500 7,500 7,500 7,500 Effect of dilutive securities 269,176 279,916 261,451 330,974 Weighted average common shares - diluted 139,650,639 140,738,160 139,601,526 140,752,331 Calculation of Earnings per Share - basic Net income attributable to common stockholders $ 447,953 $ 170,828 $ 590,176 $ 338,799 Net income allocated to unvested restricted shares (902) (390) (1,267) (817) Net income attributable to common stockholders, adjusted $ 447,051 $ 170,438 $ 588,909 $ 337,982 Weighted average common shares - basic 139,373,963 140,450,744 139,332,575 140,413,857 Earnings per common share - basic $ 3.21 $ 1.21 $ 4.23 $ 2.41 Calculation of Earnings per Share - diluted Net income attributable to common stockholders $ 447,953 $ 170,828 $ 590,176 $ 338,799 Add: noncontrolling interests of DownREIT unitholders in consolidated partnerships 12 12 24 24 Adjusted net income attributable to common stockholders $ 447,965 $ 170,840 $ 590,200 $ 338,823 Weighted average common shares - diluted 139,650,639 140,738,160 139,601,526 140,752,331 Earnings per common share - diluted $ 3.21 $ 1.21 $ 4.23 $ 2.41 Certain options to purchase shares of common stock in the amount of 292,544 were outstanding as of June 30, 2021, but were not included in the computation of diluted earnings per share because such options were anti-dilutive for the period. All options to purchase shares of common stock outstanding as of June 30, 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 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. 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) that 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 six months ended June 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 June 30, 2021, or otherwise qualify as held for sale as of June 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 June 30, 2021 Management, development and other fees and other ancillary items $ — $ — $ — $ 808 $ 808 Rental and non-rental related income (2) 1,922 395 186 — 2,503 Total non-lease revenue (3) 1,922 395 186 808 3,311 Lease income (4) 498,719 29,104 22,890 — 550,713 Business interruption insurance proceeds — — — — — Total revenue $ 500,641 $ 29,499 $ 23,076 $ 808 $ 554,024 For the period ended June 30, 2020 Management, development and other fees and other ancillary items $ — $ — $ — $ 299 $ 299 Rental and non-rental related income (2) 1,848 482 78 — 2,408 Total non-lease revenue (3) 1,848 482 78 299 2,707 Lease income (4) 520,753 24,160 7,290 — 552,203 Business interruption insurance proceeds 96 — — — 96 Total revenue $ 522,697 $ 24,642 $ 7,368 $ 299 $ 555,006 For the six months ended Same Store Other Development/ Non- Total For the period ended June 30, 2021 Management, development and other fees and other ancillary items $ — $ — $ — $ 1,685 $ 1,685 Rental and non-rental related income (2) 3,571 821 327 — 4,719 Total non-lease revenue (3) 3,571 821 327 1,685 6,404 Lease income (4) 993,569 55,443 40,156 — 1,089,168 Business interruption insurance proceeds — — — — — Total revenue $ 997,140 $ 56,264 $ 40,483 $ 1,685 $ 1,095,572 For the period ended June 30, 2020 Management, development and other fees and other ancillary items $ — $ — $ — $ 690 $ 690 Rental and non-rental related income (2) 3,462 1,073 137 — 4,672 Total non-lease revenue (3) 3,462 1,073 137 690 5,362 Lease income (4) 1,065,425 48,600 14,044 — 1,128,069 Business interruption insurance proceeds 96 — — — 96 Total revenue $ 1,068,983 $ 49,673 $ 14,181 $ 690 $ 1,133,527 __________________________________ (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. (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 June 30, 2021. Lease Revenue Reserves The Company assesses the collectability of its lease revenue and receivables on an on-going basis. Under ASC 842, Lease Accounting, 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 (i) the duration and severity of the pandemic, (ii) the effectiveness of vaccines and the rate of vaccinations, (iii) the duration and nature of governmental responses to contain the spread of the disease and assist consumers and businesses, (iv) consumer and business responses to the pandemic, including preferences for where and how to live and work, and (v) how quickly and to what extent normal economic and operating conditions can resume. Because of this uncertainty, any estimate of the expected impact of the COVID-19 pandemic on results of operations, cash flows, financial condition, or liquidity for periods beyond the six months ended June 30, 2021 is uncertain. As of June 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 $15,065,000 and $20,099,000 for the three months ended June 30, 2021 and 2020, respectively, and $33,710,000 and $24,279,000 for six months ended June 30, 2021 and 2020, respectively, under ASC 842 and ASC 450.

Interest Capitalized

Interest Capitalized	6 Months Ended
	Jun. 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 $8,362,000 and $11,019,000 for the three months ended June 30, 2021 and 2020, respectively, and $17,161,000 and $22,517,000 for the six months ended June 30, 2021 and 2020, respectively.

Mortgage Notes Payable, Unsecur

Mortgage Notes Payable, Unsecured Notes and Credit Facility	6 Months Ended
	Jun. 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 June 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 June 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"). 6/30/2021 12/31/2020 Fixed rate unsecured notes (1) $ 6,500,000 $ 6,500,000 Term Loans (1) 250,000 250,000 Fixed rate mortgage notes payable - conventional and tax-exempt (2) 380,030 408,964 Variable rate mortgage notes payable - conventional and tax-exempt (2) 465,050 470,850 Total mortgage notes payable and unsecured notes and Term Loans 7,595,080 7,629,814 Credit Facility — — Total mortgage notes payable, unsecured notes, Term Loans and Credit Facility $ 7,595,080 $ 7,629,814 _____________________________________ (1) Balances at June 30, 2021 and December 31, 2020 exclude $9,577 and $10,380, respectively, of debt discount, and $34,910 and $37,615, respectively, of deferred financing costs, as reflected in unsecured notes, net on the accompanying Condensed Consolidated Balance Sheets. (2) Balances at June 30, 2021 and December 31, 2020 exclude $14,083 and $14,478, respectively, of debt discount, and $2,877 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 six months ended June 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. At June 30, 2021, the Company has 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 (0.88% at June 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 June 30, 2021 and December 31, 2020, respectively. In addition, the Company had $36,682,000 and $32,079,000 outstanding in additional letters of credit unrelated to the Credit Facility as of June 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 $1,373,062,000, excluding communities classified as held for sale, as of June 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 June 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 June 30, 2021 and December 31, 2020, respectively. Scheduled payments and maturities of secured notes payable and unsecured notes outstanding at June 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 $ 2,414 $ — $ — N/A 2022 9,918 — 450,000 2.950 % 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 176,078 245,338 600,000 2.450 % 350,000 3.900 % 300,000 4.150 % 300,000 4.350 % $ 297,392 $ 547,688 $ 6,750,000 The Company was in compliance at June 30, 2021 with customary financial covenants under the Credit Facility, the Term Loans and the Company's fixed rate unsecured notes.

Equity

Equity	6 Months Ended
	Jun. 30, 2021
Stockholders' Equity Note [Abstract]
Equity	Equity The following summarizes the changes in equity for the six months ended June 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 The following summarizes the changes in equity for the six months ended June 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 As of June 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 six months ended June 30, 2021, the Company: i. issued 2,126 shares of common stock in connection with stock options exercised; ii. issued 1,561 common shares through the Company's dividend reinvestment plan; iii. issued 151,186 common shares in connection with restricted stock grants and the conversion of performance awards to restricted shares; iv. withheld 74,726 common shares to satisfy employees' tax withholding and other liabilities; v. issued 12,145 common shares through the Employee Stock Purchase Plan; and vi. canceled 709 common shares of restricted stock upon forfeiture. Any deferred compensation related to the Company's stock option, restricted stock and performance award grants as of June 30, 2021 is not reflected on the accompanying Condensed Consolidated Balance Sheets as of June 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 six months ended June 30, 2021, the Company had no repurchases of shares under this program. As of June 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 six months ended June 30, 2021, the Company had no sales under the program. As of June 30, 2021, the Company had $752,878,000 remaining authorized for issuance under CEP V.

Investments in Real Estate Enti

Investments in Real Estate Entities	6 Months Ended
	Jun. 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 June 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. 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 three and six months ended June 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 discussed above as of the dates presented, including development joint ventures started and unconsolidated communities sold during the respective periods (dollars in thousands): 6/30/2021 12/31/2020 (unaudited) Assets: Real estate, net $ 1,147,860 $ 1,249,730 Other assets 473,193 255,606 Total assets $ 1,621,053 $ 1,505,336 Liabilities and partners' capital: Mortgage notes payable, net (1) $ 637,676 $ 751,257 Other liabilities 169,258 163,808 Partners' capital 814,119 590,271 Total liabilities and partners' capital $ 1,621,053 $ 1,505,336 _________________________________ (1) The Company has not guaranteed the 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 six months ended 6/30/2021 6/30/2020 6/30/2021 6/30/2020 (unaudited) (unaudited) Rental and other income (1) $ 41,809 $ 30,427 $ 66,744 $ 63,499 Operating and other expenses (12,126) (11,732) (24,293) (23,912) Gain on sale of communities 164,317 40 164,317 40 Interest expense, net (7,582) (8,053) (15,250) (16,109) Depreciation expense (7,441) (8,713) (15,919) (17,402) Net income $ 178,977 $ 1,969 $ 175,599 $ 6,116 Company's share of net income from investments in unconsolidated entities $ 27,087 $ 1,041 $ 27,149 $ 2,746 Amortization of excess investment and other (528) (529) (1,057) (1,059) Income from investments in unconsolidated entities $ 26,559 $ 512 $ 26,092 $ 1,687 _________________________________ (1) Includes unrealized gains on property technology investments during the three and six months ended June 30, 2021. Investments in Consolidated Real Estate Entities During the six months ended June 30, 2021, the Company acquired 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 Company accounted for this purchase as an asset acquisition 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 co sts 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 six months ended June 30, 2021 and 2020, were $1,653,000 and $1,483,000 and $388,000 and $3,722,000, 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 six months ended June 30, 2021 and 2020, other than those related to casualty losses from property damage. During the three and six months ended June 30, 2021, the Company recognized a casualty loss of $1,177,000 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 six months ended June 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 six months ended June 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 six months ended June 30, 2021 and 2020.

Real Estate Disposition Activit

Real Estate Disposition Activities	6 Months Ended
	Jun. 30, 2021
Discontinued Operations and Disposal Groups [Abstract]
Real Estate Disposition Activities	Real Estate Disposition Activities The following real estate sales occurred during the six months ended June 30, 2021: Community Name Location Period of sale Apartment homes Gross sales price Gain on Disposition (1) 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 June 30, 2021, the Company had no real estate assets 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 six months ended June 30, 2021, the Company sold 16 and 26 residential condominiums at The Park Loggia, for gross proceeds of $38,392,000 and $53,001,000, respectively, resulting in a gain in accordance with GAAP of $575,000 and $706,000, respectively. As of June 30, 2021, there were 76 residential condominiums remaining to be sold. The Company incurred $1,222,000 and $1,196,000 during the three months ended June 30, 2021 and 2020, respectively, and $2,266,000 and $2,639,000 during the six months ended June 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 June 30, 2021 and December 31, 2020, the unsold for-sale residential condominiums at The Park Loggia have an aggregate carrying value of $220,022,000 and $267,219,000, respectively, presented as for-sale condominium inventory on the accompanying Condensed Consolidated Balance Sheets.

Commitments and Contingencies

Commitments and Contingencies	6 Months Ended
	Jun. 30, 2021
Leases [Abstract]
Commitments and Contingencies	Commitments and Contingencies Lease Obligations The Company owns nine apartment communities and two commercial properties, located on land subject to ground leases expiring between May 2041 and March 2142. The Company has purchase options for all ground leases expiring prior to 2060. The ground leases for eight of the nine 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. As of June 30, 2021 and December 31, 2020, the Company has total operating lease assets of $129,064,000 and $133,581,000, respectively, and lease obligations of $157,305,000 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 $3,896,000 and $4,240,000 for the three months ended June 30, 2021 and 2020, respectively, and $7,723,000 and $8,157,000 for the six months ended June 30, 2021 and 2020, respectively, related to operating leases. The Company has one apartment community located on land subject to a ground lease and three leases for portions of parking garages, adjacent to apartment communities, that are finance leases. As of June 30, 2021 and December 31, 2020, the Company has total finance lease assets of $25,371,000 and $21,685,000, respectively, and total finance lease obligations of $20,143,000 and $20,166,000, respectively, reported as components of right of use lease assets and lease liabilities, respectively, on the accompanying Condensed Consolidated Balance Sheets.
Commitments and Contingencies	Commitments and Contingencies Lease Obligations The Company owns nine apartment communities and two commercial properties, located on land subject to ground leases expiring between May 2041 and March 2142. The Company has purchase options for all ground leases expiring prior to 2060. The ground leases for eight of the nine 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. As of June 30, 2021 and December 31, 2020, the Company has total operating lease assets of $129,064,000 and $133,581,000, respectively, and lease obligations of $157,305,000 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 $3,896,000 and $4,240,000 for the three months ended June 30, 2021 and 2020, respectively, and $7,723,000 and $8,157,000 for the six months ended June 30, 2021 and 2020, respectively, related to operating leases. The Company has one apartment community located on land subject to a ground lease and three leases for portions of parking garages, adjacent to apartment communities, that are finance leases. As of June 30, 2021 and December 31, 2020, the Company has total finance lease assets of $25,371,000 and $21,685,000, respectively, and total finance lease obligations of $20,143,000 and $20,166,000, respectively, reported as components of right of use lease assets and lease liabilities, respectively, on the accompanying Condensed Consolidated Balance Sheets.

Segment Reporting

Segment Reporting	6 Months Ended
	Jun. 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 for purposes of assessing each segment's performance. The Company's chief operating decision maker ("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, (gain) loss on extinguishment of debt, net, general and administrative expense, income from investments in unconsolidated entities, depreciation expense, corporate income tax (benefit) expense, casualty and impairment (gain) loss, net, gain on sale of communities, (gain) loss 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 1.5% and 0.5% of total NOI for the three months ended June 30, 2021 and 2020, respectively, and 1.5% and 1.1% for the six months ended June 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 six months ended June 30, 2021 and 2020 is as follows (dollars in thousands): For the three months ended For the six months ended 6/30/2021 6/30/2020 6/30/2021 6/30/2020 Net income $ 447,977 $ 170,869 $ 590,211 $ 338,875 Indirect operating expenses, net of corporate income 24,318 23,407 48,788 46,206 Expensed transaction, development and other pursuit costs, net of recoveries 1,653 388 1,483 3,722 Interest expense, net 56,104 53,399 108,717 109,313 Loss (gain) on extinguishment of debt, net — 268 (122) 9,438 General and administrative expense 18,465 15,573 35,817 32,893 Income from investments in unconsolidated entities (26,559) (512) (26,092) (1,687) Depreciation expense 184,472 176,249 367,769 354,160 Income tax expense (benefit) 10 (1,133) (745) (1,042) Casualty and impairment loss 1,177 — 1,177 — Gain on sale of communities (334,569) (35,295) (388,296) (59,731) Gain on other real estate transactions, net (32) (156) (459) (199) Net for-sale condominium activity 647 (1,348) 1,560 (4,808) Net operating income from real estate assets sold or held for sale (4,749) (13,581) (10,549) (28,572) Net operating income $ 368,914 $ 388,128 $ 729,259 $ 798,568 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 six months ended 6/30/2021 6/30/2020 6/30/2021 6/30/2020 Rental income from real estate assets sold or held for sale $ 7,719 $ 21,399 $ 17,307 $ 44,529 Operating expenses from real estate assets sold or held for sale (2,970) (7,818) (6,758) (15,957) Net operating income from real estate assets sold or held for sale $ 4,749 $ 13,581 $ 10,549 $ 28,572 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 six months ended June 30, 2021 and 2020 has been adjusted to exclude the real estate assets that were sold from January 1, 2020 through June 30, 2021, or otherwise qualify as held for sale as of June 30, 2021, as described in Note 6, "Real Estate Disposition Activities." For the three months ended For the six months ended Total NOI Total NOI Gross real estate (1) For the period ended June 30, 2021 Same Store New England $ 74,259 $ 47,895 $ 147,577 $ 94,163 $ 2,772,638 Metro NY/NJ 105,355 70,944 210,304 142,584 4,114,155 Mid-Atlantic 82,232 54,823 163,460 110,083 3,485,698 Southeast Florida 7,706 4,557 14,948 8,746 395,009 Denver, CO 5,853 3,935 11,505 7,954 319,994 Pacific Northwest 26,935 18,298 53,548 36,192 1,054,701 Northern California 89,591 63,506 179,997 127,569 3,450,054 Southern California 108,710 73,364 215,801 145,899 4,373,247 Total Same Store 500,641 337,322 997,140 673,190 19,965,496 Other Stabilized 29,499 19,123 56,264 36,049 1,338,844 Development / Redevelopment 23,076 12,469 40,483 20,020 2,324,779 Land Held for Development N/A N/A N/A N/A 100,106 Non-allocated (2) 808 N/A 1,685 N/A 322,576 Total $ 554,024 $ 368,914 $ 1,095,572 $ 729,259 $ 24,051,801 For the period ended June 30, 2020 Same Store New England $ 77,240 $ 52,030 $ 156,085 $ 104,299 $ 2,751,535 Metro NY/NJ 106,452 73,858 219,266 153,511 4,097,021 Mid-Atlantic 84,634 59,217 172,954 122,975 3,462,890 Southeast Florida 7,364 4,298 14,868 8,423 393,329 Denver, CO 5,166 3,326 10,335 6,666 318,833 Pacific Northwest 28,105 19,932 57,263 41,065 1,049,913 Northern California 103,867 79,384 210,744 161,263 3,427,805 Southern California 109,869 76,433 227,468 160,671 4,345,382 Total Same Store 522,697 368,478 1,068,983 758,873 19,846,708 Other Stabilized 24,642 16,055 49,673 32,552 1,209,541 Development / Redevelopment 7,368 3,595 14,181 7,143 1,614,237 Land Held for Development N/A N/A N/A N/A 39,829 Non-allocated (2) 299 N/A 690 N/A 407,361 Total $ 555,006 $ 388,128 $ 1,133,527 $ 798,568 $ 23,117,676 __________________________________ (1) Does not include gross real estate assets held for sale or classified as held for sale subsequent to June 30, 2020 of $672,125. (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	6 Months Ended
	Jun. 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 six months ended June 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 (1,571) 180.32 Options Outstanding, June 30, 2021 302,924 $ 178.63 Options Exercisable, June 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 common shares (56,545) 156.00 Forfeited (240) 208.35 Outstanding at June 30, 2021 285,700 $ 206.06 __________________________________ (1) The amount of common shares 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 94,641 176.32 — Vested - restricted stock shares (66,038) 192.17 (71,535) Forfeited (709) 197.01 — Outstanding at June 30, 2021 159,618 $ 191.92 74,784 Total employee stock-based compensation cost recognized in income was $12,897,000 and $11,624,000 for the six months ended June 30, 2021 and 2020, respectively, and total capitalized stock-based compensation cost was $4,599,000 and $6,174,000 for the six months ended June 30, 2021 and 2020, respectively. At June 30, 2021, there was a total unrecognized compensation cost of $57,078,000 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 2.1 years. Forfeitures are included in compensation cost as they occur.

Related Party Arrangements

Related Party Arrangements	6 Months Ended
	Jun. 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 $808,000 and $926,000 for the three months ended June 30, 2021 and 2020, respectively, and $1,685,000 and $1,933,000 for the six months ended June 30, 2021 and 2020, respectively. In addition, the Company had outstanding receivables associated with its property and construction management roles of $3,199,000 and $5,408,000 as of June 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 $476,000 and $446,000 in the three months ended June 30, 2021 and 2020, respectively, and $941,000 and $901,000 in the six months ended June 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 $1,543,000 and $614,000 on June 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	6 Months Ended
	Jun. 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 June 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 June 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 % 1.5 % Earliest maturity date July 2021 September 2021 Latest maturity date February 2026 September 2021 ____________________________________ (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. During the six months ended June 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 six months ended June 30, 2021 included in interest expense, net on the accompanying Condensed Consolidated Statements of Comprehensive Income. In addition, during the three and six months ended June 30, 2021, the Company entered into $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 2021. The Company is party to five derivatives not designated as hedges at June 30, 2021 for which the fair value changes for the three and six months ended June 30, 2021 and 2020 were not material. The following table summarizes the deferred losses reclassified from accumulated other comprehensive loss as a component of interest expense, net (dollars in thousands): For the three months ended For the six months ended 6/30/2021 6/30/2020 6/30/2021 6/30/2020 Cash flow hedge losses reclassified to earnings $ 2,366 $ 2,301 $ 4,733 $ 4,250 The Company anticipates reclassifying approximately $9,467,000 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): 6/30/2021 Description Total Fair Value Quoted Prices Significant Significant Non Designated Hedges Interest Rate Caps $ 97 $ — $ 97 $ — Interest Rate Swaps - Assets 88 — 88 — Interest Rate Swaps - Liabilities (910) — (910) — DownREIT units (1,565) (1,565) — — Indebtedness Fixed rate unsecured notes (7,061,205) (7,061,205) — — Mortgage notes payable, variable rate unsecured notes and Term Loans (1,007,522) — (1,007,522) — Total $ (8,071,017) $ (7,062,770) $ (1,008,247) $ — 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	6 Months Ended
	Jun. 30, 2021
Subsequent Events [Abstract]
Subsequent Events	Subsequent EventsThe 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 did not identify any items for disclosure.

Organization, Basis of Presen_2

Organization, Basis of Presentation and Significant Accounting Policies (Policies)	6 Months Ended
	Jun. 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 (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, Southeast Florida, Denver, Colorado, the Pacific Northwest, and Northern and Southern California. The Company is pursuing opportunities in new expansion markets of Dallas and Austin, Texas, and Charlotte and Raleigh-Durham, North Carolina. At June 30, 2021, the Company owned or held a direct or indirect ownership interest in 272 operating apartment communities containing 80,958 apartment homes in 11 states and the District of Columbia. In addition, the Company owned or held a direct or indirect ownership interest in 16 communities under development that are expected to contain an aggregate of 4,791 apartment homes when completed, as well as The Park Loggia, which contains 172 for-sale residential condominiums, of which 96 have been sold as of June 30, 2021, and 66,000 square feet of commercial space, of which 87% has been leased as of June 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 23 communities that, if developed as expected, will contain an estimated 7,802 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 six months ended June 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 six months ended 6/30/2021 6/30/2020 6/30/2021 6/30/2020 Basic and diluted shares outstanding Weighted average common shares - basic 139,373,963 140,450,744 139,332,575 140,413,857 Weighted average DownREIT units outstanding 7,500 7,500 7,500 7,500 Effect of dilutive securities 269,176 279,916 261,451 330,974 Weighted average common shares - diluted 139,650,639 140,738,160 139,601,526 140,752,331 Calculation of Earnings per Share - basic Net income attributable to common stockholders $ 447,953 $ 170,828 $ 590,176 $ 338,799 Net income allocated to unvested restricted shares (902) (390) (1,267) (817) Net income attributable to common stockholders, adjusted $ 447,051 $ 170,438 $ 588,909 $ 337,982 Weighted average common shares - basic 139,373,963 140,450,744 139,332,575 140,413,857 Earnings per common share - basic $ 3.21 $ 1.21 $ 4.23 $ 2.41 Calculation of Earnings per Share - diluted Net income attributable to common stockholders $ 447,953 $ 170,828 $ 590,176 $ 338,799 Add: noncontrolling interests of DownREIT unitholders in consolidated partnerships 12 12 24 24 Adjusted net income attributable to common stockholders $ 447,965 $ 170,840 $ 590,200 $ 338,823 Weighted average common shares - diluted 139,650,639 140,738,160 139,601,526 140,752,331 Earnings per common share - diluted $ 3.21 $ 1.21 $ 4.23 $ 2.41 Certain options to purchase shares of common stock in the amount of 292,544 were outstanding as of June 30, 2021, but were not included in the computation of diluted earnings per share because such options were anti-dilutive for the period. All options to purchase shares of common stock outstanding as of June 30, 2020 are included in the computation of diluted earnings per share.
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.
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) that 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 six months ended June 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 June 30, 2021, or otherwise qualify as held for sale as of June 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 June 30, 2021 Management, development and other fees and other ancillary items $ — $ — $ — $ 808 $ 808 Rental and non-rental related income (2) 1,922 395 186 — 2,503 Total non-lease revenue (3) 1,922 395 186 808 3,311 Lease income (4) 498,719 29,104 22,890 — 550,713 Business interruption insurance proceeds — — — — — Total revenue $ 500,641 $ 29,499 $ 23,076 $ 808 $ 554,024 For the period ended June 30, 2020 Management, development and other fees and other ancillary items $ — $ — $ — $ 299 $ 299 Rental and non-rental related income (2) 1,848 482 78 — 2,408 Total non-lease revenue (3) 1,848 482 78 299 2,707 Lease income (4) 520,753 24,160 7,290 — 552,203 Business interruption insurance proceeds 96 — — — 96 Total revenue $ 522,697 $ 24,642 $ 7,368 $ 299 $ 555,006 For the six months ended Same Store Other Development/ Non- Total For the period ended June 30, 2021 Management, development and other fees and other ancillary items $ — $ — $ — $ 1,685 $ 1,685 Rental and non-rental related income (2) 3,571 821 327 — 4,719 Total non-lease revenue (3) 3,571 821 327 1,685 6,404 Lease income (4) 993,569 55,443 40,156 — 1,089,168 Business interruption insurance proceeds — — — — — Total revenue $ 997,140 $ 56,264 $ 40,483 $ 1,685 $ 1,095,572 For the period ended June 30, 2020 Management, development and other fees and other ancillary items $ — $ — $ — $ 690 $ 690 Rental and non-rental related income (2) 3,462 1,073 137 — 4,672 Total non-lease revenue (3) 3,462 1,073 137 690 5,362 Lease income (4) 1,065,425 48,600 14,044 — 1,128,069 Business interruption insurance proceeds 96 — — — 96 Total revenue $ 1,068,983 $ 49,673 $ 14,181 $ 690 $ 1,133,527 __________________________________ (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. (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 June 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, Lease Accounting, 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 (i) the duration and severity of the pandemic, (ii) the effectiveness of vaccines and the rate of vaccinations, (iii) the duration and nature of governmental responses to contain the spread of the disease and assist consumers and businesses, (iv) consumer and business responses to the pandemic, including preferences for where and how to live and work, and (v) how quickly and to what extent normal economic and operating conditions can resume. Because of this uncertainty, any estimate of the expected impact of the COVID-19 pandemic on results of operations, cash flows, financial condition, or liquidity for periods beyond the six months ended June 30, 2021 is uncertain. As of June 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 $15,065,000 and $20,099,000 for the three months ended June 30, 2021 and 2020, respectively, and $33,710,000 and $24,279,000 for six months ended June 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)	6 Months Ended
	Jun. 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 six months ended 6/30/2021 6/30/2020 6/30/2021 6/30/2020 Basic and diluted shares outstanding Weighted average common shares - basic 139,373,963 140,450,744 139,332,575 140,413,857 Weighted average DownREIT units outstanding 7,500 7,500 7,500 7,500 Effect of dilutive securities 269,176 279,916 261,451 330,974 Weighted average common shares - diluted 139,650,639 140,738,160 139,601,526 140,752,331 Calculation of Earnings per Share - basic Net income attributable to common stockholders $ 447,953 $ 170,828 $ 590,176 $ 338,799 Net income allocated to unvested restricted shares (902) (390) (1,267) (817) Net income attributable to common stockholders, adjusted $ 447,051 $ 170,438 $ 588,909 $ 337,982 Weighted average common shares - basic 139,373,963 140,450,744 139,332,575 140,413,857 Earnings per common share - basic $ 3.21 $ 1.21 $ 4.23 $ 2.41 Calculation of Earnings per Share - diluted Net income attributable to common stockholders $ 447,953 $ 170,828 $ 590,176 $ 338,799 Add: noncontrolling interests of DownREIT unitholders in consolidated partnerships 12 12 24 24 Adjusted net income attributable to common stockholders $ 447,965 $ 170,840 $ 590,200 $ 338,823 Weighted average common shares - diluted 139,650,639 140,738,160 139,601,526 140,752,331 Earnings per common share - diluted $ 3.21 $ 1.21 $ 4.23 $ 2.41
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 six months ended June 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 June 30, 2021, or otherwise qualify as held for sale as of June 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 June 30, 2021 Management, development and other fees and other ancillary items $ — $ — $ — $ 808 $ 808 Rental and non-rental related income (2) 1,922 395 186 — 2,503 Total non-lease revenue (3) 1,922 395 186 808 3,311 Lease income (4) 498,719 29,104 22,890 — 550,713 Business interruption insurance proceeds — — — — — Total revenue $ 500,641 $ 29,499 $ 23,076 $ 808 $ 554,024 For the period ended June 30, 2020 Management, development and other fees and other ancillary items $ — $ — $ — $ 299 $ 299 Rental and non-rental related income (2) 1,848 482 78 — 2,408 Total non-lease revenue (3) 1,848 482 78 299 2,707 Lease income (4) 520,753 24,160 7,290 — 552,203 Business interruption insurance proceeds 96 — — — 96 Total revenue $ 522,697 $ 24,642 $ 7,368 $ 299 $ 555,006 For the six months ended Same Store Other Development/ Non- Total For the period ended June 30, 2021 Management, development and other fees and other ancillary items $ — $ — $ — $ 1,685 $ 1,685 Rental and non-rental related income (2) 3,571 821 327 — 4,719 Total non-lease revenue (3) 3,571 821 327 1,685 6,404 Lease income (4) 993,569 55,443 40,156 — 1,089,168 Business interruption insurance proceeds — — — — — Total revenue $ 997,140 $ 56,264 $ 40,483 $ 1,685 $ 1,095,572 For the period ended June 30, 2020 Management, development and other fees and other ancillary items $ — $ — $ — $ 690 $ 690 Rental and non-rental related income (2) 3,462 1,073 137 — 4,672 Total non-lease revenue (3) 3,462 1,073 137 690 5,362 Lease income (4) 1,065,425 48,600 14,044 — 1,128,069 Business interruption insurance proceeds 96 — — — 96 Total revenue $ 1,068,983 $ 49,673 $ 14,181 $ 690 $ 1,133,527 __________________________________ (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. (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)	6 Months Ended
	Jun. 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 June 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"). 6/30/2021 12/31/2020 Fixed rate unsecured notes (1) $ 6,500,000 $ 6,500,000 Term Loans (1) 250,000 250,000 Fixed rate mortgage notes payable - conventional and tax-exempt (2) 380,030 408,964 Variable rate mortgage notes payable - conventional and tax-exempt (2) 465,050 470,850 Total mortgage notes payable and unsecured notes and Term Loans 7,595,080 7,629,814 Credit Facility — — Total mortgage notes payable, unsecured notes, Term Loans and Credit Facility $ 7,595,080 $ 7,629,814 _____________________________________ (1) Balances at June 30, 2021 and December 31, 2020 exclude $9,577 and $10,380, respectively, of debt discount, and $34,910 and $37,615, respectively, of deferred financing costs, as reflected in unsecured notes, net on the accompanying Condensed Consolidated Balance Sheets. (2) Balances at June 30, 2021 and December 31, 2020 exclude $14,083 and $14,478, respectively, of debt discount, and $2,877 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 June 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 $ 2,414 $ — $ — N/A 2022 9,918 — 450,000 2.950 % 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 176,078 245,338 600,000 2.450 % 350,000 3.900 % 300,000 4.150 % 300,000 4.350 % $ 297,392 $ 547,688 $ 6,750,000

Equity (Tables)

Equity (Tables)	6 Months Ended
	Jun. 30, 2021
Stockholders' Equity Note [Abstract]
Summary of changes in equity	The following summarizes the changes in equity for the six months ended June 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 The following summarizes the changes in equity for the six months ended June 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

Investments in Real Estate En_2

Investments in Real Estate Entities (Tables)	6 Months Ended
	Jun. 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 discussed above as of the dates presented, including development joint ventures started and unconsolidated communities sold during the respective periods (dollars in thousands): 6/30/2021 12/31/2020 (unaudited) Assets: Real estate, net $ 1,147,860 $ 1,249,730 Other assets 473,193 255,606 Total assets $ 1,621,053 $ 1,505,336 Liabilities and partners' capital: Mortgage notes payable, net (1) $ 637,676 $ 751,257 Other liabilities 169,258 163,808 Partners' capital 814,119 590,271 Total liabilities and partners' capital $ 1,621,053 $ 1,505,336 _________________________________ (1) The Company has not guaranteed the 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 six months ended 6/30/2021 6/30/2020 6/30/2021 6/30/2020 (unaudited) (unaudited) Rental and other income (1) $ 41,809 $ 30,427 $ 66,744 $ 63,499 Operating and other expenses (12,126) (11,732) (24,293) (23,912) Gain on sale of communities 164,317 40 164,317 40 Interest expense, net (7,582) (8,053) (15,250) (16,109) Depreciation expense (7,441) (8,713) (15,919) (17,402) Net income $ 178,977 $ 1,969 $ 175,599 $ 6,116 Company's share of net income from investments in unconsolidated entities $ 27,087 $ 1,041 $ 27,149 $ 2,746 Amortization of excess investment and other (528) (529) (1,057) (1,059) Income from investments in unconsolidated entities $ 26,559 $ 512 $ 26,092 $ 1,687

Segment Reporting (Tables)

Segment Reporting (Tables)	6 Months Ended
	Jun. 30, 2021
Segment Reporting [Abstract]
Schedule of reconciliation of NOI to net income	A reconciliation of NOI to net income for the three and six months ended June 30, 2021 and 2020 is as follows (dollars in thousands): For the three months ended For the six months ended 6/30/2021 6/30/2020 6/30/2021 6/30/2020 Net income $ 447,977 $ 170,869 $ 590,211 $ 338,875 Indirect operating expenses, net of corporate income 24,318 23,407 48,788 46,206 Expensed transaction, development and other pursuit costs, net of recoveries 1,653 388 1,483 3,722 Interest expense, net 56,104 53,399 108,717 109,313 Loss (gain) on extinguishment of debt, net — 268 (122) 9,438 General and administrative expense 18,465 15,573 35,817 32,893 Income from investments in unconsolidated entities (26,559) (512) (26,092) (1,687) Depreciation expense 184,472 176,249 367,769 354,160 Income tax expense (benefit) 10 (1,133) (745) (1,042) Casualty and impairment loss 1,177 — 1,177 — Gain on sale of communities (334,569) (35,295) (388,296) (59,731) Gain on other real estate transactions, net (32) (156) (459) (199) Net for-sale condominium activity 647 (1,348) 1,560 (4,808) Net operating income from real estate assets sold or held for sale (4,749) (13,581) (10,549) (28,572) Net operating income $ 368,914 $ 388,128 $ 729,259 $ 798,568
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 six months ended 6/30/2021 6/30/2020 6/30/2021 6/30/2020 Rental income from real estate assets sold or held for sale $ 7,719 $ 21,399 $ 17,307 $ 44,529 Operating expenses from real estate assets sold or held for sale (2,970) (7,818) (6,758) (15,957) Net operating income from real estate assets sold or held for sale $ 4,749 $ 13,581 $ 10,549 $ 28,572
Schedule of details of segment information	For the three months ended For the six months ended Total NOI Total NOI Gross real estate (1) For the period ended June 30, 2021 Same Store New England $ 74,259 $ 47,895 $ 147,577 $ 94,163 $ 2,772,638 Metro NY/NJ 105,355 70,944 210,304 142,584 4,114,155 Mid-Atlantic 82,232 54,823 163,460 110,083 3,485,698 Southeast Florida 7,706 4,557 14,948 8,746 395,009 Denver, CO 5,853 3,935 11,505 7,954 319,994 Pacific Northwest 26,935 18,298 53,548 36,192 1,054,701 Northern California 89,591 63,506 179,997 127,569 3,450,054 Southern California 108,710 73,364 215,801 145,899 4,373,247 Total Same Store 500,641 337,322 997,140 673,190 19,965,496 Other Stabilized 29,499 19,123 56,264 36,049 1,338,844 Development / Redevelopment 23,076 12,469 40,483 20,020 2,324,779 Land Held for Development N/A N/A N/A N/A 100,106 Non-allocated (2) 808 N/A 1,685 N/A 322,576 Total $ 554,024 $ 368,914 $ 1,095,572 $ 729,259 $ 24,051,801 For the period ended June 30, 2020 Same Store New England $ 77,240 $ 52,030 $ 156,085 $ 104,299 $ 2,751,535 Metro NY/NJ 106,452 73,858 219,266 153,511 4,097,021 Mid-Atlantic 84,634 59,217 172,954 122,975 3,462,890 Southeast Florida 7,364 4,298 14,868 8,423 393,329 Denver, CO 5,166 3,326 10,335 6,666 318,833 Pacific Northwest 28,105 19,932 57,263 41,065 1,049,913 Northern California 103,867 79,384 210,744 161,263 3,427,805 Southern California 109,869 76,433 227,468 160,671 4,345,382 Total Same Store 522,697 368,478 1,068,983 758,873 19,846,708 Other Stabilized 24,642 16,055 49,673 32,552 1,209,541 Development / Redevelopment 7,368 3,595 14,181 7,143 1,614,237 Land Held for Development N/A N/A N/A N/A 39,829 Non-allocated (2) 299 N/A 690 N/A 407,361 Total $ 555,006 $ 388,128 $ 1,133,527 $ 798,568 $ 23,117,676 __________________________________ (1) Does not include gross real estate assets held for sale or classified as held for sale subsequent to June 30, 2020 of $672,125. (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)	6 Months Ended
	Jun. 30, 2021
Share-based Payment Arrangement [Abstract]
Share-based Payment Arrangement, Option, Activity	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 (1,571) 180.32 Options Outstanding, June 30, 2021 302,924 $ 178.63 Options Exercisable, June 30, 2021 10,380 $ 130.90
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 common shares (56,545) 156.00 Forfeited (240) 208.35 Outstanding at June 30, 2021 285,700 $ 206.06 __________________________________ (1) The amount of common shares 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.
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 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 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 94,641 176.32 — Vested - restricted stock shares (66,038) 192.17 (71,535) Forfeited (709) 197.01 — Outstanding at June 30, 2021 159,618 $ 191.92 74,784

Fair Value (Tables)

Fair Value (Tables)	6 Months Ended
	Jun. 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 June 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 % 1.5 % Earliest maturity date July 2021 September 2021 Latest maturity date February 2026 September 2021 ____________________________________ (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 as a component of interest expense, net (dollars in thousands): For the three months ended For the six months ended 6/30/2021 6/30/2020 6/30/2021 6/30/2020 Cash flow hedge losses reclassified to earnings $ 2,366 $ 2,301 $ 4,733 $ 4,250
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): 6/30/2021 Description Total Fair Value Quoted Prices Significant Significant Non Designated Hedges Interest Rate Caps $ 97 $ — $ 97 $ — Interest Rate Swaps - Assets 88 — 88 — Interest Rate Swaps - Liabilities (910) — (910) — DownREIT units (1,565) (1,565) — — Indebtedness Fixed rate unsecured notes (7,061,205) (7,061,205) — — Mortgage notes payable, variable rate unsecured notes and Term Loans (1,007,522) — (1,007,522) — Total $ (8,071,017) $ (7,062,770) $ (1,008,247) $ — 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		6 Months Ended		18 Months Ended
	Jun. 30, 2021USD ($)homecommunityresidential_condominiumft²state	Jun. 30, 2020USD ($)	Jun. 30, 2021USD ($)homecommunityresidential_condominiumft²state	Jun. 30, 2020USD ($)	Jun. 30, 2021homecommunityresidential_condominiumft²state
Real Estate Properties [Line Items]
Number of operating apartment communities | community	272		272		272
Number of apartment homes included in operating apartment communities owned | home	80,958		80,958		80,958
Number of states where operating apartment communities owned are located | state	11		11		11
Number of owned communities under construction | community	16		16		16
Expected number of apartment homes under construction | home	4,791		4,791		4,791
Number of Residential Condominium Units Sold | residential_condominium	16		26		96
Communities under development rights | community	23		23		23
Estimated number of apartment homes in communities to be developed | home	7,802		7,802		7,802
Total revenue | $	$ 561,743	$ 576,405	$ 1,112,879	$ 1,178,056
Accounts Receivable, Credit Loss Expense (Reversal) | $	$ 15,065	$ 20,099	$ 33,710	$ 24,279
The Park Loggia [Member]
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				6 Months Ended
	Jun. 30, 2021	Mar. 31, 2021	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2021	Jun. 30, 2020
Basic and diluted shares outstanding
Weighted average common shares - basic (in shares)	139,373,963		140,450,744		139,332,575	140,413,857
Weighted average DownREIT units outstanding (in shares)	7,500		7,500		7,500	7,500
Effect of dilutive securities (in shares)	269,176		279,916		261,451	330,974
Weighted average common shares - diluted (in shares)	139,650,639		140,738,160		139,601,526	140,752,331
Calculation of Earnings per Share - basic
Net income attributable to common stockholders	$ 447,953	$ 142,223	$ 170,828	$ 167,971	$ 590,176	$ 338,799
Net income allocated to unvested restricted shares	(902)		(390)		(1,267)	(817)
Net income attributable to common stockholders, adjusted	$ 447,051		$ 170,438		$ 588,909	$ 337,982
Weighted average common shares - basic (in shares)	139,373,963		140,450,744		139,332,575	140,413,857
Earnings per common share - basic (in dollars per share)	$ 3.21		$ 1.21		$ 4.23	$ 2.41
Calculation of Earnings per Share - diluted
Net income attributable to common stockholders	$ 447,953	$ 142,223	$ 170,828	$ 167,971	$ 590,176	$ 338,799
Add: noncontrolling interests of DownREIT unitholders in consolidated partnerships	12		12		24	24
Adjusted net income attributable to common stockholders	$ 447,965		$ 170,840		$ 590,200	$ 338,823
Weighted average common shares - diluted (in shares)	139,650,639		140,738,160		139,601,526	140,752,331
Earnings per common share - diluted (in dollars per share)	$ 3.21		$ 1.21		$ 4.23	$ 2.41
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount					292,544

Organization, Basis of Presen_6

Organization, Basis of Presentation and Significant Accounting Policies (Details 3) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Disaggregation of Revenue [Line Items]
Management, development and other fees	$ 808	$ 926	$ 1,685	$ 1,933
Rental and other income	560,935	575,479	1,111,194	1,176,123
Total revenue	561,743	576,405	1,112,879	1,178,056
Operating Segments | Same Store
Disaggregation of Revenue [Line Items]
Total revenue	500,641	522,697	997,140	1,068,983
Operating Segments | Other Stabilized
Disaggregation of Revenue [Line Items]
Total revenue	29,499	24,642	56,264	49,673
Non-allocated
Disaggregation of Revenue [Line Items]
Total revenue	808	299	1,685	690
Continuing Operations
Disaggregation of Revenue [Line Items]
Management, development and other fees	3,311	2,707	6,404	5,362
Rental and other income	550,713	552,203	1,089,168	1,128,069
Gain on Business Interruption Insurance Recovery	0	96	0	96
Total revenue	554,024	555,006	1,095,572	1,133,527
Continuing Operations | Management, development and other fees and other ancillary items
Disaggregation of Revenue [Line Items]
Management, development and other fees	808	299	1,685	690
Continuing Operations | Rental and non-rental related income
Disaggregation of Revenue [Line Items]
Management, development and other fees	2,503	2,408	4,719	4,672
Continuing Operations | Operating Segments | Same Store
Disaggregation of Revenue [Line Items]
Management, development and other fees	1,922	1,848	3,571	3,462
Rental and other income	498,719	520,753	993,569	1,065,425
Gain on Business Interruption Insurance Recovery	0	96	0	96
Total revenue	500,641	522,697	997,140	1,068,983
Continuing Operations | Operating Segments | Other Stabilized
Disaggregation of Revenue [Line Items]
Management, development and other fees	395	482	821	1,073
Rental and other income	29,104	24,160	55,443	48,600
Gain on Business Interruption Insurance Recovery	0	0	0	0
Total revenue	29,499	24,642	56,264	49,673
Continuing Operations | Operating Segments | Development/ Redevelopment
Disaggregation of Revenue [Line Items]
Management, development and other fees	186	78	327	137
Rental and other income	22,890	7,290	40,156	14,044
Gain on Business Interruption Insurance Recovery	0	0	0	0
Total revenue	23,076	7,368	40,483	14,181
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	1,922	1,848	3,571	3,462
Continuing Operations | Operating Segments | Rental and non-rental related income | Other Stabilized
Disaggregation of Revenue [Line Items]
Management, development and other fees	395	482	821	1,073
Continuing Operations | Operating Segments | Rental and non-rental related income | Development/ Redevelopment
Disaggregation of Revenue [Line Items]
Management, development and other fees	186	78	327	137
Continuing Operations | Non-allocated
Disaggregation of Revenue [Line Items]
Management, development and other fees	808	299	1,685	690
Rental and other income	0	0	0	0
Gain on Business Interruption Insurance Recovery	0	0	0	0
Total revenue	808	299	1,685	690
Continuing Operations | Non-allocated | Management, development and other fees and other ancillary items
Disaggregation of Revenue [Line Items]
Management, development and other fees	808	299	1,685	690
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		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Interest Capitalized
Capitalized interest during the development and redevelopment of real estate assets	$ 8,362	$ 11,019	$ 17,161	$ 22,517

Mortgage Notes Payable, Unsec_3

Mortgage Notes Payable, Unsecured Notes and Credit Facility (Details) - USD ($)	Jun. 30, 2021	Dec. 31, 2020
Notes Payable, Unsecured Notes and Credit Facility
Total mortgage notes payable and unsecured notes and Term Loans	$ 7,595,080,000	$ 7,629,814,000
Credit Facility	0	0
Total mortgage notes payable, unsecured notes, Term Loans and Credit Facility	7,595,080,000	7,629,814,000
Unsecured notes
Notes Payable, Unsecured Notes and Credit Facility
Long-term Debt, Percentage Bearing Fixed Interest, Amount	6,500,000,000	6,500,000,000
Total mortgage notes payable and unsecured notes and Term Loans	6,750,000,000
Amount of debt discount	9,577,000	10,380,000
Amount of deferred financing costs, net	34,910,000	37,615,000
Term Loans
Notes Payable, Unsecured Notes and Credit Facility
Variable rate notes	250,000,000	250,000,000
Secured notes
Notes Payable, Unsecured Notes and Credit Facility
Long-term Debt, Percentage Bearing Fixed Interest, Amount	380,030,000	408,964,000
Variable rate notes	465,050,000	470,850,000
Total mortgage notes payable and unsecured notes and Term Loans	547,688,000
Amount of debt discount	14,083,000	14,478,000
Amount of deferred financing costs, net	2,877,000	3,004,000
Line of Credit [Member]
Notes Payable, Unsecured Notes and Credit Facility
Credit Facility	$ 0	$ 0

Mortgage Notes Payable, Unsec_4

Mortgage Notes Payable, Unsecured Notes and Credit Facility (Details 2) - USD ($)	1 Months Ended	6 Months Ended
	Jan. 31, 2021	Jun. 30, 2021	Dec. 31, 2020
Notes Payable, Unsecured Notes and Credit Facility
Credit Facility		$ 0	$ 0
Net carrying value of apartment communities and improved land parcels securing debt		1,373,062,000
Secured Debt [Member]
Notes Payable, Unsecured Notes and Credit Facility
Long-term Debt, Percentage Bearing Fixed Interest, Amount		380,030,000	408,964,000
Unsecured notes
Notes Payable, Unsecured Notes and Credit Facility
Long-term Debt, Percentage Bearing Fixed Interest, Amount		6,500,000,000	6,500,000,000
Notes Payable Maturities 2021 [Member]
Notes Payable, Unsecured Notes and Credit Facility
Debt Instrument, Interest Rate, Stated Percentage	5.37%
Line of Credit [Member]
Notes Payable, Unsecured Notes and Credit Facility
Available borrowing capacity		$ 1,750,000,000
Annual facility fee, percentage		0.125%
Annual facility fee		$ 2,188,000
Credit Facility		0	0
Outstanding balance of letters of credit		$ 2,599,000	2,900,000
Line of Credit [Member] | 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)		0.88%
Other Letter of Credit [Member]
Notes Payable, Unsecured Notes and Credit Facility
Outstanding balance of letters of credit		$ 36,682,000	$ 32,079,000
Fixed Rate Mortgage Notes Payable [Member]
Notes Payable, Unsecured Notes and Credit Facility
Weighted average interest rate, debt (as a percent)		3.80%	3.80%
Variable Rate Mortgage Notes Payable Unsecured Term Loan and Credit Facility [Member]
Notes Payable, Unsecured Notes and Credit Facility
Weighted average interest rate, debt (as a percent)		1.60%	1.70%
Avalon San Bruno II | Notes Payable Maturities 2021 [Member] | Secured Debt [Member]
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	6 Months Ended
	Jun. 30, 2021	Jan. 31, 2021	Dec. 31, 2020
Notes Payable, Unsecured Notes and Credit Facility
Mortgage notes payable and unsecured notes	$ 7,595,080		$ 7,629,814
Notes Payable Maturities 2021 [Member]
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	297,392
Mortgage notes payable and unsecured notes	547,688
Secured notes | Notes Payable Maturities 2021 [Member]
Notes Payable, Unsecured Notes and Credit Facility
Secured notes payments	2,414
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 [Member]
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 [Member]
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	245,338
Unsecured notes
Notes Payable, Unsecured Notes and Credit Facility
Mortgage notes payable and unsecured notes	6,750,000
Unsecured notes | Notes payable maturing in 2022
Notes Payable, Unsecured Notes and Credit Facility
Mortgage notes payable and unsecured notes	$ 450,000
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 [Member]
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 [Member]
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 [Member]
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 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 ($)	3 Months Ended				6 Months Ended
	Jun. 30, 2021	Mar. 31, 2021	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2021	Jun. 30, 2020	Jul. 31, 2020
Class of Stock [Line Items]
Issuance of common stock, net					$ 2,372,000	$ 1,613,000
Changes in equity
Beginning Balance	$ 10,668,904,000	$ 10,752,174,000	$ 10,912,542,000	$ 10,990,198,000	10,752,174,000	10,990,198,000
Net income attributable to common stockholders	447,953,000	142,223,000	170,828,000	167,971,000	590,176,000	338,799,000
Loss on cash flow hedges	(822,000)		(1,461,000)	(17,603,000)	(822,000)	(19,064,000)
Cash flow hedge losses reclassified to earnings	2,366,000	2,367,000	2,301,000	1,949,000	4,733,000	4,250,000
Change in redemption value of redeemable noncontrolling interest	(255,000)	(273,000)	(146,000)	471,000
Noncontrolling interest distribution and income allocation	(7,000)	(16,000)	1,000	(35,000)
Dividends, Common Stock	(222,451,000)	(221,779,000)	(224,172,000)	(224,083,000)
Issuance of common stock, net of withholdings	2,496,000	(13,078,000)	1,188,000	(14,107,000)
Amortization of deferred compensation	10,403,000	7,286,000	9,724,000	7,781,000
Ending Balance	$ 10,908,587,000	$ 10,668,904,000	$ 10,870,805,000	$ 10,912,542,000	10,908,587,000	10,870,805,000
Dividends declared to common stockholders (in dollars per share)	$ 1.59	$ 1.59	$ 1.59	$ 1.59
Amended 2005 Stock Repurchase Program [Member]
Changes in equity
Stock Repurchase Program, Authorized Amount							$ 500,000,000
Common stock
Changes in equity
Beginning Balance	$ 1,396,000	$ 1,395,000	$ 1,407,000	$ 1,406,000	1,395,000	1,406,000
Issuance of common stock, net of withholdings		1,000		1,000
Ending Balance	1,396,000	1,396,000	1,407,000	1,407,000	1,396,000	1,407,000
Additional paid-in capital
Changes in equity
Beginning Balance	10,657,665,000	10,664,416,000	10,732,022,000	10,736,733,000	10,664,416,000	10,736,733,000
Issuance of common stock, net of withholdings	2,496,000	(14,037,000)	1,050,000	(12,492,000)
Amortization of deferred compensation	10,403,000	7,286,000	9,724,000	7,781,000
Ending Balance	10,670,564,000	10,657,665,000	10,742,796,000	10,732,022,000	10,670,564,000	10,742,796,000
Accumulated earnings less dividends
Changes in equity
Beginning Balance	47,151,000	126,022,000	225,656,000	282,913,000	126,022,000	282,913,000
Net income attributable to common stockholders	447,953,000	142,223,000	170,828,000	167,971,000
Change in redemption value of redeemable noncontrolling interest	(255,000)	(273,000)	(146,000)	471,000	(528,000)	325,000
Dividends, Common Stock	(222,451,000)	(221,779,000)	(224,172,000)	(224,083,000)
Issuance of common stock, net of withholdings		958,000	138,000	(1,616,000)
Ending Balance	272,398,000	47,151,000	172,304,000	225,656,000	272,398,000	172,304,000
Accumulated other comprehensive loss
Changes in equity
Beginning Balance	(37,883,000)	(40,250,000)	(47,157,000)	(31,503,000)	(40,250,000)	(31,503,000)
Loss on cash flow hedges	(822,000)		(1,461,000)	(17,603,000)
Cash flow hedge losses reclassified to earnings	2,366,000	2,367,000	2,301,000	1,949,000
Ending Balance	(36,339,000)	(37,883,000)	(46,317,000)	(47,157,000)	(36,339,000)	(46,317,000)
Parent [Member]
Changes in equity
Beginning Balance	10,668,329,000	10,751,583,000	10,911,928,000	10,989,549,000	10,751,583,000	10,989,549,000
Net income attributable to common stockholders	447,953,000	142,223,000	170,828,000	167,971,000
Loss on cash flow hedges	(822,000)		(1,461,000)	(17,603,000)
Cash flow hedge losses reclassified to earnings	2,366,000	2,367,000	2,301,000	1,949,000
Change in redemption value of redeemable noncontrolling interest	(255,000)	(273,000)	(146,000)	471,000
Dividends, Common Stock	(222,451,000)	(221,779,000)	(224,172,000)	(224,083,000)
Issuance of common stock, net of withholdings	2,496,000	(13,078,000)	1,188,000	(14,107,000)
Amortization of deferred compensation	10,403,000	7,286,000	9,724,000	7,781,000
Ending Balance	10,908,019,000	10,668,329,000	10,870,190,000	10,911,928,000	10,908,019,000	10,870,190,000
Noncontrolling Interest [Member]
Changes in equity
Beginning Balance	575,000	591,000	614,000	649,000	591,000	649,000
Noncontrolling interest distribution and income allocation	(7,000)	(16,000)	1,000	(35,000)
Ending Balance	$ 568,000	$ 575,000	$ 615,000	$ 614,000	568,000	$ 615,000
Continuous Equity Program CEP V [Member]
Class of Stock [Line Items]
Issuance of common stock, net					$ 0

Equity (Details 2)

Equity (Details 2) - USD ($)	6 Months Ended
	Jun. 30, 2021	Jun. 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
Preferred stock, shares authorized (in shares)	50,000,000		50,000,000
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period	2,126
Common stock issued through the dividend reinvestment plan (in shares)	1,561	1,183
Number of shares of stock grants withheld (in shares)	74,726	73,089
Stock Issued During Period, Shares, Employee Stock Purchase Plans	12,145
Stock issued during period, shares, share-based compensation, forfeited (in shares)	709
Treasury Stock, Shares, Acquired	0
Stock Repurchase Program, Remaining Authorized Repurchase Amount	$ 316,148,000
Issuance of common stock, net	2,372,000	$ 1,613,000
2020 Stock Repurchase Program [Member]
Class of Stock [Line Items]
Stock Repurchase Program, Authorized Amount				$ 500,000,000
Amended 2005 Stock Repurchase Program [Member]
Class of Stock [Line Items]
Stock Repurchase Program, Authorized Amount				$ 500,000,000
Continuous Equity Program CEP V [Member]
Class of Stock [Line Items]
Maximum value of shares of common stock that can be sold (in dollars)	1,000,000,000
Common stock value, remaining to be authorized under continuous equity program	752,878,000
Issuance of common stock, net	$ 0
Maximum | Continuous Equity Program CEP V [Member]
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)	151,186	164,526

Investments in Real Estate En_3

Investments in Real Estate Entities - Narrative of Investment in Real Estate Entities (Details) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021USD ($)homeentity	Jun. 30, 2020USD ($)	Jun. 30, 2021USD ($)communityentityhome	Jun. 30, 2020USD ($)
Equity method investment
Casualty and impairment loss	$ 1,177	$ 0	$ 1,177	$ 0
Payments to Acquire Other Real Estate			$ 118,572	0
AC JV
Equity method investment
Number of Apartment Communities Sold | community			2
Land Parcel [Member]
Equity method investment
Casualty and impairment loss	0	0	$ 0	0
The Park Loggia [Member]
Equity method investment
Casualty and impairment loss	0	$ 0	0	$ 0
Proceeds from Sale of Real Estate	$ 38,392		53,001
Avalon Arundel Crossing East
Equity method investment
Number of Apartment Homes Acquired | home	384
Payments to Acquire Other Real Estate	$ 119,000
Avalon North Point and Avalon North Point Lofts | Notes Payable Maturities 2021 [Member] | Secured Debt [Member]
Equity method investment
Repayments of Secured Debt			$ 111,653
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		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
ASSETS
Real estate, net	$ 18,144,531		$ 18,144,531		$ 18,233,781
Total assets	19,316,625		19,316,625		19,199,144
LIABILITIES AND EQUITY
Mortgage notes payable, net	828,120		828,120		862,332
Partners' capital	10,908,019		10,908,019		10,751,583
Total liabilities and equity	19,316,625		19,316,625		19,199,144
Combined summary of the operating results of the accounted for using the equity method
Rental and other income	561,743	$ 576,405	1,112,879	$ 1,178,056
Costs and Expenses	(474,269)	(443,980)	(936,700)	(906,648)
Gains (Losses) on Sales of Investment Real Estate	334,569	35,295	388,296	59,731
Interest expense, net	(56,104)	(53,399)	(108,717)	(109,313)
Depreciation expense	(184,472)	(176,249)	(367,769)	(354,160)
Net income	447,977	170,869	590,211	338,875
Equity Method Investment, Net Income (Loss), Portion Attributable To Parent	27,087	1,041	27,149	2,746
Equity Method Investments, Amortization Of Excess Investment And Other	(528)	(529)	(1,057)	(1,059)
Income from investments in unconsolidated entities	26,559	512	26,092	1,687
Equity Method Investment, Nonconsolidated Investee or Group of Investees
ASSETS
Real estate, net	1,147,860		1,147,860		1,249,730
Other assets	473,193		473,193		255,606
Total assets	1,621,053		1,621,053		1,505,336
LIABILITIES AND EQUITY
Mortgage notes payable, net	637,676		637,676		751,257
Other liabilities	169,258		169,258		163,808
Partners' capital	814,119		814,119		590,271
Total liabilities and equity	1,621,053		1,621,053		$ 1,505,336
Combined summary of the operating results of the accounted for using the equity method
Rental and other income	41,809	30,427	66,744	63,499
Costs and Expenses	(12,126)	(11,732)	(24,293)	(23,912)
Gains (Losses) on Sales of Investment Real Estate	164,317	40	164,317	40
Interest expense, net	(7,582)	(8,053)	(15,250)	(16,109)
Depreciation expense	(7,441)	(8,713)	(15,919)	(17,402)
Net income	$ 178,977	$ 1,969	$ 175,599	$ 6,116

Investments in Real Estate En_5

Investments in Real Estate Entities - Expensed Acquisition, Development and Other Pursuit Costs and Impairment of Long-Lived Assets & Casualty Gains and Losses (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Equity Method Investments and Joint Ventures [Abstract]
Other than Temporary Impairment Losses, Investments	$ 0	$ 0	$ 0	$ 0
Casualty and impairment loss	$ 1,177	$ 0	$ 1,177	$ 0

Real Estate Disposition Activ_2

Real Estate Disposition Activities (Details) ft² in Thousands	3 Months Ended			6 Months Ended		18 Months Ended
	Jun. 30, 2021USD ($)homeresidential_condominiumft²community	Mar. 31, 2021USD ($)home	Jun. 30, 2020USD ($)	Jun. 30, 2021USD ($)residential_condominiumft²community	Jun. 30, 2020USD ($)	Jun. 30, 2021USD ($)residential_condominiumft²community	Dec. 31, 2020USD ($)
Summary of income from discontinued operations
Gains (Losses) on Sales of Investment Real Estate	$ 334,569,000		$ 35,295,000	$ 388,296,000	$ 59,731,000
Number Of Communities Held For Sale | community	0			0		0
Number of Residential Condominium Units Sold | residential_condominium	16			26		96
Gain (Loss) on Sale of Other Investments				$ 706,000	7,446,000
Number of Residential Condominiums Remaining to be Sold | residential_condominium	76			76		76
Other Selling, General and Administrative Expense	$ 1,222,000		$ 1,196,000	$ 2,266,000	$ 2,639,000
For-sale condominium inventory	$ 220,022,000			220,022,000		$ 220,022,000	$ 267,219,000
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
The Park Loggia [Member]
Summary of income from discontinued operations
Proceeds from Sale of Real Estate	$ 38,392,000			$ 53,001,000
Number Of Residential Condominium Units | residential_condominium	172			172		172
Commercial Square Feet | ft²	66			66		66
Gain (Loss) on Sale of Other Investments	$ 575,000			$ 706,000

Commitments and Contingencies -

Commitments and Contingencies - Narrative (Details) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021USD ($)communityLeaseproperty	Jun. 30, 2020USD ($)	Jun. 30, 2021USD ($)communityLeaseproperty	Jun. 30, 2020USD ($)	Dec. 31, 2020USD ($)
Lessee, Lease, Description [Line Items]
Number Of Office Leases | Lease	13		13
Operating lease assets	$ 129,064		$ 129,064		$ 133,581
Operating lease obligation	157,305		157,305		161,313
Operating Lease, Expense	3,896	$ 4,240	7,723	$ 8,157
Finance lease asset	25,371		25,371		21,685
Finance lease obligation	$ 20,143		$ 20,143		$ 20,166
Properties on Land Subject to Land Leases
Lessee, Lease, Description [Line Items]
Number Of operating apartment communities owned | community	9		9
Number of commercial properties owned | property	2		2
Assets Held under Operating Leases [Member]
Lessee, Lease, Description [Line Items]
Number Of operating apartment communities owned | community	8		8
Assets Held under Finance Leases [Member]
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		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Segment Reporting Information [Line Items]
Total revenue	$ 561,743	$ 576,405	$ 1,112,879	$ 1,178,056
Reconciliation of NOI to net income
Net income	447,977	170,869	590,211	338,875
Indirect operating expenses, net of corporate income	24,318	23,407	48,788	46,206
Other Nonoperating Income (Expense)	1,653	388	1,483	3,722
Interest Expense	56,104	53,399	108,717	109,313
(Gain) loss on extinguishment of debt, net	0	(268)	122	(9,438)
General and administrative expense	18,465	15,573	35,817	32,893
Income from investments in unconsolidated entities	(26,559)	(512)	(26,092)	(1,687)
Depreciation expense	184,472	176,249	367,769	354,160
Income tax expense (benefit)	10	(1,133)	(745)	(1,042)
Casualty and impairment loss	1,177	0	1,177	0
Gain on sale of communities	(334,569)	(35,295)	(388,296)	(59,731)
Gain on other real estate transactions, net	(32)	(156)	(459)	(199)
Net for-sale condominium activity	647	(1,348)	1,560	(4,808)
Net operating income from real estate assets sold or held for sale	(4,749)	(13,581)	(10,549)	(28,572)
Net operating income	$ 368,914	$ 388,128	$ 729,259	$ 798,568
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	1.50%	0.50%	1.50%	1.10%

Segment Reporting (Details 2)

Segment Reporting (Details 2) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Segment Reporting [Abstract]
Rental income from real estate assets sold or held for sale	$ 7,719	$ 21,399	$ 17,307	$ 44,529
Operating expenses from real estate assets sold or held for sale	(2,970)	(7,818)	(6,758)	(15,957)
Net operating income from real estate assets sold or held for sale	$ 4,749	$ 13,581	$ 10,549	$ 28,572

Segment Reporting (Details 3)

Segment Reporting (Details 3) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Segment Reporting
Total revenue	$ 561,743	$ 576,405	$ 1,112,879	$ 1,178,056
NOI	368,914	388,128	729,259	798,568
Gross real estate	24,051,801	23,117,676	24,051,801	23,117,676
Operating Segments | Established
Segment Reporting
Total revenue	500,641	522,697	997,140	1,068,983
NOI	337,322	368,478	673,190	758,873
Gross real estate	19,965,496	19,846,708	19,965,496	19,846,708
Operating Segments | Established | New England
Segment Reporting
Total revenue	74,259	77,240	147,577	156,085
NOI	47,895	52,030	94,163	104,299
Gross real estate	2,772,638	2,751,535	2,772,638	2,751,535
Operating Segments | Established | Metro NY/NJ
Segment Reporting
Total revenue	105,355	106,452	210,304	219,266
NOI	70,944	73,858	142,584	153,511
Gross real estate	4,114,155	4,097,021	4,114,155	4,097,021
Operating Segments | Established | Mid-Atlantic
Segment Reporting
Total revenue	82,232	84,634	163,460	172,954
NOI	54,823	59,217	110,083	122,975
Gross real estate	3,485,698	3,462,890	3,485,698	3,462,890
Operating Segments | Established | Southeast Florida
Segment Reporting
Total revenue	7,706	7,364	14,948	14,868
NOI	4,557	4,298	8,746	8,423
Gross real estate	395,009	393,329	395,009	393,329
Operating Segments | Established | Denver, Colorado
Segment Reporting
Total revenue	5,853	5,166	11,505	10,335
NOI	3,935	3,326	7,954	6,666
Gross real estate	319,994	318,833	319,994	318,833
Operating Segments | Established | Pacific Northwest
Segment Reporting
Total revenue	26,935	28,105	53,548	57,263
NOI	18,298	19,932	36,192	41,065
Gross real estate	1,054,701	1,049,913	1,054,701	1,049,913
Operating Segments | Established | Northern California
Segment Reporting
Total revenue	89,591	103,867	179,997	210,744
NOI	63,506	79,384	127,569	161,263
Gross real estate	3,450,054	3,427,805	3,450,054	3,427,805
Operating Segments | Established | Southern California
Segment Reporting
Total revenue	108,710	109,869	215,801	227,468
NOI	73,364	76,433	145,899	160,671
Gross real estate	4,373,247	4,345,382	4,373,247	4,345,382
Operating Segments | Other Stabilized
Segment Reporting
Total revenue	29,499	24,642	56,264	49,673
NOI	19,123	16,055	36,049	32,552
Gross real estate	1,338,844	1,209,541	1,338,844	1,209,541
Operating Segments | Development / Redevelopment
Segment Reporting
Total revenue	23,076	7,368	40,483	14,181
NOI	12,469	3,595	20,020	7,143
Gross real estate	2,324,779	1,614,237	2,324,779	1,614,237
Operating Segments | Disposals [Member]
Segment Reporting
Gross real estate		672,125		672,125
Land Held for Future Development
Segment Reporting
Gross real estate	100,106	39,829	100,106	39,829
Non-allocated
Segment Reporting
Total revenue	808	299	1,685	690
Gross real estate	322,576	407,361	322,576	407,361
Continuing Operations
Segment Reporting
Total revenue	554,024	555,006	1,095,572	1,133,527
Continuing Operations | Operating Segments | Established
Segment Reporting
Total revenue	500,641	522,697	997,140	1,068,983
Continuing Operations | Operating Segments | Other Stabilized
Segment Reporting
Total revenue	29,499	24,642	56,264	49,673
Continuing Operations | Non-allocated
Segment Reporting
Total revenue	$ 808	$ 299	$ 1,685	$ 690

Stock-Based Compensation Plan_2

Stock-Based Compensation Plans (Details 2) - $ / shares	6 Months Ended
	Jun. 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)
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)	(240)
Equity instruments outstanding at the end of the period (in shares)	285,700
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)	208.35
Equity instruments outstanding at the end of the period (in dollars per share)	$ 206.06
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%
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
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value	$ 28.64
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Term	5 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%
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	302,924	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 Arrangements by Share-based Payment Award, Options, Grants in Period, Weighted Average Exercise Price	$ 180.32
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross	294,115
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, Forfeitures in Period	(1,571)
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price	$ 178.63	$ 129.35
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Weighted Average Exercise Price	130.90
Share-based Compensation Arrangements by Share-based Payment Award, Options, Exercises in Period, Weighted Average Exercise Price	$ 121.78
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

Stock-Based Compensation Plan_3

Stock-Based Compensation Plans Stock-Based Compensation Plans (Details 3) - Performance Shares	6 Months Ended
	Jun. 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	6 Months Ended
	Jun. 30, 2021	Jun. 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)	94,641	68,209
Vested (in shares)	(66,038)
Forfeited (in shares)	(709)
Equity instruments outstanding at the end of the period (in shares)	159,618
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)	176.32
Vested (in dollars per share)	192.17
Forfeited (in dollars per share)	197.01
Equity instruments outstanding at the end of the period (in dollars per share)	$ 191.92
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)	(71,535)
Forfeited (in shares)	0
Equity instruments outstanding at the end of the period (in shares)	74,784

Stock-Based Compensation Plan_5

Stock-Based Compensation Plans (Details 5) - USD ($) $ / shares in Units, $ in Thousands	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020
Additional disclosures
Stock-based compensation expense	$ 12,897	$ 11,624
Capitalized stock-based compensation cost	$ 4,599	$ 6,174
Performance Shares
Additional disclosures
Grant date value (in dollars per share)	$ 178.38
Restricted stock and restricted stock units
Additional disclosures
Weighted average period for recognition of unrecognized compensation cost	2 years 1 month 6 days
Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount	$ 57,078

Related Party Arrangements (Det

Related Party Arrangements (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Related Party Arrangements
Management, development and other fees	$ 808	$ 926	$ 1,685	$ 1,933
Compensation expense			12,897	11,624
Unconsolidated real estate entities
Related Party Arrangements
Outstanding receivables	3,199		3,199		$ 5,408
Non Employee Director | Restricted stock and deferred stock awards
Related Party Arrangements
Compensation expense	476	$ 446	941	$ 901
Amount of deferred compensation	$ 1,543		$ 1,543		$ 614

Fair Value (Details)

Fair Value (Details)	3 Months Ended	6 Months Ended		12 Months Ended
	Jun. 30, 2021USD ($)derivative	Jun. 30, 2021USD ($)derivative	Jun. 30, 2020USD ($)	Dec. 31, 2020USD ($)
Derivative instruments and Hedging Activities
Derivative, Notional Amounts Settled During Period		$ 150,000,000
Receipt (payment) for termination of forward interest rate swaps		6,962,000	$ (25,135,000)
Unrealized gain on terminated cash flow hedges		(2,654,000)	$ 0	$ 2,894,000
Interest Rate Swap | Cash Flow Hedges
Derivative instruments and Hedging Activities
Derivative, Notional Amount	$ 150,000,000	$ 150,000,000
Derivative, Notional Amounts Entered Into During Period	$ 150,000,000
Derivative, average cap interest rate	1.50%	1.50%
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		$ 9,467,000
Not Designated as Hedging Instrument
Derivative instruments and Hedging Activities
Number of derivative instruments held | derivative	5	5
Not Designated as Hedging Instrument | Interest Rate Cap
Derivative instruments and Hedging Activities
Derivative, Notional Amount	$ 410,950,000	$ 410,950,000
Derivative, average cap interest rate	6.10%	6.10%

Fair Value Fair Value (Details

Fair Value Fair Value (Details 2) $ in Thousands	Jun. 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	1.50%

Fair Value (Details 3)

Fair Value (Details 3) - USD ($) $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2021	Mar. 31, 2021	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2021	Jun. 30, 2020
Fair Value Disclosures [Abstract]
Cash flow hedge losses reclassified to earnings	$ (2,366)	$ (2,367)	$ (2,301)	$ (1,949)	$ (4,733)	$ (4,250)

Fair Value (Details 4)

Fair Value (Details 4) - Recurring basis - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Estimate of Fair Value Measurement
Financial Instruments Measured/Discussed at Fair Value
DownREIT units	$ (1,565)	$ (1,203)
Total	(8,071,017)	(8,312,664)
Unsecured notes | Estimate of Fair Value Measurement
Financial Instruments Measured/Discussed at Fair Value
Indebtedness	(7,061,205)	(7,271,799)
Secured Debt and Variable Rate Unsecured Indebtedness | Estimate of Fair Value Measurement
Financial Instruments Measured/Discussed at Fair Value
Indebtedness	(1,007,522)	(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	97	6
Interest Rate Swap | Cash Flow Hedges | Estimate of Fair Value Measurement
Financial Instruments Measured/Discussed at Fair Value
Derivative assets	88	4,308
Derivative liability	(910)
Fair Value, Inputs, Level 1
Financial Instruments Measured/Discussed at Fair Value
DownREIT units	(1,565)	(1,203)
Total	(7,062,770)	(7,273,002)
Fair Value, Inputs, Level 1 | Unsecured notes
Financial Instruments Measured/Discussed at Fair Value
Indebtedness	(7,061,205)	(7,271,799)
Fair Value, Inputs, Level 2
Financial Instruments Measured/Discussed at Fair Value
Total	(1,008,247)	(1,039,662)
Fair Value, Inputs, Level 2 | Secured Debt and Variable Rate Unsecured Indebtedness
Financial Instruments Measured/Discussed at Fair Value
Indebtedness	(1,007,522)	(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	97	6
Fair Value, Inputs, Level 2 | Interest Rate Swap | Cash Flow Hedges
Financial Instruments Measured/Discussed at Fair Value
Derivative assets	88	4,308
Derivative liability	(910)
Fair Value, Inputs, Level 3
Financial Instruments Measured/Discussed at Fair Value
Total	$ 0	$ 0

Subsequent Events (Details)

Subsequent Events (Details)	6 Months Ended
	Jun. 30, 2021
Subsequent Events [Abstract]
Subsequent Events	Subsequent EventsThe 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 did not identify any items for disclosure.