Partners' Capital of Mid-America Apartments, L.P. (Details) - USD ($) $ / shares in Units, $ in Millions	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Schedule of Capital Structure [Line Items]
Operating partnership units outstanding	117,827,046	79,685,786
General Partners' Capital Account, Units Outstanding	113,627,014	75,542,583
Limited Liability (LLC) or Limited Partnership (LP), Managing Member or General Partner, Ownership Interest	96.40%
Percentage Of Ownership Interests	100.00%
Limited Liability Company (LLC) or Limited Partnership (LP), Managing Member or General Partner, Ownership Interest		94.80%
Limited Partners' Capital Account, Units Outstanding	4,200,032
Noncontrolling Interest [Member]
Schedule of Capital Structure [Line Items]
Common Shares Issuable Upon Conversion Of Convertible Stock	4,200,032	4,143,203
Limited Partners' Capital Account	$ 448.9	$ 389.4
Redeemable Capital Shares Par Or Stated Value Per Share	$ 106.88	$ 93.99