Financial Instruments and Derivatives - Additional Information (Details) - USD ($) $ / shares in Units, $ in Millions		9 Months Ended
		Sep. 30, 2021	Dec. 31, 2020
Derivative [Line Items]
Preferred Stock, Redemption Price Per Share	[1]	$ 50.00
Preferred Stock, Redemption Date		Oct. 01, 2026
Designated as Hedging Instrument | Interest Expense
Derivative [Line Items]
Realized losses associated with terminated interest rate swaps that were designated as cash flow hedging instruments		$ 11.7
Change in fair value of interest rate derivatives included in AOCI and expected to be reclassified in the next 12 months		1.1
Fair Value, Measurements, Recurring [Member]
Derivative [Line Items]
Embedded Derivative, Fair Value of Embedded Derivative Asset		$ 50.5	$ 39.0
Conventional Variable Rate Debt [Member] | Maximum [Member]
Derivative [Line Items]
Debt Renewal Period		30 days
Fixed Rate Debt [Member]
Derivative [Line Items]
Notes Payable Excluding Interest Rate Swaps and Cap Agreements		$ 4,500.0	4,400.0
Notes Payable, Fair Value Disclosure		4,900.0	4,900.0
Floating Rate Debt [Member]
Derivative [Line Items]
Notes Payable Excluding Interest Rate Swaps and Cap Agreements		25.0	172.0
Notes Payable, Fair Value Disclosure		$ 25.0	$ 172.0

[1] The redemption price is the price at which the preferred stock is redeemable, at MAA’s option, for cash.