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v3.20.4

Borrowings - Additional Information (Details) | 1 Months Ended | 12 Months Ended |
--- | --- | --- | ---
Aug. 31, 2020 USD ($) | Jul. 31, 2020 USD ($) ApartmentUnit | Dec. 31, 2020 USD ($) | Dec. 31, 2019 USD ($)
Debt Instrument [Line Items] |  |  |  |
Debt Instrument, Interest Rate, Effective Percentage |  |  | 3.60% |
Commercial Paper Notes [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Debt Instrument, Payment Terms |  |  | 397 |
Debt Instrument, Face Amount |  |  | $ 172,000,000.0 |
Maximum [Member] | Commercial Paper Notes [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Debt Instrument, Face Amount |  |  | $ 500,000,000.0 |
Secured Debt [Member] | Fixed Rate Debt Senior Notes [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Debt Instrument, Maturity Date |  |  | Dec. 31, 2042 |
Debt Instrument, Interest Rate, Effective Percentage |  |  | 4.60% |
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate |  |  | $ 488,700,000 |
Unsecured Debt [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Debt Instrument, Interest Rate, Effective Percentage |  |  | 3.50% |
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 | $ 3,472,000,000
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 |  |  | 6 years 1 month 6 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 |
Unsecured Debt [Member] | 1.700% Notes Due 2031 [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Debt Instrument, Payment Terms | Interest on the 2031 Notes is payable on February 15 and August 15 of each year, beginning on February 15, 2021. |  |  |
Debt Instrument, Face Amount | $ 450,000,000.0 |  |  |
Debt Instrument, Interest Rate, Stated Percentage | 1.70% |  |  |
Debt Instrument, Interest Rate, Effective Percentage | 1.76% |  |  |
Debt Instrument, Redemption Price, Percentage | 99.465% |  |  |
Debt Issuance Costs, Gross | $ 5,300,000 |  |  |
Proceeds from Debt, Net of Issuance Costs | 444,700,000 |  |  |
Unsecured Debt [Member] | Wells Fargo Term Loan [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Repayments of Unsecured Debt | $ 300,000,000.0 |  |  |
Maturing July 2020, Three Property Mortgage [Member] | Secured Debt [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Repayments of Secured Debt |  | $ 63,600,000 |  |
Number of Apartment Communities | ApartmentUnit |  | 3 |  |
Maturing July 2020, Four Property Mortgage [Member] | Secured Debt [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Repayments of Secured Debt |  | $ 72,200,000 |  |
Number of Apartment Communities | ApartmentUnit |  | 4 |  |

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- Definition Amount, before accumulated amortization, of debt issuance costs. Includes, but is not limited to, legal, accounting, underwriting, printing, and registration costs. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 835 -SubTopic 30 -Section 45 -Paragraph 3 -URI http://asc.fasb.org/extlink&oid=119993939&loc=d3e28555-108399 + Details
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- Definition 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. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(22)) -URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03(16)) -URI http://asc.fasb.org/extlink&oid=120398452&loc=d3e534808-122878 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-03(16)) -URI http://asc.fasb.org/extlink&oid=120400017&loc=d3e572229-122910 + Details
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