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Financial Instruments and Derivatives - Additional Information (Details) $ / shares in Units, $ in Millions | 9 Months Ended |
--- | --- | ---
Sep. 30, 2020 USD ($) Contract $ / shares | Dec. 31, 2019 USD ($)
Derivative [Line Items] |  |  |
Preferred Stock, Redemption Price Per Share | $ / shares | [1] | $ 50.00 |
Preferred Stock, Redemption Date |  | Oct. 01, 2026 |
Designated as Hedging Instrument | Interest Expense |  |  |
Derivative [Line Items] |  |  |
Change in fair value of interest rate derivatives included in AOCI and expected to be reclassified in the next 12 months |  | $ 1.1 |
Designated as Hedging Instrument | Interest Rate Swap [Member] |  |  |
Derivative [Line Items] |  |  |
Derivative, Number of Instruments Held | Contract |  | 0 |
Fair Value, Measurements, Recurring [Member] |  |  |
Derivative [Line Items] |  |  |
Embedded Derivative, Fair Value of Embedded Derivative Asset |  | $ 21.9 | $ 36.5
Fair Value, Measurements, Recurring [Member] | Other Assets [Member] |  |  |
Derivative [Line Items] |  |  |
Interest Rate Derivative Assets, at Fair Value |  |  | 0.1
Conventional Variable Rate Debt [Member] | Minimum [Member] |  |  |
Derivative [Line Items] |  |  |
Debt Renewal Period |  | 30 days |
Conventional Variable Rate Debt [Member] | Maximum [Member] |  |  |
Derivative [Line Items] |  |  |
Debt Renewal Period |  | 90 days |
Fixed Rate Debt [Member] |  |  |
Derivative [Line Items] |  |  |
Notes Payable Excluding Interest Rate Swaps and Cap Agreements |  | $ 4,400.0 | 4,100.0
Notes Payable, Fair Value Disclosure |  | 4,900.0 | 4,500.0
Floating Rate Debt [Member] |  |  |
Derivative [Line Items] |  |  |
Notes Payable Excluding Interest Rate Swaps and Cap Agreements |  | 35.0 | 370.0
Notes Payable, Fair Value Disclosure |  | $ 35.0 | $ 370.8
[1] | The redemption price is the price at which the preferred stock is redeemable, at MAA’s option, for cash.

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