AvalonBay Communities (AVB) 10-Q 4 Nov 16 2016 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2016	Oct. 31, 2016
Document and Entity Information
Entity Registrant Name	AVALONBAY COMMUNITIES INC
Entity Central Index Key	915,912
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Document Type	10-Q
Document Period End Date	Sep. 30, 2016
Document Fiscal Year Focus	2,016
Document Fiscal Period Focus	Q3
Amendment Flag	false
Entity Common Stock, Shares Outstanding		137,325,877

CONDENSED CONSOLIDATED BALANCE

CONDENSED CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Real estate:
Land and improvements	$ 3,894,647	$ 3,636,761
Buildings and improvements	13,993,232	13,056,292
Furniture, fixtures and equipment	515,887	458,224
Gross operating real estate	18,403,766	17,151,277
Less accumulated depreciation	(3,591,604)	(3,303,751)
Net operating real estate	14,812,162	13,847,526
Construction in progress, including land	1,439,271	1,592,917
Land held for development	519,626	484,377
Real estate assets held for sale, net	100,351	17,489
Real Estate Investments, Net	16,871,410	15,942,309
Cash and cash equivalents	65,899	400,507
Cash in escrow	166,289	104,821
Resident security deposits	32,640	30,077
Investments in unconsolidated real estate entities	176,882	216,919
Deferred development costs	46,188	37,577
Prepaid expenses and other assets	229,349	199,095
Total assets	17,588,657	16,931,305
LIABILITIES AND EQUITY
Unsecured notes, net	4,070,247	3,845,674
Variable rate unsecured credit facility	170,000	0
Mortgage notes payable, net	2,575,723	2,611,274
Dividends payable	185,384	171,257
Payables for construction	100,113	98,802
Accrued expenses and other liabilities	335,249	260,005
Accrued interest payable	44,027	40,085
Resident security deposits	57,495	53,132
Liabilities related to real estate assets held for sale	3,845	553
Total liabilities	7,542,083	7,080,782
Commitments and contingencies
Redeemable noncontrolling interests	9,950	9,997
Equity:
Preferred stock, $0.01 par value; $25 liquidation preference; 50,000,000 shares authorized at September 30, 2016 and December 31, 2015; zero shares issued and outstanding at September 30, 2016 and December 31, 2015	0	0
Common stock, $0.01 par value; 280,000,000 shares authorized at September 30, 2016 and December 31, 2015; 137,324,780 and 137,002,031 shares issued and outstanding at September 30, 2016 and December 31, 2015, respectively	1,373	1,370
Additional paid-in capital	10,099,739	10,068,532
Accumulated earnings less dividends	36,043	(197,989)
Accumulated other comprehensive loss	(100,531)	(31,387)
Total equity	10,036,624	9,840,526
Total liabilities and equity	$ 17,588,657	$ 16,931,305

CONDENSED CONSOLIDATED BALANCE3

CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) - $ / shares	Sep. 30, 2016	Dec. 31, 2015
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)	137,324,780	137,002,031
Common stock, shares outstanding (in shares)	137,324,780	137,002,031

CONDENSED CONSOLIDATED STATEMEN

CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Revenue:
Rental and other income	$ 514,891	$ 473,199	$ 1,522,705	$ 1,367,473
Management, development and other fees	1,320	2,161	4,310	7,714
Total revenue	516,211	475,360	1,527,015	1,375,187
Expenses:
Operating expenses, excluding property taxes	124,789	115,655	360,318	340,501
Property taxes	52,338	50,416	153,512	143,505
Interest expense, net	47,871	43,234	137,862	133,398
(Gain) loss on extinguishment of debt, net	0	(18,987)	2,461	(26,736)
Depreciation expense	131,729	120,184	391,414	355,664
General and administrative expense	11,928	10,464	35,343	31,266
Expensed acquisition, development and other pursuit costs, net of recoveries	3,804	3,391	8,702	5,251
Casualty and impairment loss (gain), net	0	(658)	3,935	10,668
Total expenses	372,459	325,015	1,085,677	972,181
Equity in (loss) income of unconsolidated real estate entities	(342)	20,554	54,779	68,925
Gain on sale of communities	202,163	35,216	284,582	106,151
Gain on sale of other real estate	10,778	0	10,921	9,647
Income before taxes	356,351	206,115	791,620	587,729
Income tax expense	22	39	95	1,348
Net income	356,329	206,076	791,525	586,381
Net loss attributable to noncontrolling interests	63	66	242	229
Net income attributable to common stockholders	356,392	206,142	791,767	586,610
Other comprehensive income (loss):
Income (loss) on cash flow hedges	719	(31)	(73,826)	(67)
Cash flow hedge losses reclassified to earnings	1,748	1,373	4,682	4,401
Comprehensive income	$ 358,859	$ 207,484	$ 722,623	$ 590,944
Earnings per common share - basic:
Net income attributable to common stockholders (in dollars per share)	$ 2.60	$ 1.54	$ 5.77	$ 4.42
Earnings per common share - diluted:
Net income attributable to common stockholders (in dollars per share)	2.59	1.53	5.76	4.39
Dividends per common share (in dollars per share)	$ 1.35	$ 1.25	$ 4.05	$ 3.75

CONDENSED CONSOLIDATED STATEME5

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015
Cash flows from operating activities:
Net income	$ 791,525	$ 586,381
Adjustments to reconcile net income to cash provided by operating activities:
Depreciation expense	391,414	355,664
Amortization of deferred financing costs	5,664	5,117
Amortization of debt premium	(14,146)	(19,571)
(Gain) loss on extinguishment of debt, net	2,461	(26,736)
Amortization of stock-based compensation	12,103	11,980
Equity in loss of, and return on, unconsolidated entities and noncontrolling interests, net of eliminations	11,756	13,502
Casualty and impairment (gain) loss, net	(3,935)	(17,303)
Abandonment of development pursuits	1,598	0
Cash flow hedge losses reclassified to earnings	4,682	4,334
Gain on sale of real estate assets	(348,675)	(146,745)
Increase in cash in operating escrows	(4,563)	(8,409)
(Increase) decrease in resident security deposits, prepaid expenses and other assets	(16,127)	2,986
Increase in accrued expenses, other liabilities and accrued interest payable	17,911	33,072
Net cash provided by operating activities	851,668	794,272
Cash flows from investing activities:
Development/redevelopment of real estate assets including land acquisitions and deferred development costs	(869,342)	(1,265,829)
Acquisition of real estate assets, including partnership interest	(393,916)	0
Capital expenditures - existing real estate assets	(43,020)	(40,358)
Capital expenditures - non-real estate assets	(5,513)	(4,887)
Proceeds from sale of real estate, net of selling costs	404,731	232,415
Increase in cash in deposit escrows	(59,263)	0
Insurance proceeds for property damage claims	17,196	44,142
Mortgage note receivable lending	(11,074)	0
Increase in payables for construction	1,311	1,010
Distributions from unconsolidated real estate entities	94,748	47,873
Investments in unconsolidated real estate entities	(2,449)	(881)
Net cash used in investing activities	(866,591)	(986,515)
Cash flows from financing activities:
Issuance of common stock, net	14,147	674,631
Dividends paid	(541,485)	(484,251)
Net borrowings under unsecured credit facility	170,000	0
Repayments of mortgage notes payable, including prepayment penalties	(161,095)	(743,653)
Issuance of unsecured notes	474,838	574,066
Repayment of unsecured notes	(250,000)	0
Payment of deferred financing costs	(10,910)	(4,741)
Payment for termination of forward interest rate swaps	(14,847)	0
Distributions to DownREIT partnership unitholders	(30)	(28)
Distributions to joint venture and profit-sharing partners	(303)	(274)
Redemption of preferred interest obligation	0	(14,410)
Net cash (used in) provided by financing activities	(319,685)	1,340
Net decrease in cash and cash equivalents	(334,608)	(190,903)
Cash and cash equivalents, beginning of period	400,507	509,460
Cash and cash equivalents, end of period	65,899	318,557
Cash paid during the period for interest, net of amount capitalized	$ 137,720	$ 149,097

CONDENSED CONSOLIDATED STATEME6

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Parenthetical) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015	Jan. 31, 2016	Dec. 31, 2015
Supplemental disclosures of non-cash investing and financing activities
Common stock issued through the dividend reinvestment plan (in shares)			1,689	1,608
Common stock issued through the dividend reinvestment plan			$ 304	$ 275
Number of shares withheld to satisfy employees' tax withholding and other liabilities (in shares)			53,214	39,800
Shares withheld to satisfy employees' tax withholding and other liabilities, value			$ 8,316	$ 5,921
Stock Issued During Period, Shares, Share-based Compensation, Forfeited (in shares)			407	4,293
Stock Issued During Period, Value, Share-based Compensation, Forfeited			$ 627	$ 502
Dividends declared but not paid	$ 185,384	$ 171,098	185,384	171,098		$ 171,257
Change in redemption value of redeemable noncontrolling interest			(529)
Increase (Decrease) in Prepaid Expense and Other Assets			(2,689)
Income (loss) on cash flow hedges	719	(31)	(73,826)	(67)
Increase in accrued expenses, other liabilities and accrued interest payable			53,591
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Net of Tax			(56,280)
Cash flow hedge losses reclassified to earnings	1,748	1,373	4,682	4,401
Impairment of Real Estate	0	$ 658	(3,935)	(10,668)
New England [Member]
Supplemental disclosures of non-cash investing and financing activities
Impairment of Real Estate				4,195
Avalon at Edgewater [Member]
Supplemental disclosures of non-cash investing and financing activities
Impairment of Real Estate			(8,702)	(15,663)
Avalon at Edgewater [Member] | New England [Member]
Supplemental disclosures of non-cash investing and financing activities
Impairment of Real Estate				$ 26,039
Mortgage notes payable | Notes Payable Maturities 2020 [Member] | Avalon Hoboken [Member]
Supplemental disclosures of non-cash investing and financing activities
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Noncurrent Liabilities, Long-term Debt					$ 67,904
Mortgage notes payable | Notes Payable Maturities 2019 [Member] | Avalon Columbia Pike [Member]
Supplemental disclosures of non-cash investing and financing activities
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Noncurrent Liabilities, Long-term Debt	$ 70,507		$ 70,507
Restricted Stock Converted From Performance Shares [Member]
Supplemental disclosures of non-cash investing and financing activities
Restricted stock granted (in shares)			115,618	95,826
Restricted stock
Supplemental disclosures of non-cash investing and financing activities
Restricted stock granted (in shares)			80,873	61,953
Fair value of shares issued			$ 13,129	$ 10,721
Stock Issued During Period, Shares, Share-based Compensation, Forfeited (in shares)			3,848
Restricted Stock and Restricted Stock Converted From Performance Shares [Member]
Supplemental disclosures of non-cash investing and financing activities
Restricted stock granted (in shares)			196,491	157,779
Retained Earnings [Member]
Supplemental disclosures of non-cash investing and financing activities
Change in redemption value of redeemable noncontrolling interest			$ (529)	$ 1,722
Deferred Compensation, Share-based Payments [Member] | Non Employee Director [Member]
Supplemental disclosures of non-cash investing and financing activities
Fair value of shares issued			$ 3,894	$ 3,552
Non Employee Director [Member] | Deferred Compensation, Share-based Payments [Member]
Supplemental disclosures of non-cash investing and financing activities
Restricted stock granted (in shares)			44,327	46,589

Organization, Basis of Presenta

Organization, Basis of Presentation and Significant Accounting Policies	9 Months Ended
	Sep. 30, 2016
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 primarily in New England, the New York/New Jersey metro area, the Mid-Atlantic, the Pacific Northwest, and Northern and Southern California. At September 30, 2016 , the Company owned or held a direct or indirect ownership interest in 261 operating apartment communities containing 75,254 apartment homes in 10 states and the District of Columbia, of which eight communities containing 3,363 apartment homes were under reconstruction. In addition, the Company owned or held a direct or indirect interest in 22 communities under construction that are expected to contain an aggregate of 7,454 apartment homes when completed. 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 28 communities that, if developed as expected, will contain an estimated 9,550 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 2015 Annual Report on Form 10-K. The results of operations for the three and nine months ended September 30, 2016 are not necessarily indicative of the operating results for the full year. Management believes the disclosures are adequate to ensure the information presented is not misleading. In the opinion of management, all adjustments and eliminations, consisting only of normal, recurring adjustments necessary for a fair presentation of the financial statements for the interim periods, have been included. Capitalized terms used without definition have meanings provided elsewhere in this Form 10-Q. Earnings per Common Share Basic earnings per share is computed by dividing net income attributable to common stockholders by the weighted average number of shares outstanding during the period. All outstanding unvested restricted share awards contain rights to non-forfeitable dividends and participate in undistributed earnings with common shareholders and, accordingly, are considered participating securities that are included in the two-class method of computing basic earnings per share (“EPS”). Both the unvested restricted shares and other potentially dilutive common shares, and the related impact to earnings, are considered when calculating earnings per share on a diluted basis. The Company’s earnings per common share are determined as follows (dollars in thousands, except per share data): For the three months ended For the nine months ended 9/30/2016 9/30/2015 9/30/2016 9/30/2015 Basic and diluted shares outstanding Weighted average common shares - basic 136,997,756 133,669,584 136,901,164 132,516,847 Weighted average DownREIT units outstanding 7,500 7,500 7,500 7,500 Effect of dilutive securities 499,798 1,032,376 533,642 1,139,423 Weighted average common shares - diluted 137,505,054 134,709,460 137,442,306 133,663,770 Calculation of Earnings per Share - basic Net income attributable to common stockholders $ 356,392 $ 206,142 $ 791,767 $ 586,610 Net income allocated to unvested restricted shares (872 ) (467 ) (2,036 ) (1,444 ) Net income attributable to common stockholders, adjusted $ 355,520 $ 205,675 $ 789,731 $ 585,166 Weighted average common shares - basic 136,997,756 133,669,584 136,901,164 132,516,847 Earnings per common share - basic $ 2.60 $ 1.54 $ 5.77 $ 4.42 Calculation of Earnings per Share - diluted Net income attributable to common stockholders $ 356,392 $ 206,142 $ 791,767 $ 586,610 Add: noncontrolling interests of DownREIT unitholders in consolidated partnerships, including discontinued operations 10 9 30 28 Adjusted net income available to common stockholders $ 356,402 $ 206,151 $ 791,797 $ 586,638 Weighted average common shares - diluted 137,505,054 134,709,460 137,442,306 133,663,770 Earnings per common share - diluted $ 2.59 $ 1.53 $ 5.76 $ 4.39 All options to purchase shares of common stock outstanding as of September 30, 2016 and 2015 are included in the computation of diluted earnings per share. The Company is required to estimate the forfeiture of stock options and recognize compensation cost net of the estimated forfeitures. The estimated forfeitures included in compensation cost are adjusted to reflect actual forfeitures at the end of the vesting period. The forfeiture rate at September 30, 2016 was 0.8% and is based on the average forfeiture activity over a period equal to the estimated life of the stock options. The application of estimated forfeitures did not materially impact compensation expense for the three and nine months ended September 30, 2016 or 2015 . 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 general and administrative expenses. 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 effective portion of cumulative changes in the fair value of Hedging Derivatives in other comprehensive income (loss). Amounts recorded in other comprehensive income (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 10, "Fair Value," for further discussion of derivative financial instruments. Legal and Other Contingencies In January 2015, a fire occurred at the Company's Avalon at Edgewater apartment community located in Edgewater, New Jersey. Edgewater consisted of two residential buildings. One building, containing 240 apartment homes, was destroyed. The second building, containing 168 apartment homes, suffered minimal damage and has been repaired. The Company has established protocols for processing claims from third parties who suffered losses as a result of the fire, and many third parties have contacted the Company's insurance carrier and settled their claims. See Part II, Item 1, "Legal Proceedings," for further discussion of the lawsuits associated with the Edgewater casualty loss. Three class action lawsuits have been filed against the Company on behalf of occupants of the destroyed building and consolidated in the United States District Court for the District of New Jersey. The Company has agreed with class counsel to the terms of a proposed settlement which would provide a claims process (with agreed upon protocols for instructing the adjuster as to how to evaluate claims) and, if needed, an arbitration process to determine damage amounts to be paid to individual claimants covered by the class settlement. On July 8, 2016, class counsel filed with the court a motion for preliminary approval of this class settlement, and the Company did not oppose such motion. The Court administratively terminated this motion without prejudice due to the filing of an appeal of an order denying a motion to intervene in the settlement, but the Company expects that the motion will be re-filed shortly. The Company cannot predict when or if the court will approve the settlement. A fourth class action, being heard in the same federal court, was filed against the Company on behalf of residents of the second Edgewater building that suffered minimal damage. In addition to the class action lawsuits described above, 20 lawsuits representing approximately 141 individual plaintiffs have been filed in the Superior Court of New Jersey Bergen County - Law Division and 19 of these lawsuits are currently pending. All of these state court cases have been consolidated by the court; the Company believes that it has meritorious defenses to the extent of damages claimed in all of the suits. There are also three subrogation lawsuits that have been filed against the Company by insurers of Edgewater residents who obtained “renter’s insurance”; it is the Company’s position that in the majority of the applicable leases the residents waived subrogation rights. One of these lawsuits has been dismissed on that basis and the other two are currently pending in the United States District Court for the District of New Jersey. Having settled many third party claims through the insurance claims process, the Company currently believes that any potential remaining liability to third parties (including any potential liability to third parties determined in accordance with the class settlement described above, if approved) will not be material to the Company and will in any event be substantially covered by the Company's insurance policies. However, the Company can give no assurances in this regard and continues to evaluate this matter. See Note 5, "Investments in Real Estate Entities," and Part II, Item 1, "Legal Proceedings," for further discussion of the casualty gains and losses and lawsuits associated with the Edgewater casualty loss. The Company is involved in various other claims and/or administrative proceedings unrelated to the Edgewater casualty loss 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 other outstanding litigation matters, individually or in the aggregate, will have a material adverse effect on its financial condition or results of operations. Acquisitions of Investments in Real Estate The Company accounts for acquisitions of investments in real estate in accordance with the authoritative guidance for the initial measurement, which requires the identifiable assets acquired, the liabilities assumed, and any noncontrolling interest in the acquiree to be recognized at fair value. Typical assets and liabilities acquired include land, building, furniture, fixtures, and equipment, debt and identified intangible assets and liabilities, consisting of the value of above or below market leases and in-place leases. In making estimates of fair values for purposes of allocating purchase price, the Company utilizes various sources, including its own analysis of recently acquired and existing comparable properties in its portfolio and other market data. Consideration for acquisitions is typically in the form of cash unless otherwise disclosed. 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 and disposition activity. Recently Issued Accounting Standards In May 2014, the FASB issued ASU 2014-09, Revenue from Contracts with Customers, a revenue recognition standard that will result in companies recognizing revenue from contracts when control for the service or product that is the subject of the contract is transferred from the seller to the buyer. In August 2015, the FASB issued ASU 2015-14, Revenue from Contracts with Customers-Deferral of the Effective Date, which defers the effective date of the new revenue recognition standard until the first quarter of 2018. Subsequently, the FASB has issued multiple ASU’s clarifying ASU 2014-09 and ASU 2015-14. The Company is assessing whether the new standard will have a material effect on its financial position or results of operations. In February 2016, the FASB issued ASU 2016-02, Leases, amending the existing accounting standards for lease accounting, including requiring lessees to recognize most leases on their balance sheets and making targeted changes to lessor accounting. The new standard requires a modified retrospective transition approach for all leases existing at, or entered into after, the date of initial application, with an option to use certain transition relief. The guidance will be effective in the first quarter of 2019 and allows for early adoption. The Company is assessing whether the new standard will have a material effect on its financial position or results of operations. In March 2016, the FASB issued ASU 2016-09, Compensation-Stock Compensation: Improvements to Employee Share-Based Payment Accounting, which simplifies several aspects of share-based payment transactions, including income tax consequences, classification of awards as equity or liability, statement of cash flows classification and policy election options for forfeitures. The new standard requires either a prospective, retrospective or modified retrospective approach depending on the amendment type. The guidance will be effective in the first quarter of 2017 and allows for early adoption. The Company is assessing whether the new standard will have a material effect on its financial position or results of operations. In August 2016, the FASB issued ASU 2016-15, Statement of Cash Flows (Topic 230): Classification of Certain Cash Receipts and Cash Payments. This ASU addresses eight specific cash flow issues including debt prepayment or debt extinguishment costs, proceeds from the settlement of insurance claims, distributions received from equity method investees and separately identifiable cash flows and application of the predominance principle. The new standard requires a retrospective approach. The guidance will be effective in the first quarter of 2018 and allows for early adoption. The Company is assessing whether the new standard will have a material effect on its financial position or results of operations.

Interest Capitalized

Interest Capitalized	9 Months Ended
	Sep. 30, 2016
Interest Capitalized
Interest Capitalized	Interest Capitalized The Company capitalizes interest during the development and redevelopment of real estate assets. Capitalized interest associated with the Company’s development or redevelopment activities totaled $19,889,000 and $20,356,000 for the three months ended September 30, 2016 and 2015 , respectively, and $60,522,000 and $59,186,000 for the nine months ended September 30, 2016 and 2015 , respectively.

Mortgage Notes Payable, Unsecur

Mortgage Notes Payable, Unsecured Notes and Credit Facility	9 Months Ended
	Sep. 30, 2016
Debt Disclosure [Abstract]
Notes Payable, Unsecured Notes and Credit Facility	Mortgage Notes Payable, Unsecured Notes and Credit Facility The Company’s mortgage notes payable, unsecured notes, variable rate unsecured term loan (the “Term Loan”) and Credit Facility, as defined below, as of September 30, 2016 and December 31, 2015 are summarized below (dollars in thousands). The following amounts and discussion do not include the mortgage notes related to the communities classified as held for sale, if any, as of September 30, 2016 and December 31, 2015 , as shown in the accompanying Condensed Consolidated Balance Sheets (dollars in thousands) (see Note 6, “Real Estate Disposition Activities”). 9/30/2016 12/31/2015 Fixed rate unsecured notes (1) $ 3,800,000 $ 3,575,000 Term Loan 300,000 300,000 Fixed rate mortgage notes payable - conventional and tax-exempt (2) 1,672,758 1,561,109 Variable rate mortgage notes payable - conventional and tax-exempt (2) 908,621 1,045,182 Total mortgage notes payable and unsecured notes 6,681,379 6,481,291 Credit Facility 170,000 — Total mortgage notes payable, unsecured notes and Credit Facility $ 6,851,379 $ 6,481,291 _____________________________________ (1) Balances at September 30, 2016 and December 31, 2015 exclude $6,882 and $7,601 , respectively, of debt discount, and $22,871 and $21,725 , respectively, of deferred financing costs, as reflected in unsecured notes, net on the accompanying Condensed Consolidated Balance Sheets. (2) Balances at September 30, 2016 and December 31, 2015 exclude $6,501 and $19,686 , respectively, of debt premium, and $12,157 and $14,703 , respectively, of deferred financing costs, as reflected in mortgage notes payable on the accompanying Condensed Consolidated Balance Sheets. The following debt activity occurred during the nine months ended September 30, 2016 : • In January 2016, in conjunction with the disposition of Eaves Trumbull, Avalon at Stratford was substituted as collateral for the outstanding fixed rate mortgage note secured by Eaves Trumbull. • In January 2016, in conjunction with the acquisition of Avalon Hoboken, the Company assumed a fixed rate secured mortgage note with a principal balance of $67,904,000 and a contractual interest rate of 4.18% maturing in December 2020 . • In February 2016, the Company repaid the $16,212,000 fixed rate mortgage note secured by Archstone Lexington, with an effective interest rate of 3.32% at par and without penalty in advance of its March 2016 maturity date. Upon repayment, Archstone Lexington was substituted as collateral for the outstanding fixed rate mortgage note secured by Avalon Walnut Ridge I. • In April 2016, the Company repaid $134,500,000 of variable rate debt secured by Avalon Walnut Creek at par in advance of its March 2046 maturity date, recognizing a non-cash charge of $2,461,000 for the write-off of deferred financing costs. • In May 2016, the Company issued $475,000,000 principal amount of unsecured notes in a public offering under its existing shelf registration statement for net proceeds of approximately $471,751,000 . The notes mature in May 2026 and were issued at a 2.95% coupon rate. The notes have an effective interest rate of approximately 3.35% , including the effect of an interest rate hedge and offering costs. • In August 2016, Avalon Wilshire, Avalon Mission Oaks and Avalon Encino were substituted as collateral for the outstanding fixed rate mortgage notes secured by Eaves Nanuet, Avalon Shrewsbury and Avalon at Freehold, respectively. • In September 2016, the Company repaid $250,000,000 principal amount of its 5.75% coupon unsecured notes pursuant to its scheduled maturity. • In September 2016, in conjunction with the acquisition of Avalon Columbia Pike, the Company assumed a fixed rate secured mortgage note with a principal balance of $70,507,000 and a contractual interest rate of 3.38% maturing in November 2019 . In January 2016, the Company extended the maturity of its revolving variable rate unsecured credit facility (the “Credit Facility”) from April 2017 to April 2020, and amended other provisions in the Credit Facility. In addition, pursuant to an option available under the terms of the Credit Facility, with the approval of the syndicate of lenders, the Company increased the aggregate facility size from $1,300,000,000 to $1,500,000,000 (the "Credit Facility Increase"). The Company may further extend the term for up to nine months , provided the Company is not in default and upon payment of a $1,500,000 extension fee. In connection with the Credit Facility Increase, the applicable margin over reference rates used to determine the applicable interest rates on the Company's borrowings from time to time decreased. The Credit Facility bears interest at varying levels based on the London Interbank Offered Rate ("LIBOR"), rating levels achieved on the Company's unsecured notes and on a maturity schedule selected by the Company. The current stated pricing is LIBOR plus 0.825% per annum ( 1.36% at September 30, 2016 ), assuming a one month borrowing rate. The stated spread over LIBOR can vary from LIBOR plus 0.80% to LIBOR plus 1.55% based on the Company's credit ratings. In addition, a competitive bid option is available for borrowings up to 65% of the Credit Facility amount, which allows banks that are part of the lender consortium to bid to make loans at a rate that is lower than the stated rate if market conditions allow. In connection with the Credit Facility Increase, the annual facility fee was also amended to lower the fee to 0.125% from 0.15% , resulting in a fee of approximately $1,875,000 annually based on the $1,500,000,000 facility size and based on the Company's current credit rating. The Company had $170,000,000 outstanding under the Credit Facility as of September 30, 2016 and no borrowings outstanding under the Credit Facility as of December 31, 2015 . The Company had $53,137,000 and $43,049,000 outstanding in letters of credit that reduced the borrowing capacity as of September 30, 2016 and December 31, 2015 , respectively. In the aggregate, secured notes payable mature at various dates from February 2017 through July 2066, and are secured by certain apartment communities (with a net carrying value of $3,482,680,000 , excluding communities classified as held for sale, as of September 30, 2016 ). As of September 30, 2016 , the Company has guaranteed $100,000,000 of mortgage notes payable held by wholly-owned subsidiaries; all such mortgage notes payable are consolidated for financial reporting purposes. The weighted average interest rate of the Company’s fixed rate mortgage notes payable (conventional and tax-exempt) was 4.4% and 4.6% at September 30, 2016 and December 31, 2015 , respectively. The weighted average interest rate of the Company’s variable rate mortgage notes payable (conventional and tax-exempt), the Term Loan and its Credit Facility, including the effect of certain financing related fees, was 2.3% and 1.8% at September 30, 2016 and December 31, 2015 , respectively. Scheduled payments and maturities of mortgage notes payable and unsecured notes outstanding at September 30, 2016 are as follows (dollars in thousands): Year Secured notes payments Secured notes maturities Unsecured notes maturities Stated interest rate of unsecured notes 2016 $ 4,536 $ — $ — N/A 2017 18,671 709,591 250,000 5.700 % 2018 17,793 76,669 — N/A 2019 4,696 655,386 — N/A 2020 3,624 118,729 250,000 6.100 % 400,000 3.625 % 2021 3,551 27,844 250,000 3.950 % 300,000 LIBOR + 1.450% 2022 3,795 — 450,000 2.950 % 2023 4,040 — 350,000 4.200 % 250,000 2.850 % 2024 4,310 — 300,000 3.500 % 2025 4,585 84,835 525,000 3.450 % 300,000 3.500 % Thereafter 218,644 620,080 475,000 2.950 % $ 288,245 $ 2,293,134 $ 4,100,000 The Company was in compliance at September 30, 2016 with customary financial and other covenants under the Credit Facility, the Term Loan, and the Company’s fixed rate unsecured notes.

Equity

Equity	9 Months Ended
	Sep. 30, 2016
Stockholders' Equity Note [Abstract]
Equity	Equity The following summarizes the changes in equity for the nine months ended September 30, 2016 (dollars in thousands): Common stock Additional paid-in capital Accumulated earnings less dividends Accumulated other comprehensive loss Total equity Balance at December 31, 2015 $ 1,370 $ 10,068,532 $ (197,989 ) $ (31,387 ) $ 9,840,526 Net income attributable to common stockholders — — 791,767 — 791,767 Loss on cash flow hedges — — — (73,826 ) (73,826 ) Cash flow hedge loss reclassified to earnings — — — 4,682 4,682 Change in redemption value of redeemable noncontrolling interest — — (529 ) — (529 ) Dividends declared to common stockholders — — (555,916 ) — (555,916 ) Issuance of common stock, net of withholdings 3 11,148 (1,290 ) — 9,861 Amortization of deferred compensation — 20,059 — — 20,059 Balance at September 30, 2016 $ 1,373 $ 10,099,739 $ 36,043 $ (100,531 ) $ 10,036,624 As of September 30, 2016 and December 31, 2015 , the Company’s charter had authorized for issuance a total of 280,000,000 shares of common stock and 50,000,000 shares of preferred stock. During the nine months ended September 30, 2016 , the Company: i. issued 128,192 shares of common stock in connection with stock options exercised; ii. issued 1,689 common shares through the Company’s dividend reinvestment plan; iii. issued 196,491 common shares in connection with restricted stock grants and the conversion of performance awards to restricted shares; iv. issued 44,327 common shares in conjunction with the conversion of deferred stock awards; v. withheld 53,214 common shares to satisfy employees’ tax withholding and other liabilities; vi. issued 5,671 common shares through the Employee Stock Purchase Program; and vii. canceled 407 common shares of restricted stock upon forfeiture. Any deferred compensation related to the Company’s stock option, restricted stock and performance award grants during the nine months ended September 30, 2016 is not reflected on the accompanying Condensed Consolidated Balance Sheet as of September 30, 2016 , and will not be reflected until recognized as compensation cost. In December 2015, the Company commenced a fourth continuous equity program ("CEP IV") under which the Company may sell 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 IV, the Company engaged sales agents who will receive compensation of up to 2.0% of the gross sales price for shares sold. CEP IV also allows the Company to enter into forward sale agreements up to $1,000,000,000 in aggregate sales price of its common stock. The Company expects that 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 2.0% of the sales prices of all borrowed shares of common stock sold. During the three and nine months ended September 30, 2016 , the Company had no sales under the program and did not enter into any forward sale agreements.

Investments in Real Estate Enti

Investments in Real Estate Entities	9 Months Ended
	Sep. 30, 2016
Equity Method Investments and Joint Ventures [Abstract]
Investments in Real Estate Entities	Investments in Real Estate Entities Investment in Unconsolidated Real Estate Entities As of September 30, 2016 , the Company had investments in five unconsolidated real estate entities with ownership interest percentages ranging from 20.0% to 31.3% , excluding development joint ventures and joint ventures formed with Equity Residential as part of the Archstone acquisition. 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 nine months ended September 30, 2016 , AvalonBay Value Added Fund II, L.P. ("Fund II") sold two communities: • Eaves Rancho San Diego, located in El Cajon, CA, containing 676 apartment homes, was sold for $158,000,000 . The Company's share of the gain in accordance with GAAP for the disposition was $13,057,000 . • Eaves Tustin, located in Tustin, CA, containing 628 apartment homes, was sold for $163,550,000 . The Company's share of the gain in accordance with GAAP for the disposition was $23,547,000 . In conjunction with the disposition of these communities during the nine months ended September 30, 2016 , Fund II repaid $127,191,000 of secured indebtedness in advance of the scheduled maturity dates. This resulted in charges for prepayment penalties and write-offs of deferred financing costs, of which the Company's portion was $1,670,000 , which is reported as a reduction of equity in (loss) income of unconsolidated real estate entities on the accompanying Condensed Consolidated Statements of Comprehensive Income. The Company has an equity interest of 31.3% in Fund II, and upon achievement of a threshold return, the Company has a right to incentive distributions for its promoted interest representing 20.0% of further Fund II distributions, which is in addition to its share of the remaining 80.0% of distributions. During the nine months ended September 30, 2016 , the Company recognized income of $3,447,000 for its promoted interest, which is reported as a component of equity in (loss) income of unconsolidated real estate entities on the accompanying Condensed Consolidated Statements of Comprehensive Income. During the nine months ended September 30, 2016 , Archstone Multifamily Partners AC LP (the "U.S. Fund") sold two communities: • Archstone Boca Town Center, located in Boca Raton, FL, containing 252 apartment homes, was sold for $56,300,000 . The Company's share of the gain in accordance with GAAP for the disposition was $4,120,000 . • Avalon Kips Bay, located in New York, NY, containing 209 apartment homes, was sold for $173,000,000 . The Company's share of the gain in accordance with GAAP for the disposition was $12,448,000 . In conjunction with the disposition of these communities, during the nine months ended September 30, 2016 , the U.S. Fund repaid an aggregate of $94,822,000 of secured indebtedness in advance of the scheduled maturity dates. This resulted in charges for prepayment penalties and write-offs of deferred financing costs, of which the Company's aggregate portion was $2,003,000 , which is reported as a reduction of equity in (loss) income of unconsolidated real estate entities on the accompanying Condensed Consolidated Statements of Comprehensive Income. 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 (dollars in thousands): 9/30/2016 12/31/2015 (unaudited) (unaudited) Assets: Real estate, net $ 1,005,924 $ 1,392,833 Other assets 52,992 57,044 Total assets $ 1,058,916 $ 1,449,877 Liabilities and partners’ capital: Mortgage notes payable and credit facility $ 720,703 $ 947,205 Other liabilities 20,771 20,471 Partners’ capital 317,442 482,201 Total liabilities and partners’ capital $ 1,058,916 $ 1,449,877 The following is a combined summary of the operating results of the entities accounted for using the equity method discussed above for the periods presented (dollars in thousands): For the three months ended For the nine months ended 9/30/2016 9/30/2015 9/30/2016 9/30/2015 (unaudited) (unaudited) Rental and other income $ 30,771 $ 43,868 $ 101,534 $ 132,518 Operating and other expenses (12,069 ) (17,910 ) (39,206 ) (52,622 ) Gain on sale of communities — 66,410 180,256 98,899 Interest expense, net (1) (7,919 ) (14,883 ) (37,857 ) (35,694 ) Depreciation expense (8,081 ) (11,213 ) (26,027 ) (35,058 ) Net income $ 2,702 $ 66,272 $ 178,700 $ 108,043 _____________________________________ (1) Amount for the nine months ended September 30, 2016 includes charges for prepayment penalties and write-offs of deferred financing costs of $12,344 . In conjunction with the formation of Fund II, and the acquisition of the U.S. Fund, Multifamily Partners AC JV LP (the "AC JV") and Brandywine Apartments of Maryland, LLC ("Brandywine"), the Company incurred costs in excess of its equity in the underlying net assets of the respective investments. These costs represent $38,485,000 and $40,978,000 at September 30, 2016 and December 31, 2015 , respectively, of the Company's respective investment balances. These amounts are being amortized over the lives of the underlying assets as a component of equity in (loss) income of unconsolidated entities on the accompanying Condensed Consolidated Statements of Comprehensive Income. In May 2016, the Company entered into a joint venture agreement to facilitate the acquisition of Avalon Clarendon, located in Arlington, VA. Avalon Clarendon is part of a mixed-use development containing residential, retail, office and public parking. The Company contributed $120,300,000 to the venture for the Company's share of the purchase price. The Company had shared control of the overall venture with its partner, but had all of the rights and obligations associated with the residential component of Avalon Clarendon, containing 300 apartment homes. The joint venture partner had all of the rights and obligations associated with the retail, office and public parking components of the mixed-use development. During the three months ended September 30, 2016 , the Company and its venture partner established separate legal ownership of the residential and retail, office and public parking components of the venture, and the Company retained all of the rights and obligations associated with the residential component. After this legal separation, the Company will report the operating results of Avalon Clarendon as part of its consolidated operations. In conjunction with the consolidation of Avalon Clarendon, the Company recorded the consolidated assets at fair value applying the framework discussed below under "Investments in Consolidated Real Estate Entities" for valuation, resulting in a gain of $4,322,000 for the difference between the fair value of Avalon Clarendon and the Company's equity interest at the date of consolidation of $115,848,000 , primarily attributable to depreciation recognized during the period the community was owned in the joint venture. The Company has included this gain as a component of gain on sale of communities on the accompanying Condensed Consolidated Statements of Comprehensive Income. During the three months ended September 30, 2016 , the Company entered into a joint venture to develop, own, and operate AVA North Point, an apartment community located in Cambridge, MA, which is currently under construction and expected to contain 265 apartment homes upon completion. The Company owns a 55.0% interest in the venture, and the venture partner owns the remaining 45.0% interest. AVA North Point is the third phase of a master planned development, the other phases of which are owned through the AC JV. The AC JV’s partnership agreement contains provisions that require the Company to provide a right of first offer (“ROFO”) to the venture partners in connection with opportunities to acquire or develop additional interests in multifamily real estate assets within a specified geographic radius of the AC JV’s existing assets, generally one mile or less. During the three months ended September 30, 2016 , the Company provided the partners of the AC JV the opportunity to acquire the AVA North Point land parcel owned by the Company as required in the ROFO provisions for the AC JV. After certain partners of the AC JV declined to participate, the Company entered into the new joint venture and sold the land parcel to the venture in exchange for a cash payment and a capital account credit, and is overseeing the development in exchange for a developer fee. Upon sale of the land parcel, the Company recognized a gain of $10,621,000 , included in gain on sale of other real estate on the accompanying Condensed Consolidated Statements of Comprehensive Income. Investments in Consolidated Real Estate Entities During the nine months ended September 30, 2016 , in addition to Avalon Clarendon discussed above, the Company acquired four consolidated communities: • Avalon Hoboken, located in Hoboken, NJ, contains 217 apartment homes and was acquired for a purchase price of $129,700,000 . In conjunction with the acquisition, the Company assumed a fixed rate secured mortgage note with a principal balance of $67,904,000 and a contractual interest rate of 4.18% maturing in December 2020 . • Avalon Potomac Yard, located in Alexandria, VA, contains 323 apartment homes and was acquired for a purchase price of $108,250,000 . • Avalon Columbia Pike, located in Arlington, VA, contains 269 apartment homes and was acquired for a purchase price of $102,000,000 . In conjunction with the acquisition, the Company assumed a fixed rate secured mortgage note with a principal balance of $70,507,000 and a contractual interest rate of 3.38% maturing in November 2019 . • Studio 77, located in North Hollywood, CA, contains 156 apartment homes and was acquired for a purchase price of $72,100,000 . The Company accounted for these acquisitions as business combinations and recorded the acquired assets and assumed liabilities, including identifiable intangibles, at their fair values. The Company used third party pricing or internal models for the values of the land, a valuation model for the values of the buildings and debt, and an internal model to determine the fair values 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 Acquisition, Development and Other Pursuit Costs and Impairment of Long-Lived Assets 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 capitalized pre-development costs are expensed. The Company expensed costs related to the abandonment of Development Rights as well as costs incurred in pursuing the acquisition of assets or costs incurred pursuing the disposition of assets for which such disposition activity did not occur, in the amounts of $3,804,000 and $3,391,000 for the three months ended September 30, 2016 and 2015 , respectively, and $7,086,000 and $5,251,000 for the nine months ended September 30, 2016 and 2015 , respectively. These costs are included in expensed acquisition, 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. 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 for the three and nine months ended September 30, 2016 and 2015 , the Company did not recognize any impairment losses for wholly-owned operating real estate assets. 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 nine months ended September 30, 2016 , the Company recognized $10,500,000 of aggregate impairment charges related to three ancillary land parcels. This charge was determined as the excess of the Company's carrying basis over the expected sales price for each parcel, and is included in casualty and impairment loss (gain), net on the accompanying Condensed Consolidated Statements of Comprehensive Income. The Company did not recognize any material impairment charges on its investment in land during the three and nine months ended September 30, 2015 . 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 material other than temporary impairment losses recognized by any of the Company’s investments in unconsolidated real estate entities during the three and nine months ended September 30, 2016 and 2015 . Casualty Gains and Losses During the nine months ended September 30, 2016 , the Company reached a final insurance settlement for the Company's property damage and lost income for the Edgewater casualty loss, for which it received aggregate insurance proceeds for Edgewater of $73,150,000 , after self-insurance and deductibles, as discussed below. During the nine months ended September 30, 2015 , the Company received $44,142,000 in insurance proceeds, which were partially offset by casualty charges of $21,844,000 to write off the net book value of the building destroyed by the fire at Edgewater, and $6,635,000 to record demolition and additional incident expenses, resulting in a net casualty gain of $15,663,000 . Of these amounts, during the three months ended September 30, 2015 , the Company recorded casualty charges for additional demolition and incident costs related to Edgewater of $658,000 . During the nine months ended September 30, 2016 , the Company received the final $29,008,000 of insurance proceeds, of which $8,702,000 was recognized as an additional net casualty gain and $20,306,000 as business interruption insurance proceeds. The Company reported the net casualty gains from each of the respective reporting periods as casualty and impairment loss (gain), net on the accompanying Condensed Consolidated Statements of Comprehensive Income, and reported the business interruption insurance proceeds as a component of rental and other income on the accompanying Condensed Consolidated Statements of Comprehensive Income. See discussion in Note 1, "Organization, Basis of Presentation and Significant Accounting Policies, Legal and Other Contingencies," and Part II, Item 1, "Legal Proceedings," for further discussion of the Edgewater casualty loss. During the nine months ended September 30, 2015 , several of the Company's communities in its Northeast markets incurred property and casualty damages from severe winter storms, for which the Company recorded an impairment due to a casualty loss of $4,195,000 . During the nine months ended September 30, 2016 , the Company recorded a net casualty gain related to the 2015 severe winter storms of $5,732,000 , which is comprised of $8,493,000 in third-party insurance proceeds received, partially offset by incremental costs of $2,761,000 . These amounts are included in casualty and impairment loss (gain), net on the accompanying Condensed Consolidated Statements of Comprehensive Income.

Real Estate Disposition Activit

Real Estate Disposition Activities	9 Months Ended
	Sep. 30, 2016
Discontinued Operations and Disposal Groups [Abstract]
Real Estate Disposition Activities	Real Estate Disposition Activities During the nine months ended September 30, 2016 , the Company sold five wholly-owned operating communities. • Eaves Trumbull, located in Trumbull, CT, containing 340 homes, was sold for $70,250,000 . The Company's gain in accordance with GAAP on the disposition was $51,430,000 , reported in gain on sale of communities on the accompanying Condensed Consolidated Statements of Comprehensive Income. • Avalon Essex, located in Peabody, MA, containing 154 homes, was sold for $45,100,000 . The Company's gain in accordance with GAAP on the disposition was $31,081,000 , reported in gain on sale of communities on the accompanying Condensed Consolidated Statements of Comprehensive Income. • Eaves Nanuet, located in Nanuet, NY, containing 504 homes, was sold for $147,000,000 . The Company's gain in accordance with GAAP on the disposition was $118,008,000 , reported in gain on sale of communities on the accompanying Condensed Consolidated Statements of Comprehensive Income. • Avalon Shrewsbury, located in Shrewsbury, MA, containing 251 homes, was sold for $60,500,000 . The Company's gain in accordance with GAAP on the disposition was $33,350,000 , reported in gain on sale of communities on the accompanying Condensed Consolidated Statements of Comprehensive Income. The sale of Avalon Shrewsbury was expected to be part of a tax deferred exchange under which the Company had restricted the cash proceeds in an escrow account, classified as cash in escrow on the accompanying Condensed Consolidated Balance Sheet. These proceeds will be available to the Company as unrestricted cash in the fourth quarter of 2016. • Avalon at Freehold, located in Freehold, NJ, containing 296 homes, was sold for $68,000,000 . The Company's gain in accordance with GAAP on the disposition was $46,482,000 , reported in gain on sale of communities on the accompanying Condensed Consolidated Statements of Comprehensive Income. At September 30, 2016 , the Company had three communities and three ancillary land parcels that qualified as held for sale.

Segment Reporting

Segment Reporting	9 Months Ended
	Sep. 30, 2016
Segment Reporting [Abstract]
Segment Reporting	Segment Reporting The Company’s reportable operating segments include Established Communities, Other Stabilized Communities, and Development/Redevelopment Communities. 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 is comprised of several members of its executive management team who use net operating income (“NOI”) as the primary financial measure for Established 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, investments and investment management expenses, expensed acquisition, development and other pursuit costs, net of recoveries, interest expense, net, (gain) loss on extinguishment of debt, net, general and administrative expense, equity in (loss) income of unconsolidated real estate entities, depreciation expense, corporate income tax expense, casualty and impairment loss (gain), net, gain on sale of real estate assets and net operating income from real estate assets sold or held for sale. Although the Company considers NOI a useful measure of a community's or communities' operating performance, NOI should not be considered an alternative to net income or net cash flow from operating activities, as determined in accordance with GAAP. NOI excludes a number of income and expense categories as detailed in the reconciliation of NOI to net income. A reconciliation of NOI to net income for the three and nine months ended September 30, 2016 and 2015 is as follows (dollars in thousands): For the three months ended For the nine months ended 9/30/2016 9/30/2015 9/30/2016 9/30/2015 Net income $ 356,329 $ 206,076 $ 791,525 $ 586,381 Indirect operating expenses, net of corporate income 14,946 13,427 46,960 43,642 Investments and investment management expense 1,205 1,167 3,545 3,274 Expensed acquisition, development and other pursuit costs, net of recoveries 3,804 3,391 8,702 5,251 Interest expense, net 47,871 43,234 137,862 133,398 (Gain) loss on extinguishment of debt, net — (18,987 ) 2,461 (26,736 ) General and administrative expense 11,928 10,464 35,343 31,266 Equity in loss (income) of unconsolidated real estate entities 342 (20,554 ) (54,779 ) (68,925 ) Depreciation expense 131,729 120,184 391,414 355,664 Income tax expense 22 39 95 1,348 Casualty and impairment loss (gain), net — 658 (3,935 ) (10,668 ) Gain on sale of real estate (212,941 ) (35,216 ) (295,503 ) (115,798 ) Net operating income from real estate assets sold or held for sale (1) (5,525 ) (9,180 ) (19,751 ) (28,248 ) Net operating income $ 349,710 $ 314,703 $ 1,043,939 $ 909,849 __________________________________ (1) Represents NOI from real estate assets sold or held for sale as of September 30, 2016 that are not otherwise classified as discontinued operations. The following is a summary of NOI from real estate assets sold or held for sale for the periods presented (dollars in thousands): For the three months ended For the nine months ended 9/30/2016 9/30/2015 9/30/2016 9/30/2015 Rental income from real estate assets sold or held for sale $ 8,814 $ 15,098 $ 31,731 $ 46,610 Operating expenses from real estate assets sold or held for sale (3,289 ) (5,918 ) (11,980 ) (18,362 ) Net operating income from real estate assets sold or held for sale $ 5,525 $ 9,180 $ 19,751 $ 28,248 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 the beginning of the given calendar year. Therefore, each year the composition of communities within each business segment is adjusted. Accordingly, the amounts between years are not directly comparable. Segment information for total revenue and NOI for the three and nine months ended September 30, 2016 and 2015 has been adjusted to exclude the real estate assets that were sold from January 1, 2015 through September 30, 2016 , or otherwise qualify as held for sale as of September 30, 2016 , as described in Note 6, “Real Estate Disposition Activities.” Segment information for gross real estate as of September 30, 2016 and 2015 has not been adjusted to exclude real estate assets that were sold or otherwise qualified as held for sale subsequent to the respective balance sheet dates. For the three months ended For the nine months ended Total NOI % NOI change from prior year Total NOI % NOI change from prior year Gross real estate (1) For the period ended September 30, 2016 Established New England $ 59,321 $ 37,657 0.6 % $ 174,731 $ 111,497 5.9 % $ 1,845,679 Metro NY/NJ 96,231 65,299 1.5 % 283,554 193,001 2.0 % 3,206,696 Mid-Atlantic 58,929 40,029 0.4 % 174,922 120,623 1.4 % 2,335,116 Pacific Northwest 20,216 14,502 9.5 % 59,333 42,753 6.6 % 736,377 Northern California 80,783 61,560 5.9 % 238,867 182,658 8.0 % 2,657,020 Southern California 73,570 52,527 11.1 % 217,686 155,242 10.3 % 2,667,875 Total Established 389,050 271,574 4.3 % 1,149,093 805,774 5.5 % 13,448,763 Other Stabilized (2) 53,905 34,812 N/A 177,016 125,017 N/A 2,325,539 Development / Redevelopment 63,122 43,324 N/A 164,865 113,148 N/A 3,994,361 Land Held for Future Development N/A N/A N/A N/A N/A N/A 519,626 Non-allocated (3) 1,320 N/A N/A 4,310 N/A N/A 74,374 Total $ 507,397 $ 349,710 11.1 % $ 1,495,284 $ 1,043,939 14.7 % $ 20,362,663 For the period ended September 30, 2015 Established New England $ 45,245 $ 29,036 3.4 % $ 132,054 $ 81,883 0.8 % $ 1,487,944 Metro NY/NJ 92,153 65,207 3.8 % 270,406 190,735 3.1 % 3,196,771 Mid-Atlantic 52,839 36,157 0.3 % 156,806 108,125 (0.4 )% 2,172,951 Pacific Northwest 17,319 12,077 5.0 % 50,563 36,214 8.0 % 720,223 Northern California 69,850 53,095 9.5 % 202,508 155,464 10.8 % 2,412,264 Southern California 65,019 43,714 7.9 % 190,513 130,278 9.1 % 2,505,625 Total Established 342,425 239,286 5.2 % 1,002,850 702,699 5.2 % 12,495,778 Other Stabilized 56,564 36,949 N/A 165,319 108,355 N/A 2,106,947 Development / Redevelopment 59,112 38,468 N/A 152,694 98,795 N/A 3,795,868 Land Held for Future Development N/A N/A N/A N/A N/A N/A 553,729 Non-allocated (3) 2,161 N/A N/A 7,714 N/A N/A 50,556 Total $ 460,262 $ 314,703 11.5 % $ 1,328,577 $ 909,849 12.8 % $ 19,002,878 __________________________________ (1) Does not include gross real estate assets held for sale of $135,054 as of September 30, 2016 . (2) Total revenue and NOI for the nine months ended September 30, 2016 includes $20,306 in business interruption insurance proceeds related to the Edgewater casualty loss. (3) Revenue represents third-party management, asset management and developer fees and miscellaneous income which are not allocated to a reportable segment.

Stock-Based Compensation Plans

Stock-Based Compensation Plans	9 Months Ended
	Sep. 30, 2016
Disclosure of Compensation Related Costs, Share-based Payments [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. Detail of the outstanding awards and activity is presented below. Information with respect to stock options granted under the Company’s 1994 Stock Option and Incentive Plan (the “1994 Plan”) and its 2009 Stock Option and Incentive Plan (the “2009 Plan”) is as follows: 2009 Plan shares Weighted average exercise price per share 1994 Plan shares Weighted average exercise price per share Options Outstanding, December 31, 2015 249,178 $ 122.17 82,195 $ 103.27 Exercised (68,538 ) 116.37 (59,654 ) 112.85 Forfeited — — — — Options Outstanding, September 30, 2016 (1) 180,640 $ 124.37 22,541 $ 77.91 __________________________________ (1) All options outstanding are exercisable as of September 30, 2016 . Information with respect to performance awards granted is as follows: Performance awards Weighted average grant date fair value per award Outstanding at December 31, 2015 238,266 $ 119.65 Granted (1) 94,054 141.92 Change in units based on performance (2) 36,091 101.52 Converted to restricted stock (115,618 ) 94.67 Forfeited (1,630 ) 141.98 Outstanding at September 30, 2016 251,163 $ 136.74 __________________________________ (1) The amount of restricted stock that ultimately may be earned is based on the total shareholder return metrics related to the Company’s common stock for 61,039 performance awards and financial metrics related to operating performance and leverage metrics of the Company for 33,015 performance awards. (2) Represents the change in the number of performance awards earned based on performance achievement. The Company used a Monte Carlo model to assess the compensation cost associated with the portion of the performance awards determined by using total shareholder return measures. The assumptions used are as follows: 2016 Dividend yield 3.3% Estimated volatility over the life of the plan (1) 15.2% - 22.8% Risk free rate 0.44% - 0.88% Estimated performance award value based on total shareholder return measure $131.24 __________________________________ (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 2016, for which achievement will be determined by using financial metrics, the compensation cost was based on a weighted average grant date value of $161.66 , 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, 2015 147,884 $ 146.21 98,347 Granted - restricted stock shares 80,873 162.34 115,618 Vested - restricted stock shares (84,623 ) 141.49 (36,872 ) Forfeited (3,453 ) 162.34 (395 ) Outstanding at September 30, 2016 140,681 $ 157.49 176,698 Total employee stock-based compensation cost recognized in income was $11,555,000 and $11,255,000 for the nine months ended September 30, 2016 and 2015 , respectively, and total capitalized stock-based compensation cost was $7,790,000 and $7,738,000 for the nine months ended September 30, 2016 and 2015 , respectively. At September 30, 2016 , there was a total unrecognized compensation cost of $28,890,000 for unvested restricted stock and performance awards, which does not include estimated forfeitures, and is expected to be recognized over a weighted average period of 3.6 years.

Related Party Arrangements

Related Party Arrangements	9 Months Ended
	Sep. 30, 2016
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 $1,320,000 and $2,161,000 during the three months ended September 30, 2016 and 2015 , respectively, and $4,310,000 and $7,714,000 for the nine months ended September 30, 2016 and 2015 , respectively. These fees are recognized on an accrual basis when earned in accordance with the accounting guidance applicable to revenue recognition, and are included in management, development and other fees on the accompanying Condensed Consolidated Statements of Comprehensive Income. In addition, the Company has outstanding receivables associated with its property and construction management role of $9,983,000 and $3,832,000 as of September 30, 2016 and December 31, 2015 , respectively. Director Compensation The Company recorded non-employee director compensation expense relating to restricted stock grants and deferred stock awards in the amount of $260,000 and $293,000 in the three months ended September 30, 2016 and 2015 , respectively, and $877,000 and $842,000 in the nine months ended September 30, 2016 and 2015 , respectively, as a component of general and administrative expense. Deferred compensation relating to these restricted stock grants and deferred stock awards to non-employee directors was $693,000 and $488,000 on September 30, 2016 and December 31, 2015 , respectively. During the nine months ended September 30, 2016 , the Company issued 44,327 shares of common stock in conjunction with the conversion of deferred stock awards.

Fair Value

Fair Value	9 Months Ended
	Sep. 30, 2016
Fair Value Disclosures [Abstract]
Fair Value	Fair Value Financial Instruments Carried at Fair Value Derivative Financial Instruments Currently, the Company uses interest rate swap and interest rate cap agreements to manage its interest rate risk. These instruments are carried at fair value in the Company’s financial statements. In adjusting the fair value of its derivative contracts for the effect of counterparty nonperformance risk, the Company has considered the impact of its net position with a given counterparty, as well as any applicable credit enhancements, such as collateral postings, thresholds, mutual puts, and guarantees. The Company minimizes its credit risk on these transactions by dealing with major, creditworthy financial institutions which have an A or better credit rating by the Standard & Poor’s Ratings Group. As part of its on-going control procedures, the Company monitors the credit ratings of counterparties and the exposure of the Company to any single entity, thus reducing credit risk concentration. The Company believes the likelihood of realizing losses from counterparty nonperformance is remote. Although the Company has determined that the majority of the inputs used to value its derivatives fall within Level 2 of the fair value hierarchy, such as interest rate, term to maturity and volatility, the credit valuation adjustments associated with its derivatives use Level 3 inputs, such as estimates of current credit spreads, to evaluate the likelihood of default by itself and its counterparties. As of September 30, 2016 , 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. Hedge ineffectiveness did not have a material impact on earnings of the Company for the three and nine months ended September 30, 2016 , or any prior period, and the Company does not anticipate that it will have a material effect in the future. The following table summarizes the consolidated derivative positions at September 30, 2016 (dollars in thousands): Non-designated Hedges Interest Rate Caps Cash Flow Hedges Interest Rate Caps Cash Flow Hedges Interest Rate Swaps Notional balance $ 722,943 $ 36,108 $ 800,000 Weighted average interest rate (1) 2.6 % 2.7 % N/A Weighted average swapped/capped interest rate 6.2 % 5.9 % 2.3 % Earliest maturity date Nov 2016 Apr 2019 Nov 2017 Latest maturity date Jul 2021 Apr 2019 Nov 2017 ____________________________________ (1) For interest rate caps, represents the weighted average interest rate on the hedged debt. During the nine months ended September 30, 2016 , the Company entered into $600,000,000 of forward interest rate swap agreements for a total of $1,200,000,000 of 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 2016 and 2017. In May 2016, the Company settled $400,000,000 of the aggregate outstanding swaps, as discussed below. For the remaining outstanding swaps, at maturity of the agreements, the Company expects to cash settle the contracts and either pay or receive cash for the then current fair value. Assuming that the Company issues the debt as expected, the impact from settling these positions will then be recognized over the life of the issued debt as a yield adjustment. In May 2016, in conjunction with the Company's May 2016 unsecured note issuance, the Company settled $400,000,000 of forward interest rate swap agreements designated as cash flow hedges of the interest rate variability on the forecasted issuance of the unsecured notes, making a payment of $14,847,000 . The Company has deferred the effective portion of the fair value change of these swaps in accumulated other comprehensive loss on the accompanying Condensed Consolidated Balance Sheets, and will recognize the impact as a component of interest expense, net, over the life of the unsecured notes. Excluding derivatives executed to hedge secured debt on communities classified as held for sale, the Company had 11 derivatives designated as cash flow hedges and 15 derivatives not designated as hedges at September 30, 2016 . Fair value changes for derivatives not in qualifying hedge relationships for the three and nine months ended September 30, 2016 and 2015 were not material. During nine months ended September 30, 2016 , the Company deferred $73,826,000 of losses for cash flow hedges reported as a component of other comprehensive income (loss). The following table summarizes the deferred losses reclassified from accumulated other comprehensive income as a component of interest expense, net (dollars in thousands): For the three months ended For the nine months ended 9/30/2016 9/30/2015 9/30/2016 9/30/2015 Cash flow hedge losses reclassified to earnings $ 1,748 $ 1,373 $ 4,682 $ 4,401 The Company anticipates reclassifying approximately $6,978,000 of hedging losses from accumulated other comprehensive loss into earnings within the next 12 months to offset the variability of cash flows of the hedged item during this period. Redeemable Noncontrolling Interests The Company provided redemption options (the “Puts”) that allow joint venture partners of the Company to require the Company to purchase their interests in the investment at a guaranteed minimum amount related to three ventures. The Puts are payable in cash. The Company determines the fair value of the Puts based on unobservable inputs considering the assumptions that market participants would make in pricing the obligations, applying a guaranteed rate of return to the joint venture partners’ net capital contribution balances as of period end. Given the significance of the unobservable inputs, the valuations are classified in Level 3 of the fair value hierarchy. The Company issued units of limited partnership interest in DownREITs which provide 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 agreements, 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 DownREITs 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 principal protected accounts. 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, accounts and construction payable and accrued expenses and other liabilities are carried at their face amounts, which reasonably approximate their fair values. The Company values its unsecured notes using quoted market prices, a Level 1 price within the fair value hierarchy. The Company values its notes payable and outstanding amounts under the Credit Facility and Term Loan 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 notes payable and amounts outstanding under its Credit Facility and Term Loan 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): Description Total Fair Value Quoted Prices (Level 1) Significant (Level 2) Significant (Level 3) 9/30/2016 Non-Designated Hedges Interest Rate Caps $ 16 $ — $ 16 $ — Cash Flow Hedges Interest Rate Caps — — — — Interest Rate Swaps (53,591 ) — (53,591 ) — Puts (8,181 ) — — (8,181 ) DownREIT units (1,334 ) (1,334 ) — — Indebtedness Unsecured notes (3,988,324 ) (3,988,324 ) — — Mortgage notes payable, Credit Facility and Term Loan (2,985,133 ) — (2,985,133 ) — Total $ (7,036,547 ) $ (3,989,658 ) $ (3,038,708 ) $ (8,181 ) Description Total Fair Value Quoted Prices (Level 1) Significant (Level 2) Significant (Level 3) 12/31/2015 Non-Designated Hedges Interest Rate Caps $ 26 $ — $ 26 $ — Cash Flow Hedges Interest Rate Caps 5 — 5 — Interest Rate Swaps 5,422 — 5,422 — Puts (8,181 ) — — (8,181 ) DownREIT units (1,381 ) (1,381 ) — — Indebtedness Unsecured notes (3,668,417 ) (3,668,417 ) — — Mortgage notes payable, Credit Facility and Term Loan (2,700,341 ) — (2,700,341 ) — Total $ (6,372,867 ) $ (3,669,798 ) $ (2,694,888 ) $ (8,181 )

Subsequent Events

Subsequent Events	9 Months Ended
	Sep. 30, 2016
Subsequent Events [Abstract]
Subsequent Events	Subsequent Events The Company has evaluated subsequent events through the date on which this Form 10-Q was filed, the date on which these financial statements were issued, and identified the items below for discussion. In October 2016, the Company issued the following unsecured notes in public offerings under its existing shelf registration statement. • $300,000,000 principal amount of unsecured notes were issued for net proceeds of approximately $297,117,000 . The notes mature in October 2026 and were issued at a 2.90% coupon interest rate. • $350,000,000 principal amount of unsecured notes were issued for net proceeds of approximately $345,520,000 . The notes mature in October 2046 and were issued at a 3.90% coupon interest rate. In October 2016, the Company issued a redemption notice for $250,000,000 principal amount of its 5.70% coupon unsecured notes in advance of the March 2017 scheduled maturity. The Company expects to complete the redemption of the unsecured notes in November 2016. In October 2016, the Company sold two wholly-owned communities. Avalon Brandemoor I and II, located in Lynnwood, WA, contain an aggregate of 506 apartment homes and were sold for $132,000,000 .

Organization, Basis of Presen18

Organization, Basis of Presentation and Significant Accounting Policies (Policies)	9 Months Ended
	Sep. 30, 2016
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 primarily in New England, the New York/New Jersey metro area, the Mid-Atlantic, the Pacific Northwest, and Northern and Southern California. At September 30, 2016 , the Company owned or held a direct or indirect ownership interest in 261 operating apartment communities containing 75,254 apartment homes in 10 states and the District of Columbia, of which eight communities containing 3,363 apartment homes were under reconstruction. In addition, the Company owned or held a direct or indirect interest in 22 communities under construction that are expected to contain an aggregate of 7,454 apartment homes when completed. 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 28 communities that, if developed as expected, will contain an estimated 9,550 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 2015 Annual Report on Form 10-K. The results of operations for the three and nine months ended September 30, 2016 are not necessarily indicative of the operating results for the full year. Management believes the disclosures are adequate to ensure the information presented is not misleading. In the opinion of management, all adjustments and eliminations, consisting only of normal, recurring adjustments necessary for a fair presentation of the financial statements for the interim periods, have been included. Capitalized terms used without definition have meanings provided elsewhere in this Form 10-Q.
Earnings per Common Share	Earnings per Common Share Basic earnings per share is computed by dividing net income attributable to common stockholders by the weighted average number of shares outstanding during the period. All outstanding unvested restricted share awards contain rights to non-forfeitable dividends and participate in undistributed earnings with common shareholders and, accordingly, are considered participating securities that are included in the two-class method of computing basic earnings per share (“EPS”). Both the unvested restricted shares and other potentially dilutive common shares, and the related impact to earnings, are considered when calculating earnings per share on a diluted basis. The Company’s earnings per common share are determined as follows (dollars in thousands, except per share data): For the three months ended For the nine months ended 9/30/2016 9/30/2015 9/30/2016 9/30/2015 Basic and diluted shares outstanding Weighted average common shares - basic 136,997,756 133,669,584 136,901,164 132,516,847 Weighted average DownREIT units outstanding 7,500 7,500 7,500 7,500 Effect of dilutive securities 499,798 1,032,376 533,642 1,139,423 Weighted average common shares - diluted 137,505,054 134,709,460 137,442,306 133,663,770 Calculation of Earnings per Share - basic Net income attributable to common stockholders $ 356,392 $ 206,142 $ 791,767 $ 586,610 Net income allocated to unvested restricted shares (872 ) (467 ) (2,036 ) (1,444 ) Net income attributable to common stockholders, adjusted $ 355,520 $ 205,675 $ 789,731 $ 585,166 Weighted average common shares - basic 136,997,756 133,669,584 136,901,164 132,516,847 Earnings per common share - basic $ 2.60 $ 1.54 $ 5.77 $ 4.42 Calculation of Earnings per Share - diluted Net income attributable to common stockholders $ 356,392 $ 206,142 $ 791,767 $ 586,610 Add: noncontrolling interests of DownREIT unitholders in consolidated partnerships, including discontinued operations 10 9 30 28 Adjusted net income available to common stockholders $ 356,402 $ 206,151 $ 791,797 $ 586,638 Weighted average common shares - diluted 137,505,054 134,709,460 137,442,306 133,663,770 Earnings per common share - diluted $ 2.59 $ 1.53 $ 5.76 $ 4.39 All options to purchase shares of common stock outstanding as of September 30, 2016 and 2015 are included in the computation of diluted earnings per share. The Company is required to estimate the forfeiture of stock options and recognize compensation cost net of the estimated forfeitures. The estimated forfeitures included in compensation cost are adjusted to reflect actual forfeitures at the end of the vesting period. The forfeiture rate at September 30, 2016 was 0.8% and is based on the average forfeiture activity over a period equal to the estimated life of the stock options. The application of estimated forfeitures did not materially impact compensation expense for the three and nine months ended September 30, 2016 or 2015 .
Derivative Instruments and Hedging Activities	Derivative Instruments and Hedging Activities The Company enters into interest rate swap and interest rate cap agreements (collectively, “Hedging Derivatives”) for interest rate risk management purposes and in conjunction with certain variable rate secured debt to satisfy lender requirements. The Company does not enter into Hedging Derivative transactions for trading or other speculative purposes. The Company assesses the effectiveness of qualifying cash flow and fair value hedges, both at inception and on an on-going basis. Hedge ineffectiveness is reported as a component of general and administrative expenses. 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 effective portion of cumulative changes in the fair value of Hedging Derivatives in other comprehensive income (loss). Amounts recorded in other comprehensive income (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.
Legal and Other Contingencies	Legal and Other Contingencies In January 2015, a fire occurred at the Company's Avalon at Edgewater apartment community located in Edgewater, New Jersey. Edgewater consisted of two residential buildings. One building, containing 240 apartment homes, was destroyed. The second building, containing 168 apartment homes, suffered minimal damage and has been repaired. The Company has established protocols for processing claims from third parties who suffered losses as a result of the fire, and many third parties have contacted the Company's insurance carrier and settled their claims. See Part II, Item 1, "Legal Proceedings," for further discussion of the lawsuits associated with the Edgewater casualty loss. Three class action lawsuits have been filed against the Company on behalf of occupants of the destroyed building and consolidated in the United States District Court for the District of New Jersey. The Company has agreed with class counsel to the terms of a proposed settlement which would provide a claims process (with agreed upon protocols for instructing the adjuster as to how to evaluate claims) and, if needed, an arbitration process to determine damage amounts to be paid to individual claimants covered by the class settlement. On July 8, 2016, class counsel filed with the court a motion for preliminary approval of this class settlement, and the Company did not oppose such motion. The Court administratively terminated this motion without prejudice due to the filing of an appeal of an order denying a motion to intervene in the settlement, but the Company expects that the motion will be re-filed shortly. The Company cannot predict when or if the court will approve the settlement. A fourth class action, being heard in the same federal court, was filed against the Company on behalf of residents of the second Edgewater building that suffered minimal damage. In addition to the class action lawsuits described above, 20 lawsuits representing approximately 141 individual plaintiffs have been filed in the Superior Court of New Jersey Bergen County - Law Division and 19 of these lawsuits are currently pending. All of these state court cases have been consolidated by the court; the Company believes that it has meritorious defenses to the extent of damages claimed in all of the suits. There are also three subrogation lawsuits that have been filed against the Company by insurers of Edgewater residents who obtained “renter’s insurance”; it is the Company’s position that in the majority of the applicable leases the residents waived subrogation rights. One of these lawsuits has been dismissed on that basis and the other two are currently pending in the United States District Court for the District of New Jersey. Having settled many third party claims through the insurance claims process, the Company currently believes that any potential remaining liability to third parties (including any potential liability to third parties determined in accordance with the class settlement described above, if approved) will not be material to the Company and will in any event be substantially covered by the Company's insurance policies. However, the Company can give no assurances in this regard and continues to evaluate this matter.
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	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 and disposition activity.
Recently Adopted Accounting Standards	Recently Issued Accounting Standards In May 2014, the FASB issued ASU 2014-09, Revenue from Contracts with Customers, a revenue recognition standard that will result in companies recognizing revenue from contracts when control for the service or product that is the subject of the contract is transferred from the seller to the buyer. In August 2015, the FASB issued ASU 2015-14, Revenue from Contracts with Customers-Deferral of the Effective Date, which defers the effective date of the new revenue recognition standard until the first quarter of 2018. Subsequently, the FASB has issued multiple ASU’s clarifying ASU 2014-09 and ASU 2015-14. The Company is assessing whether the new standard will have a material effect on its financial position or results of operations. In February 2016, the FASB issued ASU 2016-02, Leases, amending the existing accounting standards for lease accounting, including requiring lessees to recognize most leases on their balance sheets and making targeted changes to lessor accounting. The new standard requires a modified retrospective transition approach for all leases existing at, or entered into after, the date of initial application, with an option to use certain transition relief. The guidance will be effective in the first quarter of 2019 and allows for early adoption. The Company is assessing whether the new standard will have a material effect on its financial position or results of operations. In March 2016, the FASB issued ASU 2016-09, Compensation-Stock Compensation: Improvements to Employee Share-Based Payment Accounting, which simplifies several aspects of share-based payment transactions, including income tax consequences, classification of awards as equity or liability, statement of cash flows classification and policy election options for forfeitures. The new standard requires either a prospective, retrospective or modified retrospective approach depending on the amendment type. The guidance will be effective in the first quarter of 2017 and allows for early adoption. The Company is assessing whether the new standard will have a material effect on its financial position or results of operations. In August 2016, the FASB issued ASU 2016-15, Statement of Cash Flows (Topic 230): Classification of Certain Cash Receipts and Cash Payments. This ASU addresses eight specific cash flow issues including debt prepayment or debt extinguishment costs, proceeds from the settlement of insurance claims, distributions received from equity method investees and separately identifiable cash flows and application of the predominance principle. The new standard requires a retrospective approach. The guidance will be effective in the first quarter of 2018 and allows for early adoption. The Company is assessing whether the new standard will have a material effect on its financial position or results of operations.

Organization, Basis of Presen19

Organization, Basis of Presentation and Significant Accounting Policies (Tables)	9 Months Ended
	Sep. 30, 2016
Accounting Policies [Abstract]
Schedule of earnings per common share	The Company’s earnings per common share are determined as follows (dollars in thousands, except per share data): For the three months ended For the nine months ended 9/30/2016 9/30/2015 9/30/2016 9/30/2015 Basic and diluted shares outstanding Weighted average common shares - basic 136,997,756 133,669,584 136,901,164 132,516,847 Weighted average DownREIT units outstanding 7,500 7,500 7,500 7,500 Effect of dilutive securities 499,798 1,032,376 533,642 1,139,423 Weighted average common shares - diluted 137,505,054 134,709,460 137,442,306 133,663,770 Calculation of Earnings per Share - basic Net income attributable to common stockholders $ 356,392 $ 206,142 $ 791,767 $ 586,610 Net income allocated to unvested restricted shares (872 ) (467 ) (2,036 ) (1,444 ) Net income attributable to common stockholders, adjusted $ 355,520 $ 205,675 $ 789,731 $ 585,166 Weighted average common shares - basic 136,997,756 133,669,584 136,901,164 132,516,847 Earnings per common share - basic $ 2.60 $ 1.54 $ 5.77 $ 4.42 Calculation of Earnings per Share - diluted Net income attributable to common stockholders $ 356,392 $ 206,142 $ 791,767 $ 586,610 Add: noncontrolling interests of DownREIT unitholders in consolidated partnerships, including discontinued operations 10 9 30 28 Adjusted net income available to common stockholders $ 356,402 $ 206,151 $ 791,797 $ 586,638 Weighted average common shares - diluted 137,505,054 134,709,460 137,442,306 133,663,770 Earnings per common share - diluted $ 2.59 $ 1.53 $ 5.76 $ 4.39

Mortgage Notes Payable, Unsec20

Mortgage Notes Payable, Unsecured Notes and Credit Facility (Tables)	9 Months Ended
	Sep. 30, 2016
Debt Disclosure [Abstract]
Summary of company's mortgage notes payable, unsecured notes and Credit Facility excluding mortgage notes secured by communities classified as held for sale	The following amounts and discussion do not include the mortgage notes related to the communities classified as held for sale, if any, as of September 30, 2016 and December 31, 2015 , as shown in the accompanying Condensed Consolidated Balance Sheets (dollars in thousands) (see Note 6, “Real Estate Disposition Activities”). 9/30/2016 12/31/2015 Fixed rate unsecured notes (1) $ 3,800,000 $ 3,575,000 Term Loan 300,000 300,000 Fixed rate mortgage notes payable - conventional and tax-exempt (2) 1,672,758 1,561,109 Variable rate mortgage notes payable - conventional and tax-exempt (2) 908,621 1,045,182 Total mortgage notes payable and unsecured notes 6,681,379 6,481,291 Credit Facility 170,000 — Total mortgage notes payable, unsecured notes and Credit Facility $ 6,851,379 $ 6,481,291 _____________________________________ (1) Balances at September 30, 2016 and December 31, 2015 exclude $6,882 and $7,601 , respectively, of debt discount, and $22,871 and $21,725 , respectively, of deferred financing costs, as reflected in unsecured notes, net on the accompanying Condensed Consolidated Balance Sheets. (2) Balances at September 30, 2016 and December 31, 2015 exclude $6,501 and $19,686 , respectively, of debt premium, and $12,157 and $14,703 , respectively, of deferred financing costs, as reflected in mortgage notes payable on the accompanying Condensed Consolidated Balance Sheets.
Scheduled payments and maturities of mortgage notes payable and unsecured notes outstanding	Scheduled payments and maturities of mortgage notes payable and unsecured notes outstanding at September 30, 2016 are as follows (dollars in thousands): Year Secured notes payments Secured notes maturities Unsecured notes maturities Stated interest rate of unsecured notes 2016 $ 4,536 $ — $ — N/A 2017 18,671 709,591 250,000 5.700 % 2018 17,793 76,669 — N/A 2019 4,696 655,386 — N/A 2020 3,624 118,729 250,000 6.100 % 400,000 3.625 % 2021 3,551 27,844 250,000 3.950 % 300,000 LIBOR + 1.450% 2022 3,795 — 450,000 2.950 % 2023 4,040 — 350,000 4.200 % 250,000 2.850 % 2024 4,310 — 300,000 3.500 % 2025 4,585 84,835 525,000 3.450 % 300,000 3.500 % Thereafter 218,644 620,080 475,000 2.950 % $ 288,245 $ 2,293,134 $ 4,100,000

Equity (Tables)

Equity (Tables)	9 Months Ended
	Sep. 30, 2016
Stockholders' Equity Note [Abstract]
Summary of changes in equity	The following summarizes the changes in equity for the nine months ended September 30, 2016 (dollars in thousands): Common stock Additional paid-in capital Accumulated earnings less dividends Accumulated other comprehensive loss Total equity Balance at December 31, 2015 $ 1,370 $ 10,068,532 $ (197,989 ) $ (31,387 ) $ 9,840,526 Net income attributable to common stockholders — — 791,767 — 791,767 Loss on cash flow hedges — — — (73,826 ) (73,826 ) Cash flow hedge loss reclassified to earnings — — — 4,682 4,682 Change in redemption value of redeemable noncontrolling interest — — (529 ) — (529 ) Dividends declared to common stockholders — — (555,916 ) — (555,916 ) Issuance of common stock, net of withholdings 3 11,148 (1,290 ) — 9,861 Amortization of deferred compensation — 20,059 — — 20,059 Balance at September 30, 2016 $ 1,373 $ 10,099,739 $ 36,043 $ (100,531 ) $ 10,036,624

Investments in Real Estate En22

Investments in Real Estate Entities (Tables)	9 Months Ended
	Sep. 30, 2016
Equity Method Investments and Joint Ventures [Abstract]
Combined summary of the financial position of the entities accounted for using the equity method	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 (dollars in thousands): 9/30/2016 12/31/2015 (unaudited) (unaudited) Assets: Real estate, net $ 1,005,924 $ 1,392,833 Other assets 52,992 57,044 Total assets $ 1,058,916 $ 1,449,877 Liabilities and partners’ capital: Mortgage notes payable and credit facility $ 720,703 $ 947,205 Other liabilities 20,771 20,471 Partners’ capital 317,442 482,201 Total liabilities and partners’ capital $ 1,058,916 $ 1,449,877
Combined summary of the operating results of the entities accounted for using the equity method	The following is a combined summary of the operating results of the entities accounted for using the equity method discussed above for the periods presented (dollars in thousands): For the three months ended For the nine months ended 9/30/2016 9/30/2015 9/30/2016 9/30/2015 (unaudited) (unaudited) Rental and other income $ 30,771 $ 43,868 $ 101,534 $ 132,518 Operating and other expenses (12,069 ) (17,910 ) (39,206 ) (52,622 ) Gain on sale of communities — 66,410 180,256 98,899 Interest expense, net (1) (7,919 ) (14,883 ) (37,857 ) (35,694 ) Depreciation expense (8,081 ) (11,213 ) (26,027 ) (35,058 ) Net income $ 2,702 $ 66,272 $ 178,700 $ 108,043 _____________________________________ (1) Amount for the nine months ended September 30, 2016 includes charges for prepayment penalties and write-offs of deferred financing costs of $12,344 .

Segment Reporting (Tables)

Segment Reporting (Tables)	9 Months Ended
	Sep. 30, 2016
Segment Reporting [Abstract]
Schedule of reconciliation of NOI to net income	A reconciliation of NOI to net income for the three and nine months ended September 30, 2016 and 2015 is as follows (dollars in thousands): For the three months ended For the nine months ended 9/30/2016 9/30/2015 9/30/2016 9/30/2015 Net income $ 356,329 $ 206,076 $ 791,525 $ 586,381 Indirect operating expenses, net of corporate income 14,946 13,427 46,960 43,642 Investments and investment management expense 1,205 1,167 3,545 3,274 Expensed acquisition, development and other pursuit costs, net of recoveries 3,804 3,391 8,702 5,251 Interest expense, net 47,871 43,234 137,862 133,398 (Gain) loss on extinguishment of debt, net — (18,987 ) 2,461 (26,736 ) General and administrative expense 11,928 10,464 35,343 31,266 Equity in loss (income) of unconsolidated real estate entities 342 (20,554 ) (54,779 ) (68,925 ) Depreciation expense 131,729 120,184 391,414 355,664 Income tax expense 22 39 95 1,348 Casualty and impairment loss (gain), net — 658 (3,935 ) (10,668 ) Gain on sale of real estate (212,941 ) (35,216 ) (295,503 ) (115,798 ) Net operating income from real estate assets sold or held for sale (1) (5,525 ) (9,180 ) (19,751 ) (28,248 ) Net operating income $ 349,710 $ 314,703 $ 1,043,939 $ 909,849 __________________________________ (1) Represents NOI from real estate assets sold or held for sale as of September 30, 2016 that are not otherwise classified as discontinued operations.
Schedule of net operating income from real estate assets sold or held for sale, not classified as discontinued operations	The following is a summary of NOI from real estate assets sold or held for sale for the periods presented (dollars in thousands): For the three months ended For the nine months ended 9/30/2016 9/30/2015 9/30/2016 9/30/2015 Rental income from real estate assets sold or held for sale $ 8,814 $ 15,098 $ 31,731 $ 46,610 Operating expenses from real estate assets sold or held for sale (3,289 ) (5,918 ) (11,980 ) (18,362 ) Net operating income from real estate assets sold or held for sale $ 5,525 $ 9,180 $ 19,751 $ 28,248
Schedule of details of segment information	For the three months ended For the nine months ended Total NOI % NOI change from prior year Total NOI % NOI change from prior year Gross real estate (1) For the period ended September 30, 2016 Established New England $ 59,321 $ 37,657 0.6 % $ 174,731 $ 111,497 5.9 % $ 1,845,679 Metro NY/NJ 96,231 65,299 1.5 % 283,554 193,001 2.0 % 3,206,696 Mid-Atlantic 58,929 40,029 0.4 % 174,922 120,623 1.4 % 2,335,116 Pacific Northwest 20,216 14,502 9.5 % 59,333 42,753 6.6 % 736,377 Northern California 80,783 61,560 5.9 % 238,867 182,658 8.0 % 2,657,020 Southern California 73,570 52,527 11.1 % 217,686 155,242 10.3 % 2,667,875 Total Established 389,050 271,574 4.3 % 1,149,093 805,774 5.5 % 13,448,763 Other Stabilized (2) 53,905 34,812 N/A 177,016 125,017 N/A 2,325,539 Development / Redevelopment 63,122 43,324 N/A 164,865 113,148 N/A 3,994,361 Land Held for Future Development N/A N/A N/A N/A N/A N/A 519,626 Non-allocated (3) 1,320 N/A N/A 4,310 N/A N/A 74,374 Total $ 507,397 $ 349,710 11.1 % $ 1,495,284 $ 1,043,939 14.7 % $ 20,362,663 For the period ended September 30, 2015 Established New England $ 45,245 $ 29,036 3.4 % $ 132,054 $ 81,883 0.8 % $ 1,487,944 Metro NY/NJ 92,153 65,207 3.8 % 270,406 190,735 3.1 % 3,196,771 Mid-Atlantic 52,839 36,157 0.3 % 156,806 108,125 (0.4 )% 2,172,951 Pacific Northwest 17,319 12,077 5.0 % 50,563 36,214 8.0 % 720,223 Northern California 69,850 53,095 9.5 % 202,508 155,464 10.8 % 2,412,264 Southern California 65,019 43,714 7.9 % 190,513 130,278 9.1 % 2,505,625 Total Established 342,425 239,286 5.2 % 1,002,850 702,699 5.2 % 12,495,778 Other Stabilized 56,564 36,949 N/A 165,319 108,355 N/A 2,106,947 Development / Redevelopment 59,112 38,468 N/A 152,694 98,795 N/A 3,795,868 Land Held for Future Development N/A N/A N/A N/A N/A N/A 553,729 Non-allocated (3) 2,161 N/A N/A 7,714 N/A N/A 50,556 Total $ 460,262 $ 314,703 11.5 % $ 1,328,577 $ 909,849 12.8 % $ 19,002,878 __________________________________ (1) Does not include gross real estate assets held for sale of $135,054 as of September 30, 2016 . (2) Total revenue and NOI for the nine months ended September 30, 2016 includes $20,306 in business interruption insurance proceeds related to the Edgewater casualty loss. (3) Revenue represents third-party management, asset management and developer fees and miscellaneous income which are not allocated to a reportable segment.

Stock-Based Compensation Plans

Stock-Based Compensation Plans (Tables)	9 Months Ended
	Sep. 30, 2016
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Schedule of information with respect to stock options granted	Information with respect to stock options granted under the Company’s 1994 Stock Option and Incentive Plan (the “1994 Plan”) and its 2009 Stock Option and Incentive Plan (the “2009 Plan”) is as follows: 2009 Plan shares Weighted average exercise price per share 1994 Plan shares Weighted average exercise price per share Options Outstanding, December 31, 2015 249,178 $ 122.17 82,195 $ 103.27 Exercised (68,538 ) 116.37 (59,654 ) 112.85 Forfeited — — — — Options Outstanding, September 30, 2016 (1) 180,640 $ 124.37 22,541 $ 77.91
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, 2015 238,266 $ 119.65 Granted (1) 94,054 141.92 Change in units based on performance (2) 36,091 101.52 Converted to restricted stock (115,618 ) 94.67 Forfeited (1,630 ) 141.98 Outstanding at September 30, 2016 251,163 $ 136.74 __________________________________ (1) The amount of restricted stock that ultimately may be earned is based on the total shareholder return metrics related to the Company’s common stock for 61,039 performance awards and financial metrics related to operating performance and leverage metrics of the Company for 33,015 performance awards. (2) Represents the change in the number of performance awards earned based on performance achievement.
Summary of valuation options	The Company used a Monte Carlo model to assess the compensation cost associated with the portion of the performance awards determined by using total shareholder return measures. The assumptions used are as follows: 2016 Dividend yield 3.3% Estimated volatility over the life of the plan (1) 15.2% - 22.8% Risk free rate 0.44% - 0.88% Estimated performance award value based on total shareholder return measure $131.24 __________________________________ (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, 2015 147,884 $ 146.21 98,347 Granted - restricted stock shares 80,873 162.34 115,618 Vested - restricted stock shares (84,623 ) 141.49 (36,872 ) Forfeited (3,453 ) 162.34 (395 ) Outstanding at September 30, 2016 140,681 $ 157.49 176,698

Fair Value (Tables)

Fair Value (Tables)	9 Months Ended
	Sep. 30, 2016
Fair Value Disclosures [Abstract]
Schedule of summary of consolidated Hedging Derivatives, excluding derivatives executed to hedge debt on communities classified as held for sale	The following table summarizes the consolidated derivative positions at September 30, 2016 (dollars in thousands): Non-designated Hedges Interest Rate Caps Cash Flow Hedges Interest Rate Caps Cash Flow Hedges Interest Rate Swaps Notional balance $ 722,943 $ 36,108 $ 800,000 Weighted average interest rate (1) 2.6 % 2.7 % N/A Weighted average swapped/capped interest rate 6.2 % 5.9 % 2.3 % Earliest maturity date Nov 2016 Apr 2019 Nov 2017 Latest maturity date Jul 2021 Apr 2019 Nov 2017 ____________________________________ (1) For interest rate caps, represents the weighted average interest rate on the hedged debt.
Schedule of Cash Flow Hedges Included in Accumulated Other Comprehensive Income (Loss) [Table Text Block]	For the three months ended For the nine months ended 9/30/2016 9/30/2015 9/30/2016 9/30/2015 Cash flow hedge losses reclassified to earnings $ 1,748 $ 1,373 $ 4,682 $ 4,401
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): Description Total Fair Value Quoted Prices (Level 1) Significant (Level 2) Significant (Level 3) 9/30/2016 Non-Designated Hedges Interest Rate Caps $ 16 $ — $ 16 $ — Cash Flow Hedges Interest Rate Caps — — — — Interest Rate Swaps (53,591 ) — (53,591 ) — Puts (8,181 ) — — (8,181 ) DownREIT units (1,334 ) (1,334 ) — — Indebtedness Unsecured notes (3,988,324 ) (3,988,324 ) — — Mortgage notes payable, Credit Facility and Term Loan (2,985,133 ) — (2,985,133 ) — Total $ (7,036,547 ) $ (3,989,658 ) $ (3,038,708 ) $ (8,181 ) Description Total Fair Value Quoted Prices (Level 1) Significant (Level 2) Significant (Level 3) 12/31/2015 Non-Designated Hedges Interest Rate Caps $ 26 $ — $ 26 $ — Cash Flow Hedges Interest Rate Caps 5 — 5 — Interest Rate Swaps 5,422 — 5,422 — Puts (8,181 ) — — (8,181 ) DownREIT units (1,381 ) (1,381 ) — — Indebtedness Unsecured notes (3,668,417 ) (3,668,417 ) — — Mortgage notes payable, Credit Facility and Term Loan (2,700,341 ) — (2,700,341 ) — Total $ (6,372,867 ) $ (3,669,798 ) $ (2,694,888 ) $ (8,181 )

Organization, Basis of Presen26

Organization, Basis of Presentation and Significant Accounting Policies (Details)	Sep. 30, 2016statecommunityhome
Organization and Basis of Presentation
Number of operating apartment communities | community	261
Number of apartment homes included in operating apartment communities owned | home	75,254
Number of states where operating apartment communities owned are located | state	10
Number of communities with apartments under reconstruction | community	8
Number of apartment homes under reconstruction | home	3,363
Number of owned communities under construction | community	22
Expected number of apartment homes under construction | home	7,454
Communities under development rights | community	28
Estimated number of apartment homes in communities to be developed | home	9,550

Organization, Basis of Presen27

Organization, Basis of Presentation and Significant Accounting Policies (Details 2) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016USD ($)communityClaimhomebuilding$ / sharesshares	Sep. 30, 2015USD ($)$ / sharesshares	Sep. 30, 2016USD ($)communityClaimhomeplaintiffbuilding$ / sharesshares	Sep. 30, 2015USD ($)$ / sharesshares
Basic and diluted shares outstanding
Weighted average common shares - basic (in shares) | shares	136,997,756	133,669,584	136,901,164	132,516,847
Weighted average DownREIT units outstanding (in shares) | shares	7,500	7,500	7,500	7,500
Effect of dilutive securities (in shares) | shares	499,798	1,032,376	533,642	1,139,423
Weighted average common shares - diluted (in shares) | shares	137,505,054	134,709,460	137,442,306	133,663,770
Calculation of Earnings per Share - basic
Net income attributable to common stockholders | $	$ 356,392	$ 206,142	$ 791,767	$ 586,610
Net income allocated to unvested restricted shares | $	(872)	(467)	(2,036)	(1,444)
Net income attributable to common stockholders, adjusted | $	$ 355,520	$ 205,675	$ 789,731	$ 585,166
Weighted average common shares - basic (in shares) | shares	136,997,756	133,669,584	136,901,164	132,516,847
Earnings per common share - basic (in dollars per share) | $ / shares	$ 2.60	$ 1.54	$ 5.77	$ 4.42
Calculation of Earnings per Share - diluted
Net income attributable to common stockholders | $	$ 356,392	$ 206,142	$ 791,767	$ 586,610
Add: noncontrolling interests of DownREIT unitholders in consolidated partnerships, including discontinued operations | $	10	9	30	28
Adjusted net income available to common stockholders | $	$ 356,402	$ 206,151	$ 791,797	$ 586,638
Weighted average common shares - diluted (in shares) | shares	137,505,054	134,709,460	137,442,306	133,663,770
Earnings per common share - diluted (in dollars per share) | $ / shares	$ 2.59	$ 1.53	$ 5.76	$ 4.39
Estimated forfeiture rate of stock options (as a percent)			0.80%
Loss Contingencies [Line Items]
Number of Real Estate Properties | community	261		261
Number of apartment homes included in operating apartment communities owned | home	75,254		75,254
Avalon at Edgewater [Member]
Loss Contingencies [Line Items]
Number of Real Estate Properties | building	2		2
Number Of Real Estate Properties, Uninhabitable | building	1		1
Number Of Units In Real Estate Property, Uninhabitable | home	240		240
Number of apartment homes included in operating apartment communities owned | home	168		168
Loss Contingency New Class Action Claims Filed Number			3
Loss Contingency Total Class Action Claims Filed Number			4
Loss Contingency, New Claims Filed, Number			20
Loss Contingency, Number of Plaintiffs | plaintiff			141
Loss Contingency, Pending Claims, Number	19		19
Loss Contingency New Subrogation Claims Filed Number			3
Loss Contingency Subrogation Claims Filed Dismissed Number			1
Loss Contingency Subrogation Claims Filed Pending Number			2

Interest Capitalized (Details)

Interest Capitalized (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Interest Capitalized
Capitalized interest during the development and redevelopment of real estate assets	$ 19,889	$ 20,356	$ 60,522	$ 59,186

Mortgage Notes Payable, Unsec29

Mortgage Notes Payable, Unsecured Notes and Credit Facility (Details) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Notes Payable, Unsecured Notes and Credit Facility
Total notes payable and unsecured notes	$ 6,681,379	$ 6,481,291
Credit Facility	170,000	0
Total mortgage notes payable, unsecured notes and Credit Facility	6,851,379	6,481,291
Unsecured notes
Notes Payable, Unsecured Notes and Credit Facility
Fixed rate notes	3,800,000	3,575,000
Total notes payable and unsecured notes	4,100,000
Amount of debt discount	6,882	7,601
Deferred Finance Costs, Net	22,871	21,725
Term Loan
Notes Payable, Unsecured Notes and Credit Facility
Variable rate notes	300,000	300,000
Secured notes
Notes Payable, Unsecured Notes and Credit Facility
Fixed rate notes	1,672,758	1,561,109
Variable rate notes	908,621	1,045,182
Total notes payable and unsecured notes	2,293,134
Deferred Finance Costs, Net	12,157	14,703
Amount of debt premium	$ 6,501	$ 19,686

Mortgage Notes Payable, Unsec30

Mortgage Notes Payable, Unsecured Notes and Credit Facility (Details 2) - USD ($)	1 Months Ended				3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2016	May 31, 2016	Apr. 30, 2016	Feb. 29, 2016	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015	Jan. 31, 2016
Notes Payable, Unsecured Notes and Credit Facility
Current interest rate (as a percent)		3.35%
(Gain) loss on extinguishment of debt, net					$ 0	$ (18,987,000)	$ 2,461,000	$ (26,736,000)
Debt Instrument, Interest Rate, Stated Percentage		2.95%
Repayments of Unsecured Debt							250,000,000	$ 0
Variable rate unsecured credit facility	$ 170,000,000				170,000,000		170,000,000		$ 0
Net carrying value of apartment communities and improved land parcels securing debt	3,482,680,000				$ 3,482,680,000		$ 3,482,680,000
Unsecured notes
Notes Payable, Unsecured Notes and Credit Facility
Repayments of Unsecured Debt	$ 250,000,000
Long-term Debt, Percentage Bearing Fixed Interest, Percentage Rate	5.75%				5.75%		5.75%
Mortgage notes payable
Notes Payable, Unsecured Notes and Credit Facility
Mortgage notes payable held by wholly owned subsidiaries guaranteed by the Company	$ 100,000,000				$ 100,000,000		$ 100,000,000
Unsecured Notes 2.95 Percent [Member]
Notes Payable, Unsecured Notes and Credit Facility
Debt Instrument, Face Amount		$ 475,000,000
Proceeds from Issuance of Debt		$ 471,751,000
Notes Payable Maturities 2020 [Member] | Avalon Hoboken [Member] | Mortgage notes payable
Notes Payable, Unsecured Notes and Credit Facility
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Noncurrent Liabilities, Long-term Debt										$ 67,904,000
Current interest rate (as a percent)										4.18%
Notes Payable Maturities 2016 [Member] | Mortgage notes payable
Notes Payable, Unsecured Notes and Credit Facility
Current interest rate (as a percent)				3.32%
Repayments of secured mortgages				$ 16,212,000
Notes Payable Maturities 2046 [Member]
Notes Payable, Unsecured Notes and Credit Facility
(Gain) loss on extinguishment of debt, net			$ (2,461,000)
Notes Payable Maturities 2046 [Member] | Mortgage notes payable
Notes Payable, Unsecured Notes and Credit Facility
Repayments of secured mortgages			$ 134,500,000
Notes Payable Maturities 2019 [Member] | Avalon Columbia Pike [Member] | Mortgage notes payable
Notes Payable, Unsecured Notes and Credit Facility
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Noncurrent Liabilities, Long-term Debt	$ 70,507,000				$ 70,507,000		$ 70,507,000
Current interest rate (as a percent)	3.38%				3.38%		3.38%
Variable rate unsecured credit facility
Notes Payable, Unsecured Notes and Credit Facility
Available borrowing capacity	$ 1,500,000,000				$ 1,500,000,000		$ 1,500,000,000		$ 1,300,000,000
Line of credit facility, extension period							9 months
Extension fee							$ 1,500,000
Period of borrowing rate assumed							1 month
Percent of Credit Facility Available to Competitive Bid Option	65.00%				65.00%		65.00%
Line of Credit Facility, Commitment Fee Percentage							0.125%		0.15%
Annual facility fee							$ 1,875,000
Variable rate unsecured credit facility									$ 0
Outstanding balance of letters of credit	$ 53,137,000				$ 53,137,000		$ 53,137,000		$ 43,049,000
Variable rate unsecured credit facility | LIBOR
Notes Payable, Unsecured Notes and Credit Facility
Current interest rate (as a percent)	1.36%				1.36%		1.36%
Debt instrument, basis spread on variable rate (as a percent)							0.825%
Variable rate unsecured credit facility | Minimum [Member]
Notes Payable, Unsecured Notes and Credit Facility
Debt instrument, basis spread on variable rate (as a percent)							0.80%
Variable rate unsecured credit facility | Maximum [Member]
Notes Payable, Unsecured Notes and Credit Facility
Debt instrument, basis spread on variable rate (as a percent)							1.55%
Secured Mortgage | LIBOR
Notes Payable, Unsecured Notes and Credit Facility
Debt instrument variable rate							LIBOR
Fixed rate mortgage notes payable
Notes Payable, Unsecured Notes and Credit Facility
Weighted average interest rate, debt (as a percent)	4.40%				4.40%		4.40%		4.60%
Variable rate mortgage notes payable, unsecured term loan and Credit Facility
Notes Payable, Unsecured Notes and Credit Facility
Weighted average interest rate, debt (as a percent)	2.30%				2.30%		2.30%		1.80%

Mortgage Notes Payable, Unsec31

Mortgage Notes Payable, Unsecured Notes and Credit Facility (Details 3) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2016	May 31, 2016	Dec. 31, 2015
Notes Payable, Unsecured Notes and Credit Facility
Mortgage notes payable and unsecured notes	$ 6,681,379		$ 6,481,291
Stated interest rate of unsecured notes (as a percent)		2.95%
Secured notes
Notes Payable, Unsecured Notes and Credit Facility
Secured notes payments	288,245
Mortgage notes payable and unsecured notes	2,293,134
Secured notes | Notes Payable Maturities 2016 [Member]
Notes Payable, Unsecured Notes and Credit Facility
Secured notes payments	4,536
Mortgage notes payable and unsecured notes	0
Secured notes | Notes Payable Maturities 2017 [Member]
Notes Payable, Unsecured Notes and Credit Facility
Secured notes payments	18,671
Mortgage notes payable and unsecured notes	709,591
Secured notes | Notes Payable Maturities 2018 [Member]
Notes Payable, Unsecured Notes and Credit Facility
Secured notes payments	17,793
Mortgage notes payable and unsecured notes	76,669
Secured notes | Notes Payable Maturities 2019 [Member]
Notes Payable, Unsecured Notes and Credit Facility
Secured notes payments	4,696
Mortgage notes payable and unsecured notes	655,386
Secured notes | Notes Payable Maturities 2020 [Member]
Notes Payable, Unsecured Notes and Credit Facility
Secured notes payments	3,624
Mortgage notes payable and unsecured notes	118,729
Secured notes | Notes payable maturing in 2021
Notes Payable, Unsecured Notes and Credit Facility
Secured notes payments	3,551
Mortgage notes payable and unsecured notes	27,844
Secured notes | Notes payable maturing in 2022
Notes Payable, Unsecured Notes and Credit Facility
Secured notes payments	3,795
Secured notes | Notes payable maturing in 2023
Notes Payable, Unsecured Notes and Credit Facility
Secured notes payments	4,040
Secured notes | Notes Payable Maturities 2024 [Member]
Notes Payable, Unsecured Notes and Credit Facility
Secured notes payments	4,310
Secured notes | Notes Payable 3.450 Maturities 2025 [Member]
Notes Payable, Unsecured Notes and Credit Facility
Secured notes payments	4,585
Mortgage notes payable and unsecured notes	84,835
Secured notes | Notes payable with maturities after 2023
Notes Payable, Unsecured Notes and Credit Facility
Secured notes payments	218,644
Mortgage notes payable and unsecured notes	620,080
Unsecured notes
Notes Payable, Unsecured Notes and Credit Facility
Mortgage notes payable and unsecured notes	4,100,000
Unsecured notes | Notes Payable Maturities 2016 [Member]
Notes Payable, Unsecured Notes and Credit Facility
Mortgage notes payable and unsecured notes	0
Unsecured notes | Notes Payable Maturities 2017 [Member]
Notes Payable, Unsecured Notes and Credit Facility
Mortgage notes payable and unsecured notes	$ 250,000
Stated interest rate of unsecured notes (as a percent)	5.70%
Unsecured notes | Notes Payable 6.100 Percent Maturities 2020
Notes Payable, Unsecured Notes and Credit Facility
Mortgage notes payable and unsecured notes	$ 250,000
Stated interest rate of unsecured notes (as a percent)	6.10%
Unsecured notes | Notes Payable 3.625 Percent Maturities 2020
Notes Payable, Unsecured Notes and Credit Facility
Mortgage notes payable and unsecured notes	$ 400,000
Stated interest rate of unsecured notes (as a percent)	3.625%
Unsecured notes | Notes payable maturing in 2021
Notes Payable, Unsecured Notes and Credit Facility
Mortgage notes payable and unsecured notes	$ 250,000
Stated interest rate of unsecured notes (as a percent)	3.95%
Unsecured notes | Term Loan
Notes Payable, Unsecured Notes and Credit Facility
Mortgage notes payable and unsecured notes	$ 300,000
Unsecured notes | Term Loan | LIBOR
Notes Payable, Unsecured Notes and Credit Facility
Debt instrument variable rate	LIBOR
Debt instrument, basis spread on variable rate (as a percent)	1.45%
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 | Notes payable maturing in 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 [Member]
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 3.450 Maturities 2025 [Member]
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 [Member]
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 with maturities after 2023
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%

Equity (Details)

Equity (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Changes in equity
Beginning Balance			$ 9,840,526
Net income attributable to common stockholders	$ 356,392	$ 206,142	791,767	$ 586,610
Income (loss) on cash flow hedges	719	(31)	(73,826)	(67)
Cash flow hedge loss reclassified to earnings	1,748	$ 1,373	4,682	4,401
Change in redemption value of redeemable noncontrolling interest			(529)
Dividends declared to common stockholders			(555,916)
Issuance of common stock, net of withholdings			9,861
Amortization of deferred compensation			20,059
Ending Balance	10,036,624		10,036,624
Common stock
Changes in equity
Beginning Balance			1,370
Issuance of common stock, net of withholdings			3
Ending Balance	1,373		1,373
Additional paid-in capital
Changes in equity
Beginning Balance			10,068,532
Issuance of common stock, net of withholdings			11,148
Amortization of deferred compensation			20,059
Ending Balance	10,099,739		10,099,739
Accumulated earnings less dividends
Changes in equity
Beginning Balance			(197,989)
Net income attributable to common stockholders			791,767
Change in redemption value of redeemable noncontrolling interest			(529)	$ 1,722
Dividends declared to common stockholders			(555,916)
Issuance of common stock, net of withholdings			(1,290)
Ending Balance	36,043		36,043
Accumulated other comprehensive loss
Changes in equity
Beginning Balance			(31,387)
Income (loss) on cash flow hedges			(73,826)
Cash flow hedge loss reclassified to earnings			4,682
Ending Balance	$ (100,531)		$ (100,531)

Equity (Details 2)

Equity (Details 2) - USD ($)	3 Months Ended	9 Months Ended
	Sep. 30, 2016	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015
Class of Stock [Line Items]
Common stock, shares authorized (in shares)	280,000,000	280,000,000		280,000,000
Preferred stock, shares authorized (in shares)	50,000,000	50,000,000		50,000,000
Common stock shares issued in connection with stock options exercised (in shares)		128,192
Common stock issued through the dividend reinvestment plan (in shares)		1,689	1,608
Number of shares of stock grants withheld (in shares)		53,214	39,800
Stock Issued During Period, Shares, Employee Stock Purchase Plans (in shares)		5,671
Stock Issued During Period, Shares, Share-based Compensation, Forfeited (in shares)		407	4,293
Continuous Equity Program CEP IV [Member]
Class of Stock [Line Items]
Maximum value of shares of common stock that can be sold (in dollars)	$ 1,000,000,000	$ 1,000,000,000
Common stock shares issued	0	0
Maximum [Member] | Continuous Equity Program CEP IV [Member]
Class of Stock [Line Items]
Percentage of compensation received by sales agent		2.00%
Restricted Stock and Restricted Stock Converted From Performance Shares [Member]
Class of Stock [Line Items]
Restricted stock granted (in shares)		196,491	157,779
Deferred Compensation, Share-based Payments [Member] | Non Employee Director [Member]
Class of Stock [Line Items]
Restricted stock granted (in shares)		44,327	46,589

Investments in Real Estate En34

Investments in Real Estate Entities (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016USD ($)entity	Sep. 30, 2015USD ($)	Sep. 30, 2016USD ($)communityentityhome	Sep. 30, 2015USD ($)	Dec. 31, 2015USD ($)
Investment in Real Estate Entities
Number of Apartment Communities Sold | community			5
Gain on sale of communities	$ 0	$ 66,410	$ 180,256	$ 98,899
Gains (Losses) on Extinguishment of Debt	0	18,987	(2,461)	26,736
Equity Method Investment, Difference Between Carrying Amount and Underlying Equity	38,485		38,485		$ 40,978
Other than Temporary Impairment Losses, Investments	$ 0	$ 0	$ 0	$ 0
Unconsolidated real estate entities
Investment in Real Estate Entities
Number of unconsolidated real estate entities | entity	5		5
Unconsolidated real estate entities | Minimum
Investment in Real Estate Entities
Equity Method Investment, Ownership Percentage	20.00%		20.00%
Unconsolidated real estate entities | Maximum
Investment in Real Estate Entities
Equity Method Investment, Ownership Percentage	31.30%		31.30%
Avalon Bay Value Added Fund II LP [Member]
Investment in Real Estate Entities
Equity Method Investment, Ownership Percentage	31.30%		31.30%
Number of Apartment Communities Sold | community			2
Repayments of secured mortgages			$ 127,191
Gains (Losses) on Extinguishment of Debt			$ 1,670
Percentage of Right of Distribution	20.00%		20.00%
Percentage of Right of Remaining Distribution	80.00%		80.00%
Proceeds from Equity Method Investment, Dividends or Distributions	$ 3,447
Avalon Bay Value Added Fund II LP [Member] | Eaves Rancho San Diego [Member]
Investment in Real Estate Entities
Number of apartment homes sold | home			676
Proceeds from sale of real estate			$ 158,000
Gain on sale of communities			$ 13,057
Avalon Bay Value Added Fund II LP [Member] | Eaves Tustin [Member]
Investment in Real Estate Entities
Number of apartment homes sold | home			628
Proceeds from sale of real estate			$ 163,550
Gain on sale of communities			$ 23,547
US Fund [Member]
Investment in Real Estate Entities
Number of Apartment Communities Sold | community			2
Repayments of secured mortgages			$ 94,822
Gains (Losses) on Extinguishment of Debt			$ 2,003
US Fund [Member] | Archstone Boca Town Center [Member]
Investment in Real Estate Entities
Number of apartment homes sold | home			252
Proceeds from sale of real estate			$ 56,300
Gain on sale of communities			$ 4,120
US Fund [Member] | Avalon Kips Bay [Member]
Investment in Real Estate Entities
Number of apartment homes sold | home			209
Proceeds from sale of real estate			$ 173,000
Gain on sale of communities			12,448
Funds [Member]
Investment in Real Estate Entities
Gains (Losses) on Extinguishment of Debt			$ 12,344

Investments in Real Estate En35

Investments in Real Estate Entities (Details 2) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015
Assets:
Real estate, net	$ 1,005,924		$ 1,005,924		$ 1,392,833
Other assets	52,992		52,992		57,044
Total assets	1,058,916		1,058,916		1,449,877
Liabilities and partners' capital:
Mortgage notes payable and credit facility	720,703		720,703		947,205
Other liabilities	20,771		20,771		20,471
Partners' capital	317,442		317,442		482,201
Total liabilities and partners' capital	1,058,916		1,058,916		$ 1,449,877
Combined summary of the operating results of the accounted for using the equity method
Rental and other income	30,771	$ 43,868	101,534	$ 132,518
Operating and other expenses	(12,069)	(17,910)	(39,206)	(52,622)
Gain on sale of communities	0	66,410	180,256	98,899
Interest expense, net	(7,919)	(14,883)	(37,857)	(35,694)
Depreciation expense	(8,081)	(11,213)	(26,027)	(35,058)
Net income	$ 2,702	$ 66,272	$ 178,700	$ 108,043

Investments in Real Estate En36

Investments in Real Estate Entities (Details 3) $ in Thousands	3 Months Ended		9 Months Ended		15 Months Ended
	Sep. 30, 2016USD ($)	Sep. 30, 2015USD ($)	Sep. 30, 2016USD ($)communityland_parcelhome	Sep. 30, 2015USD ($)	Mar. 31, 2016USD ($)	May 31, 2016	Jan. 31, 2016USD ($)	Dec. 31, 2015USD ($)
Business Acquisition [Line Items]
Investments in unconsolidated real estate entities	$ 176,882		$ 176,882					$ 216,919
Gain on sale of other real estate	10,778	$ 0	$ 10,921	$ 9,647
Number of Communities Acquired | community			4
Current interest rate (as a percent)						3.35%
Business Combination, Acquisition Related Costs, Abandoned Pursuit Costs	3,804	3,391	$ 7,086	5,251
Real Estate [Line Items]
Impairment of Real Estate	0	658	$ (3,935)	(10,668)
Number of Land Parcels Impaired | land_parcel			3
Real Estate Investment Property, Net	14,812,162		$ 14,812,162					$ 13,847,526
Avalon Hoboken [Member]
Business Acquisition [Line Items]
Number of Apartment Homes, Acquired | home			217
Business Combination, Consideration Transferred			$ 129,700
Avalon Potomac Yard [Member]
Business Acquisition [Line Items]
Number of Apartment Homes, Acquired | home			323
Business Combination, Consideration Transferred			$ 108,250
Avalon Columbia Pike [Member]
Business Acquisition [Line Items]
Number of Apartment Homes, Acquired | home			269
Business Combination, Consideration Transferred			$ 102,000
Studio 77 [Member]
Business Acquisition [Line Items]
Number of Apartment Homes, Acquired | home			156
Business Combination, Consideration Transferred			$ 72,100
Notes Payable Maturities 2020 [Member] | Secured notes | Avalon Hoboken [Member]
Business Acquisition [Line Items]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Noncurrent Liabilities, Long-term Debt							$ 67,904
Current interest rate (as a percent)							4.18%
Notes Payable Maturities 2019 [Member] | Secured notes | Avalon Columbia Pike [Member]
Business Acquisition [Line Items]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Noncurrent Liabilities, Long-term Debt	$ 70,507		$ 70,507
Current interest rate (as a percent)	3.38%		3.38%
Land [Member]
Real Estate [Line Items]
Impairment of Real Estate		0	$ 10,500	0
Avalon at Edgewater [Member]
Real Estate [Line Items]
Impairment of Real Estate			(8,702)	(15,663)
Insurance Proceeds			29,008	44,142	$ 73,150
Real Estate Investment Property, Net		21,844		21,844
Casualty Loss		$ 658		6,635
Gain on Business Interruption Insurance Recovery			20,306
New England [Member]
Real Estate [Line Items]
Impairment of Real Estate			(5,732)
Insurance Proceeds			8,493
Casualty Loss			$ 2,761
AVA North Point [Member]
Business Acquisition [Line Items]
Equity Method Investment, Ownership Percentage	55.00%		55.00%
Gain on sale of other real estate			$ 10,621
Avalon Clarendon [Member]
Business Acquisition [Line Items]
Equity Method Investments	$ 120,300		$ 120,300
Number of Apartment Homes, Acquired | home			300
Gains (Losses) on Sales of Investment Real Estate			$ 4,322
Investments in unconsolidated real estate entities	$ 115,848		$ 115,848
New England [Member]
Real Estate [Line Items]
Impairment of Real Estate				4,195
New England [Member] | Avalon at Edgewater [Member]
Real Estate [Line Items]
Impairment of Real Estate				$ 26,039
Joint Venture Partner [Member] | AVA North Point [Member]
Business Acquisition [Line Items]
Equity Method Investment, Ownership Percentage	45.00%		45.00%

Real Estate Disposition Activ37

Real Estate Disposition Activities (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016USD ($)communityland_parcel	Sep. 30, 2015USD ($)	Sep. 30, 2016USD ($)communityland_parcelhome	Sep. 30, 2015USD ($)
Summary of income from discontinued operations
Number of Apartment Communities Sold | community			5
Gain on sale of communities	$ 202,163	$ 35,216	$ 284,582	$ 106,151
Number of Communities Held for Sale | community	3		3
Number of Land Parcels Held For Sale | land_parcel	3		3
Eaves Trumbull [Member]
Summary of income from discontinued operations
Apartment homes | home			340
Proceeds from Sale of Real Estate			$ 70,250
Gain on sale of communities			$ 51,430
Avalon Essex [Member]
Summary of income from discontinued operations
Apartment homes | home			154
Proceeds from Sale of Real Estate			$ 45,100
Gain on sale of communities			$ 31,081
Eaves Nanuet [Member]
Summary of income from discontinued operations
Apartment homes | home			504
Proceeds from Sale of Real Estate			$ 147,000
Gain on sale of communities			$ 118,008
Avalon Shrewsbury [Member]
Summary of income from discontinued operations
Apartment homes | home			251
Proceeds from Sale of Real Estate			$ 60,500
Gain on sale of communities			$ 33,350
Avalon at Freehold [Member]
Summary of income from discontinued operations
Apartment homes | home			296
Proceeds from Sale of Real Estate			$ 68,000
Gain on sale of communities			$ 46,482

Segment Reporting (Details)

Segment Reporting (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Reconciliation of NOI to net income
Net income	$ 356,329	$ 206,076	$ 791,525	$ 586,381
Indirect operating expenses, net of corporate income	14,946	13,427	46,960	43,642
Investments and investment management expense	1,205	1,167	3,545	3,274
Expensed acquisition, development and other pursuit costs, net of recoveries	3,804	3,391	8,702	5,251
Interest expense, net	47,871	43,234	137,862	133,398
(Gain) loss on extinguishment of debt, net	0	(18,987)	2,461	(26,736)
General and administrative expense	11,928	10,464	35,343	31,266
Equity in (income) loss of unconsolidated real estate entities	342	(20,554)	(54,779)	(68,925)
Depreciation expense	131,729	120,184	391,414	355,664
Income tax expense	22	39	95	1,348
Casualty and Impairment Loss (Gain)	0	658	(3,935)	(10,668)
Gain on sale of real estate assets in continuing operations	(212,941)	(35,216)	(295,503)	(115,798)
Net operating income from real estate assets sold or held for sale (1)	(5,525)	(9,180)	(19,751)	(28,248)
Net operating income	$ 349,710	$ 314,703	$ 1,043,939	$ 909,849

Segment Reporting (Details 2)

Segment Reporting (Details 2) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Segment Reporting [Abstract]
Rental income from real estate assets sold or held for sale	$ 8,814	$ 15,098	$ 31,731	$ 46,610
Operating expenses from real estate assets sold or held for sale	(3,289)	(5,918)	(11,980)	(18,362)
Income (Loss) From Assets Held for Sale, Not Classified as Discontinued Operations	$ 5,525	$ 9,180	$ 19,751	$ 28,248

Segment Reporting (Details 3)

Segment Reporting (Details 3) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Segment Reporting
Total revenue	$ 516,211	$ 475,360	$ 1,527,015	$ 1,375,187
NOI	$ 349,710	$ 314,703	$ 1,043,939	$ 909,849
% NOI change from prior year	11.10%	11.50%	14.70%	12.80%
Gross real estate	$ 20,362,663	$ 19,002,878	$ 20,362,663	$ 19,002,878
Gross real estate assets held for sale	135,054		135,054
Avalon at Edgewater [Member]
Segment Reporting
Gain on Business Interruption Insurance Recovery			20,306
Operating Segments | Established
Segment Reporting
Total revenue	389,050	342,425	1,149,093	1,002,850
NOI	$ 271,574	$ 239,286	$ 805,774	$ 702,699
% NOI change from prior year	4.30%	5.20%	5.50%	5.20%
Gross real estate	$ 13,448,763	$ 12,495,778	$ 13,448,763	$ 12,495,778
Operating Segments | Established | New England [Member]
Segment Reporting
Total revenue	59,321	45,245	174,731	132,054
NOI	$ 37,657	$ 29,036	$ 111,497	$ 81,883
% NOI change from prior year	0.60%	3.40%	5.90%	0.80%
Gross real estate	$ 1,845,679	$ 1,487,944	$ 1,845,679	$ 1,487,944
Operating Segments | Established | Metro NY/NJ
Segment Reporting
Total revenue	96,231	92,153	283,554	270,406
NOI	$ 65,299	$ 65,207	$ 193,001	$ 190,735
% NOI change from prior year	1.50%	3.80%	2.00%	3.10%
Gross real estate	$ 3,206,696	$ 3,196,771	$ 3,206,696	$ 3,196,771
Operating Segments | Established | Mid-Atlantic
Segment Reporting
Total revenue	58,929	52,839	174,922	156,806
NOI	$ 40,029	$ 36,157	$ 120,623	$ 108,125
% NOI change from prior year	0.40%	0.30%	1.40%	(0.40%)
Gross real estate	$ 2,335,116	$ 2,172,951	$ 2,335,116	$ 2,172,951
Operating Segments | Established | Pacific Northwest
Segment Reporting
Total revenue	20,216	17,319	59,333	50,563
NOI	$ 14,502	$ 12,077	$ 42,753	$ 36,214
% NOI change from prior year	9.50%	5.00%	6.60%	8.00%
Gross real estate	$ 736,377	$ 720,223	$ 736,377	$ 720,223
Operating Segments | Established | Northern California
Segment Reporting
Total revenue	80,783	69,850	238,867	202,508
NOI	$ 61,560	$ 53,095	$ 182,658	$ 155,464
% NOI change from prior year	5.90%	9.50%	8.00%	10.80%
Gross real estate	$ 2,657,020	$ 2,412,264	$ 2,657,020	$ 2,412,264
Operating Segments | Established | Southern California
Segment Reporting
Total revenue	73,570	65,019	217,686	190,513
NOI	$ 52,527	$ 43,714	$ 155,242	$ 130,278
% NOI change from prior year	11.10%	7.90%	10.30%	9.10%
Gross real estate	$ 2,667,875	$ 2,505,625	$ 2,667,875	$ 2,505,625
Operating Segments | Other Stabilized
Segment Reporting
Total revenue	53,905	56,564	177,016	165,319
NOI	34,812	36,949	125,017	108,355
Gross real estate	2,325,539	2,106,947	2,325,539	2,106,947
Operating Segments | Development / Redevelopment
Segment Reporting
Total revenue	63,122	59,112	164,865	152,694
NOI	43,324	38,468	113,148	98,795
Gross real estate	3,994,361	3,795,868	3,994,361	3,795,868
Land Held for Future Development
Segment Reporting
Gross real estate	519,626	553,729	519,626	553,729
Non-allocated
Segment Reporting
Total revenue	1,320	2,161	4,310	7,714
Gross real estate	74,374	50,556	74,374	50,556
Continuing Operations
Segment Reporting
Total revenue	$ 507,397	$ 460,262	$ 1,495,284	$ 1,328,577

Stock-Based Compensation Plan41

Stock-Based Compensation Plans (Details)	9 Months Ended
	Sep. 30, 2016$ / sharesshares
Shares
Exercised (in shares)	(128,192)
2009 Plan | Stock Options
Shares
Options outstanding at the beginning of the period (in shares)	249,178
Exercised (in shares)	(68,538)
Forfeited (in shares)	0
Options outstanding at the end of the period (in shares)	180,640
Weighted average exercise price per share
Options outstanding at the beginning of the period (in dollars per share) | $ / shares	$ 122.17
Exercised (in dollars per share) | $ / shares	116.37
Forfeited (in dollars per share) | $ / shares	0
Options outstanding at the end of the period (in dollars per share) | $ / shares	$ 124.37
1994 Plan | Stock Options
Shares
Options outstanding at the beginning of the period (in shares)	82,195
Exercised (in shares)	(59,654)
Forfeited (in shares)	0
Options outstanding at the end of the period (in shares)	22,541
Weighted average exercise price per share
Options outstanding at the beginning of the period (in dollars per share) | $ / shares	$ 103.27
Exercised (in dollars per share) | $ / shares	112.85
Forfeited (in dollars per share) | $ / shares	0
Options outstanding at the end of the period (in dollars per share) | $ / shares	$ 77.91

Stock-Based Compensation Plan42

Stock-Based Compensation Plans (Details 2) - Performance Shares	9 Months Ended
	Sep. 30, 2016$ / sharesshares
Performance awards
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number (in shares)	238,266
Restricted stock granted (in shares)	94,054
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Increase (Decrease) in Awards Based on Performance (in shares)	36,091
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Converted to Restricted Stock (in shares)	(115,618)
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeited in Period (in shares)	(1,630)
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number (in shares)	251,163
Weighted average grant date fair value per award
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value (in dollars per share) | $ / shares	$ 119.65
Grant date fair value per share (in dollars per share) | $ / shares	141.92
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Change in Awards Based on Performance, Weighted Average Grant Date Fair Value (in dollars per share) | $ / shares	101.52
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Converted to Restricted Stock, Weighted Average Grant Date Fair Value (in dollars per share) | $ / shares	94.67
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeitures, Weighted Average Grant Date Fair Value (in dollars per share) | $ / shares	141.98
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value (in dollars per share) | $ / shares	$ 136.74
Share-based Compensation Arrangement By Share-Based Payment Award, Equity Instruments Other Than Options, Grants In Period Based On Total Shareholder Metrics (in shares)	61,039
Share-based Compensation Arrangement By Share-Based Payment Award, Equity Instruments Other Than Options, Grants In Period Based On Financial Metrics (in shares)	33,015

Stock-Based Compensation Plan43

Stock-Based Compensation Plans Stock-Based Compensation Plans (Details 3) - Performance Shares	9 Months Ended
	Sep. 30, 2016$ / shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Dividend yield (as a percent)	3.30%
Estimated volatility, Minimum (as a percent)	15.20%
Estimated volatility, Maximum (as a percent)	22.80%
Risk-free interest rate, minimum (as a percent)	0.44%
Risk-free interest rate, maximum (as a percent)	0.88%
Average estimated fair value (in dollars per share)	$ 131.24
Historical volatility (as a percent)	50.00%
Implied volatility (as a percent)	50.00%

Stock-Based Compensation Plan44

Stock-Based Compensation Plans Stock-Based Compensation Plans (Details 4) - $ / shares	9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015
Restricted Stock [Member]
Restricted stock shares
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number (in shares)	147,884
Restricted stock granted (in shares)	80,873	61,953
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period (in shares)	(84,623)
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeited in Period (in shares)	(3,453)
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number (in shares)	140,681
Restricted stock shares weighted average grant date fair value per share
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value (in dollars per share)	$ 146.21
Grant date fair value per share (in dollars per share)	162.34
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period, Weighted Average Grant Date Fair Value (in dollars per share)	141.49
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeitures, Weighted Average Grant Date Fair Value (in dollars per share)	162.34
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value (in dollars per share)	$ 157.49
Restricted Stock Converted From Performance Shares [Member]
Restricted stock shares
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number (in shares)	98,347
Restricted stock granted (in shares)	115,618	95,826
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period (in shares)	(36,872)
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeited in Period (in shares)	(395)
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number (in shares)	176,698

Stock-Based Compensation Plan45

Stock-Based Compensation Plans (Details 5) - USD ($) $ / shares in Units, $ in Thousands	9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015
Additional disclosures
Stock-based compensation expense	$ 11,555	$ 11,255
Capitalized stock-based compensation cost	$ 7,790	$ 7,738
Performance Shares
Additional disclosures
Grant date value (in dollars per share)	$ 161.66
Restricted stock and restricted stock units
Additional disclosures
Unrecognized compensation cost for unvested restricted stock	$ 28,890
Weighted average period for recognition of unrecognized compensation cost	3 years 7 months 6 days

Related Party Arrangements (Det

Related Party Arrangements (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015
Related Party Arrangements
Management Fees Revenue	$ 1,320	$ 2,161	$ 4,310	$ 7,714
Compensation expense			$ 11,555	$ 11,255
Non Employee Director [Member] | Restricted stock and deferred stock awards
Related Party Arrangements
Restricted stock granted (in shares)			44,327	46,589
Unconsolidated real estate entities
Related Party Arrangements
Outstanding receivables	9,983		$ 9,983		$ 3,832
Non Employee Director [Member] | Restricted stock and deferred stock awards
Related Party Arrangements
Compensation expense	260	$ 293	877	$ 842
Amount of deferred compensation	$ 693		$ 693		$ 488

Fair Value (Details)

Fair Value (Details)	1 Months Ended	3 Months Ended		9 Months Ended		21 Months Ended
	May 31, 2016USD ($)	Sep. 30, 2016USD ($)derivative	Sep. 30, 2015USD ($)	Sep. 30, 2016USD ($)derivative	Sep. 30, 2015USD ($)	Sep. 30, 2016USD ($)derivative
Derivative instruments and Hedging Activities
Payments for Hedge, Financing Activities				$ 14,847,000	$ 0
Income (loss) on cash flow hedges		$ 719,000	$ (31,000)	(73,826,000)	$ (67,000)
Estimated hedging losses to be reclassified from accumulated other comprehensive loss into earnings within the next twelve months				$ 6,978,000
Cash Flow Hedges
Derivative instruments and Hedging Activities
Number of derivative instruments held | derivative		11		11		11
Interest Rate Cap [Member] | Cash Flow Hedges
Derivative instruments and Hedging Activities
Notional amount		$ 36,108,000		$ 36,108,000		$ 36,108,000
Weighted average interest rate (as a percent)		2.70%		2.70%		2.70%
Weighted average capped interest rate (as a percent)		5.90%		5.90%		5.90%
Interest Rate Swap [Member] | Cash Flow Hedges
Derivative instruments and Hedging Activities
Notional amount		$ 800,000,000		$ 800,000,000		$ 800,000,000
Weighted average capped interest rate (as a percent)		2.30%		2.30%		2.30%
Notional amounts entered into during period				$ 600,000,000		$ 1,200,000,000
Derivative, Notional Amounts Settled During Period	$ 400,000,000
Not Designated as Hedging Instrument [Member]
Derivative instruments and Hedging Activities
Number of derivative instruments held | derivative		15		15		15
Not Designated as Hedging Instrument [Member] | Interest Rate Cap [Member]
Derivative instruments and Hedging Activities
Notional amount		$ 722,943,000		$ 722,943,000		$ 722,943,000
Weighted average interest rate (as a percent)		2.60%		2.60%		2.60%
Weighted average capped interest rate (as a percent)		6.20%		6.20%		6.20%

Fair Value (Details 2)

Fair Value (Details 2) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Fair Value Disclosures [Abstract]
Cash flow hedge losses reclassified to earnings	$ (1,748)	$ (1,373)	$ (4,682)	$ (4,401)

Fair Value (Details 3)

Fair Value (Details 3) - Recurring basis - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Estimate of Fair Value Measurement [Member]
Financial Instruments Measured/Discussed at Fair Value
DownREIT units	$ (1,334)	$ (1,381)
Total	(7,036,547)	(6,372,867)
Estimate of Fair Value Measurement [Member] | Unsecured notes
Financial Instruments Measured/Discussed at Fair Value
Indebtedness	(3,988,324)	(3,668,417)
Estimate of Fair Value Measurement [Member] | Secured Debt and Variable Rate Unsecured Term Loan [Member]
Financial Instruments Measured/Discussed at Fair Value
Indebtedness	(2,985,133)	(2,700,341)
Estimate of Fair Value Measurement [Member] | Interest Rate Cap [Member] | Cash Flow Hedges
Financial Instruments Measured/Discussed at Fair Value
Derivative assets	0	5
Estimate of Fair Value Measurement [Member] | Interest Rate Cap [Member] | Not Designated as Hedging Instrument [Member]
Financial Instruments Measured/Discussed at Fair Value
Derivative assets	16	26
Estimate of Fair Value Measurement [Member] | Interest Rate Swap [Member] | Cash Flow Hedges
Financial Instruments Measured/Discussed at Fair Value
Derivative assets	(53,591)	5,422
Estimate of Fair Value Measurement [Member] | Put Option [Member]
Financial Instruments Measured/Discussed at Fair Value
Fair value of remaining outstanding Puts	(8,181)	(8,181)
Fair Value, Inputs, Level 1 [Member]
Financial Instruments Measured/Discussed at Fair Value
DownREIT units	(1,334)	(1,381)
Total	(3,989,658)	(3,669,798)
Fair Value, Inputs, Level 1 [Member] | Unsecured notes
Financial Instruments Measured/Discussed at Fair Value
Indebtedness	(3,988,324)	(3,668,417)
Fair Value, Inputs, Level 2 [Member]
Financial Instruments Measured/Discussed at Fair Value
Total	(3,038,708)	(2,694,888)
Fair Value, Inputs, Level 2 [Member] | Secured Debt and Variable Rate Unsecured Term Loan [Member]
Financial Instruments Measured/Discussed at Fair Value
Indebtedness	(2,985,133)	(2,700,341)
Fair Value, Inputs, Level 2 [Member] | Interest Rate Cap [Member] | Cash Flow Hedges
Financial Instruments Measured/Discussed at Fair Value
Derivative assets	0	5
Fair Value, Inputs, Level 2 [Member] | Interest Rate Cap [Member] | Not Designated as Hedging Instrument [Member]
Financial Instruments Measured/Discussed at Fair Value
Derivative assets	16	26
Fair Value, Inputs, Level 2 [Member] | Interest Rate Swap [Member] | Cash Flow Hedges
Financial Instruments Measured/Discussed at Fair Value
Derivative assets	(53,591)	5,422
Fair Value, Inputs, Level 3 [Member]
Financial Instruments Measured/Discussed at Fair Value
Total	(8,181)	(8,181)
Fair Value, Inputs, Level 3 [Member] | Put Option [Member]
Financial Instruments Measured/Discussed at Fair Value
Fair value of remaining outstanding Puts	$ (8,181)	$ (8,181)

Subsequent Events (Details)

Subsequent Events (Details)	1 Months Ended			9 Months Ended
	Nov. 04, 2016USD ($)communityhome	Oct. 31, 2016USD ($)	Sep. 30, 2016USD ($)	Sep. 30, 2016USD ($)community	Sep. 30, 2015USD ($)	May 31, 2016
Subsequent Event [Line Items]
Debt Instrument, Interest Rate, Stated Percentage						2.95%
Repayments of Unsecured Debt				$ 250,000,000	$ 0
Number of Apartment Communities Sold | community				5
Subsequent Event [Member]
Subsequent Event [Line Items]
Number of Apartment Communities Sold | community	2
Unsecured Notes 2.90 Percent [Member] | Subsequent Event [Member]
Subsequent Event [Line Items]
Debt Instrument, Face Amount		$ 300,000,000
Proceeds from Issuance of Debt		$ 297,117,000
Debt Instrument, Interest Rate, Stated Percentage		2.90%
Unsecured Notes 3.90 Percent [Member] | Subsequent Event [Member]
Subsequent Event [Line Items]
Debt Instrument, Face Amount		$ 350,000,000
Proceeds from Issuance of Debt		$ 345,520,000
Debt Instrument, Interest Rate, Stated Percentage		3.90%
Unsecured notes
Subsequent Event [Line Items]
Repayments of Unsecured Debt			$ 250,000,000
Long-term Debt, Percentage Bearing Fixed Interest, Percentage Rate			5.75%	5.75%
Unsecured notes | Subsequent Event [Member]
Subsequent Event [Line Items]
Repayments of Unsecured Debt	$ 250,000,000
Long-term Debt, Percentage Bearing Fixed Interest, Percentage Rate	5.70%
Avalon Brandemoor I and II [Member] | Subsequent Event [Member]
Subsequent Event [Line Items]
Number of Apartment Homes Sold | home	506
Proceeds from Sale of Real Estate	$ 132,000,000