Partners' Capital of Mid-America Apartments, L.P. (Details) - USD ($) $ / shares in Units, $ in Millions	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Dec. 01, 2016
Schedule of Capital Structure [Line Items]
Operating partnership units outstanding	117,943,960	117,823,412
General Partners' Capital Account, Units Outstanding	113,808,292	113,607,734
Limited Liability (LLC) or Limited Partnership (LP), Managing Member or General Partner, Ownership Interest	96.50%
Limited Liability Company (LLC) or Limited Partnership (LP), Managing Member or General Partner, Ownership Interest		96.40%
Limited Partners' Capital Account, Units Outstanding	4,135,668
Noncontrolling Interest [Member]
Schedule of Capital Structure [Line Items]
Common Shares Issuable Upon Conversion Of Convertible Stock	4,135,668	4,215,678
Limited Partners' Capital Account	$ 416.3	$ 444.2
Redeemable Capital Shares Par Or Stated Value Per Share	$ 100.67	$ 105.38
Redeemable Preferred Stock [Member]
Schedule of Capital Structure [Line Items]
Preferred Stock, Shares Outstanding			867,846