Investments	9 Months Ended
Investments	Sep. 30, 2022
Equity Method Investments and Joint Ventures [Abstract]
Investments	Investments Unconsolidated Investments As of September 30, 2022, the Company had investments in seven unconsolidated real estate entities with ownership interest percentages ranging from 20.0% to 50.0% and other unconsolidated investments including property technology and environmentally focused companies and investment management funds. The Company accounts for its investments in unconsolidated entities under the equity method of accounting or under the measurement alternative with the carrying amount of the investment adjusted to fair value when there is an observable transaction for the same or similar investment of the same issuer indicating a change in fair value. The significant accounting policies of the Company's unconsolidated real estate investments are consistent with those of the Company in all material respects. Certain of these investments are subject to various buy‑sell provisions or other rights which are customary in real estate joint venture agreements. The Company and its partners in these entities may initiate these provisions to either sell the Company's interest or acquire the interest from the Company's partner. During the nine months ended September 30, 2022, Archstone Multifamily Partners AC LP (the "U.S. Fund") sold its final three communities: •Avalon Grosvenor Tower, located in Bethesda, MD, which contains 237 apartment homes and was sold for $95,250,000. The Company's share of the gain in accordance with GAAP was $9,187,000. In conjunction with the disposition of Avalon Grosvenor Tower, the U.S. Fund repaid a $39,060,000 secured note at par. •Avalon Studio 4121, located in Studio City, CA, which contains 149 apartment homes and was sold for $76,000,000. The Company's share of the gain in accordance with GAAP was $9,236,000. In conjunction with the disposition of Avalon Studio 4121, the U.S. Fund repaid a $25,768,000 secured note at par. •Avalon Station 250, located in Dedham, MA, which contains 285 apartment homes and was sold for $142,250,000. The Company's share of the gain in accordance with GAAP was $19,639,000. In advance of the disposition of Avalon Station 250, the U.S. Fund repaid a $50,385,000 secured note at par. The Company has an equity interest of 28.6% in the U.S. Fund, and during the three months ended September 30, 2022, in conjunction with the final dispositions, achieved a threshold return resulting in an incentive distribution for the promoted interest based on the returns earned by the U.S. Fund. During the three months ended September 30, 2022, the Company recognized income of $4,690,000 for the promoted interest, which is reported as a component of income from investments in unconsolidated entities on the accompanying Condensed Consolidated Statements of Comprehensive Income. Investments in Consolidated Real Estate Entities During the nine months ended September 30, 2022, the Company acquired three wholly-owned communities: •Avalon Flatirons, located in Lafayette, CO, which contains 207 apartment homes and 16,000 square feet of commercial space, was acquired for $95,000,000. •Waterford Court, located in Addison, TX, which contains 196 apartment homes, was acquired for $69,500,000. •Avalon Miramar Park Place, located in Miramar, FL, which contains 650 apartment homes, was acquired for $295,000,000. The Company accounted for these purchases as asset acquisitions and recorded the acquired assets and assumed liabilities, including identifiable intangibles, at their relative fair values based on the purchase price and acquisition costs incurred. The Company used third party pricing or internal models for the value of the land, a valuation model for the value of the building, and an internal model to determine the fair value of the remaining real estate assets and in-place leases. Given the heterogeneous nature of multifamily real estate, the fair values for the land, debt, real estate assets and in-place leases incorporated significant unobservable inputs and therefore are considered to be Level 3 prices within the fair value hierarchy. Structured Investment Program In April 2022, the Company established its Structured Investment Program (the “SIP”), a new investment platform through which the Company provides mezzanine loans or preferred equity to third-party multifamily developers. During the nine months ended September 30, 2022, the Company entered into commitments for three mezzanine loans of up to $92,375,000 in the aggregate. These commitments are to fund multifamily development projects in the Company's existing markets. At September 30, 2022, the Company had funded $15,514,000 of these commitments. The Company evaluates each commitment under the SIP to determine the classification as a loan or an investment in a real estate development project. As of September 30, 2022, all of the commitments under the SIP are classified as loans. The Company includes amounts outstanding under the SIP as a component of prepaid expenses and other assets on the accompanying Condensed Consolidated Balance Sheets. The Company evaluates the credit risk for each loan on an ongoing basis, estimating the reserve for credit losses using relevant available information from internal and external sources. Market-based historical credit loss data provides the basis for the estimation of expected credit losses, with adjustments, if necessary, for differences in current loan-specific risk characteristics, such as the amount of equity capital provided by a borrower, nature of the real estate being developed or other factors. For the three existing loans, interest is recognized as earned as interest income, included as a component of interest expense, net, on the accompanying Condensed Consolidated Statements of Comprehensive Income. Expensed Transaction, Development and Other Pursuit Costs The Company capitalizes pre-development costs incurred in pursuit of new development opportunities when 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. Costs incurred for pursuits for which future development is not yet considered probable are expensed as incurred. In addition, if the status of a Development Right changes, making future development by the Company no longer probable, any non-recoverable capitalized pre-development costs are expensed. The Company expensed $6,514,000 and $417,000 for the three months ended September 30, 2022 and 2021, respectively, and $9,865,000 and $1,900,000 for the nine months ended September 30, 2022 and 2021, respectively, for costs related to development pursuits not yet considered probable for development and the abandonment of Development Rights, as well as costs incurred in pursuing the acquisition or disposition of assets for which such acquisition and disposition activity did not occur. These costs are included in expensed transaction, development and other pursuit costs, net of recoveries on the accompanying Condensed Consolidated Statements of Comprehensive Income. The amount for 2022 includes the write-off of $5,335,000 related to a Development Right in the Pacific Northwest that the Company determined is no longer probable. These costs can vary greatly, and the costs incurred in any given period may be significantly different in future periods. Casualty and Impairment of Long-Lived Assets 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 an asset may not be recoverable, the Company assesses its recoverability by comparing the carrying amount of the 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 asset. Based on periodic tests of recoverability of long-lived assets, the Company did not recognize any impairment losses for the three and nine months ended September 30, 2022 and 2021. During the three and nine months ended September 30, 2021, the Company recognized a charge of $1,971,000 for the property and casualty damages across several communities in its East Coast markets related to severe storms, reported as casualty and impairment loss on the accompanying Condensed Consolidated Statements of Comprehensive Income. In addition, during the nine months ended September 30, 2021, the Company recognized a charge of $1,146,000 for the property and casualty damages resulting from a fire at an operating community, reported as casualty and impairment loss on the accompanying Condensed Consolidated Statements of Comprehensive Income. The Company evaluates its for-sale condominium inventory for potential indicators of impairment, considering whether the fair value of the individual for-sale condominium units exceeds the carrying value of those units. For-sale condominium inventory is stated at the lower of cost or fair value. The Company determines the fair value of its for-sale condominium inventory as the estimated sales price less direct costs to sell. For the three and nine months ended September 30, 2022 and 2021, the Company did not recognize any impairment losses on its for-sale condominium inventory. The Company assesses its portfolio of land held for both development and investment for impairment if the intent of the Company changes with respect to either the development of, or the expected holding period for, the land. During the three and nine months ended September 30, 2022 and 2021, the Company did not recognize any impairment charges on its investment in land. The Company evaluates its unconsolidated investments for other than temporary impairment, considering both the extent and amount by which the carrying value of the investment exceeds the fair value, and the Company's intent and ability to hold the investment to recover its carrying value. The Company also evaluates its proportionate share of any impairment of assets held by unconsolidated investments. There were no other than temporary impairment losses recognized for any of the Company's investments in unconsolidated real estate entities during the three and nine months ended September 30, 2022 and 2021.