Partners' Capital of Mid-America Apartments, L.P. (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Schedule of Capital Structure [Line Items]
Operating partnership units outstanding	117,886,987	117,792,242
General Partners' Capital Account, Units Outstanding	113,745,207	113,574,798
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	4,141,780
Noncontrolling Interest [Member]
Schedule of Capital Structure [Line Items]
Common Shares Issuable Upon Conversion Of Convertible Stock	4,141,780	4,217,444
Limited Partners' Capital Account	$ 377.9	$ 429.1
Redeemable Capital Shares Par Or Stated Value Per Share	$ 91.24	$ 101.74