Number of apartment communities.

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Percentage points added to the reference rate to compute the variable rate on the debt instrument.

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Face (par) amount of debt instrument at time of issuance.

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Effective interest rate for the funds borrowed under the debt agreement considering interest compounding and original issue discount or premium.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Date when the debt instrument is scheduled to be fully repaid, in CCYY-MM-DD format.

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Description of the payment terms of the debt instrument (for example, whether periodic payments include principal and frequency of payments) and discussion about any contingencies associated with the payment.

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Period of time between issuance and maturity of debt instrument, in PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Amount of unused borrowing capacity under the long-term financing arrangement that is available to the entity as of the balance sheet date.

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The total amount of the contingent obligation under letters of credit outstanding as of the reporting date.

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The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

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Amount of current borrowing capacity under the credit facility considering any current restrictions on the amount that could be borrowed (for example, borrowings may be limited by the amount of current assets), but without considering any amounts currently outstanding under the facility.

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Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

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Amount of investment in mortgage loan on real estate by entity with substantial portion of business acquiring and holding investment real estate or interest in real estate.

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The cash outflow to repay long-term debt that is wholly or partially secured by collateral. Excludes repayments of tax exempt secured debt.

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Borrowings - Additional Information (Details)	1 Months Ended	3 Months Ended
Borrowings - Additional Information (Details)	Feb. 28, 2021 USD ($) ApartmentUnit	Mar. 31, 2021 USD ($)
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Effective Percentage		3.40%
Commercial Paper Notes [Member]
Debt Instrument [Line Items]
Debt Instrument, Payment Terms		397
Debt Instrument, Face Amount		$ 385,000,000.0
Debt Instrument, Unused Borrowing Capacity, Amount		298,100,000
Maximum [Member] \| Commercial Paper Notes [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount		$ 500,000,000.0
Unsecured Debt [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Effective Percentage		3.30%
Unsecured Debt [Member] \| Fixed Rate Debt Senior Notes [Member]
Debt Instrument [Line Items]
Debt Instrument, Maturity Date		Jan. 27, 2027
Debt Instrument, Face Amount		$ 3,922,000,000
Debt Instrument, Interest Rate, Effective Percentage		3.60%
Unsecured Debt [Member] \| Years to Maturity [Member] \| Fixed Rate Debt Senior Notes [Member]
Debt Instrument [Line Items]
Debt Instrument, Term		5 years 9 months 18 days
Unsecured Debt [Member] \| Minimum [Member] \| Fixed Rate Debt Senior Notes [Member]
Debt Instrument [Line Items]
Debt Instrument, Term		10 years
Unsecured Debt [Member] \| Maximum [Member] \| Fixed Rate Debt Senior Notes [Member]
Debt Instrument [Line Items]
Debt Instrument, Term		12 years
Unsecured Debt [Member] \| $1 Billion Unsecured Revolving Credit Faciltiy [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Current Borrowing Capacity		$ 1,000,000,000.0
Line of Credit Facility, Maximum Borrowing Capacity		$ 1,500,000,000
Debt Instrument, Maturity Date		May 31, 2023
Line of Credit Facility, Amount Outstanding		$ 0
Letters of Credit Outstanding, Amount		$ 3,400,000
Unsecured Debt [Member] \| $1 Billion Unsecured Revolving Credit Faciltiy [Member] \| Minimum [Member]
Debt Instrument [Line Items]
Debt Instrument, Basis Spread on Variable Rate		0.75%
Unsecured Debt [Member] \| $1 Billion Unsecured Revolving Credit Faciltiy [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Basis Spread on Variable Rate		1.45%
Unsecured Debt [Member] \| Public Income Notes [Member] \| Fixed Rate Debt Senior Notes [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount		$ 3,700,000,000
Unsecured Debt [Member] \| Private Placement [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount		222,000,000.0
Unsecured Debt [Member] \| Private Placement [Member] \| Fixed Rate Debt Senior Notes [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount		$ 222,000,000.0
Secured Debt [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Effective Percentage		4.40%
Secured Debt [Member] \| Fixed Rate Debt Senior Notes [Member]
Debt Instrument [Line Items]
Debt Instrument, Maturity Date		Dec. 31, 2048
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate		$ 369,600,000
Debt Instrument, Interest Rate, Effective Percentage		4.40%
Maturing July 2020, Three Property Mortgage [Member] \| Secured Debt [Member]
Debt Instrument [Line Items]
Repayments of Secured Debt	$ 118,600,000
Number of Apartment Communities \| ApartmentUnit	8