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Organization and Summary of Significant Accounting Policies - Additional Information (Details) $ in Thousands | 3 Months Ended | 9 Months Ended |  |  |  |  |
--- | --- | --- | --- | --- | --- | --- | ---
Sep. 30, 2025 USD ($) Properties State Property Community shares | Sep. 30, 2024 USD ($) shares | Sep. 30, 2025 USD ($) Properties State Property Community shares | Sep. 30, 2024 USD ($) shares | Dec. 31, 2028 Property | Dec. 31, 2027 Property | Dec. 31, 2026 Property | Dec. 31, 2025 Property | Dec. 31, 2024 USD ($) shares
Real Estate Properties [Line Items] |  |  |  |  |  |  |  |  |
General Partners' Capital Account, Units Outstanding | shares | 117,081,742 | 116,880,291 | 117,081,742 | 116,880,291 |  |  |  |  |
Number of Real Estate Properties | Community | 293 |  | 293 |  |  |  |  |  |
Number of units under development community | Properties | 2,242 |  | 2,242 |  |  |  |  |  |
Development and capital improvements in progress | $ 449,390 |  | $ 449,390 |  |  |  |  |  | $ 470,282
Number of States in which Entity Operates | State | 16 |  | 16 |  |  |  |  |  |
Consolidated assets | $ 11,926,585 |  | $ 11,926,585 |  |  |  |  |  | 11,812,369
Consolidated liabilities | 5,912,283 |  | 5,912,283 |  |  |  |  |  | $ 5,664,705
Real Estate Investments, Joint Ventures | $ 22,400 |  | $ 22,400 |  |  |  |  |  |
Percentage Of Rental Revenue From Leasing Of Apartment Homes |  |  | 94.00% |  |  |  |  |  |
Percentage Of Reimbursable Revenue From Leasing Of Apartment Homes |  |  | 5.00% |  |  |  |  |  |
Percentage of Rental Revenue and Other Income From Non-leasing Activities |  |  | 1.00% |  |  |  |  |  |
Operating Lease, Right-of-Use Asset, Statement of Financial Position | Other assets |  | Other assets |  |  |  |  |  | Other assets
Operating Lease, Liability, Statement of Financial Position [Extensible Enumeration] | Accrued expenses and other liabilities |  | Accrued expenses and other liabilities |  |  |  |  |  |
Operating Lease, Right-of-Use Asset | $ 38,700 |  | $ 38,700 |  |  |  |  |  | $ 40,500
Right-of-use Lease, Liability | 24,793 |  | 24,793 |  |  |  |  |  | 26,100
Net proceeds from sale of marketable equity securities |  | $ 3,300 | 0 | $ 9,975 |  |  |  |  |
Net realized / unrealized gain on sale |  | 2,700 |  | 8,300 |  |  |  |  |
Marketable equity securities | 2,700 |  | 2,700 |  |  |  |  |  | 3,300
Marketable Equity Securities [Member] |  |  |  |  |  |  |  |  |
Real Estate Properties [Line Items] |  |  |  |  |  |  |  |  |
Unrealized gains (losses) | (800) | (1,200) | (600) | (5,400) |  |  |  |  |
Limited Partnership [Member] |  |  |  |  |  |  |  |  |
Real Estate Properties [Line Items] |  |  |  |  |  |  |  |  |
Investment Income |  | $ 500 | 6,000 | $ 9,000 |  |  |  |  |
Investment Expense | 4,300 |  |  |  |  |  |  |  |
Other Assets [Member] |  |  |  |  |  |  |  |  |
Real Estate Properties [Line Items] |  |  |  |  |  |  |  |  |
Real Estate Investments, Joint Ventures | 76,000 |  | 76,000 |  |  |  |  |  | 62,200
Real Estate [Member] | Post Massachusetts Avenue [Member] |  |  |  |  |  |  |  |  |
Real Estate Properties [Line Items] |  |  |  |  |  |  |  |  |
Real Estate Investments, Joint Ventures | $ 41,900 |  | $ 41,900 |  |  |  |  |  | $ 41,700
Maximum [Member] | Accounting Standards Update 2016-02 [Member] |  |  |  |  |  |  |  |  |
Real Estate Properties [Line Items] |  |  |  |  |  |  |  |  |
Operating lease, term of contract | 1 year |  | 1 year |  |  |  |  |  |
Development Properties [Member] | Scenario Forecast [Member] |  |  |  |  |  |  |  |  |
Real Estate Properties [Line Items] |  |  |  |  |  |  |  |  |
Number of Real Estate Properties | Property |  |  |  |  | 1 | 1 | 4 | 1 |
Retail [Member] |  |  |  |  |  |  |  |  |
Real Estate Properties [Line Items] |  |  |  |  |  |  |  |  |
Number of Real Estate Properties | Property | 35 |  | 35 |  |  |  |  |  |
M A A L P [Member] |  |  |  |  |  |  |  |  |
Real Estate Properties [Line Items] |  |  |  |  |  |  |  |  |
Limited Liability Company (LLC) or Limited Partnership (LP), Managing Member or General Partner, Ownership Interest |  |  | 97.50% | 97.40% |  |  |  |  |
Limited Partnership [Member] |  |  |  |  |  |  |  |  |
Real Estate Properties [Line Items] |  |  |  |  |  |  |  |  |
General Partners' Capital Account, Units Outstanding | shares | 117,081,742 |  | 117,081,742 |  |  |  |  |  | 116,883,421
Number of Real Estate Properties | Property | 1 |  | 1 |  |  |  |  |  |
Development and capital improvements in progress | $ 449,390 |  | $ 449,390 |  |  |  |  |  | $ 470,282
Consolidated assets | 11,926,585 |  | 11,926,585 |  |  |  |  |  | 11,812,369
Consolidated liabilities | 5,912,302 |  | 5,912,302 |  |  |  |  |  | 5,664,724
Net proceeds from sale of marketable equity securities |  |  | 0 | $ 9,975 |  |  |  |  |
Limited Partnership [Member] | Real Estate [Member] | Variable Interest Entity Primary Beneficiary [Member] |  |  |  |  |  |  |  |  |
Real Estate Properties [Line Items] |  |  |  |  |  |  |  |  |
Consolidated assets | 530,800 |  | 530,800 |  |  |  |  |  | 432,200
Consolidated liabilities | $ 24,200 |  | $ 24,200 |  |  |  |  |  | $ 27,100
Limited Partnership [Member] | Minimum [Member] |  |  |  |  |  |  |  |  |
Real Estate Properties [Line Items] |  |  |  |  |  |  |  |  |
Percentage of ownership interests of all consolidated subsidiaries (percent) | 80.00% |  | 80.00% |  |  |  |  |  |
Limited Partnership [Member] | Maximum [Member] |  |  |  |  |  |  |  |  |
Real Estate Properties [Line Items] |  |  |  |  |  |  |  |  |
Percentage of ownership interests of all consolidated subsidiaries (percent) | 100.00% |  | 100.00% |  |  |  |  |  |
Limited Partnership [Member] | Development Properties [Member] | Costs Incurred To Date [Member] |  |  |  |  |  |  |  |  |
Real Estate Properties [Line Items] |  |  |  |  |  |  |  |  |
Development and capital improvements in progress | $ 543,200 |  | $ 543,200 |  |  |  |  |  |

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