Organization, Basis of Presentation and Significant Accounting Policies (Policies)	3 Months Ended
	Mar. 31, 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 March 31, 2016, the Company owned or held a direct or indirect ownership interest in 258 operating apartment communities containing 75,379 apartment homes in 10 states and the District of Columbia, of which eleven communities containing 3,429 apartment homes were under reconstruction. In addition, the Company owned or held a direct or indirect interest in 24 communities under construction that are expected to contain an aggregate of 7,670 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 30 communities that, if developed as expected, will contain an estimated 9,745 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 months ended March 31, 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.
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. 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 is aware that third parties incurred significant property damage and are claiming other losses, such as relocation costs, as a result of the fire. The Company has established protocols for processing claims and has encouraged any party who sustained a loss to contact the Company’s insurance carrier to file a claim. To date, four putative class action lawsuits have been filed against the Company on behalf of Edgewater residents and others who may have been harmed by the fire. The court has consolidated these actions in the United States District Court for the District of New Jersey. In addition, 19 lawsuits representing approximately 138 individual plaintiffs have been filed in the Superior Court of New Jersey Bergen County - Law Division. Most of these cases have been consolidated by the court and the Company expects all of them to be consolidated shortly. The Company believes that it has meritorious defenses to the extent of damages claimed. Having incurred applicable deductibles, the Company currently believes that all of its remaining liability to third parties will be substantially covered by its 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’ financial statements to conform to current year presentations as a result of changes in held for sale classification.
Recently Adopted Accounting Standards	Recently Issued Accounting Standards 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