Partners' Capital of Mid-America Apartments, L.P. (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 01, 2016
Schedule of Capital Structure [Line Items]
Operating partnership units outstanding	118,021,379	117,886,987
General Partners' Capital Account, Units Outstanding	113,916,208	113,745,207
Limited Liability Company (LLC) or Limited Partnership (LP), Managing Member or General Partner, Ownership Interest	96.50%	96.50%
Limited Partners' Capital Account, Units Outstanding	4,105,171
Noncontrolling Interest [Member]
Schedule of Capital Structure [Line Items]
Common Shares Issuable Upon Conversion Of Convertible Stock	4,105,171	4,141,780
Limited Partners' Capital Account	$ 448.8	$ 377.9
Redeemable Capital Shares Par Or Stated Value Per Share	$ 109.33	$ 91.24
Redeemable Preferred Stock [Member]
Schedule of Capital Structure [Line Items]
Preferred Stock, Shares Outstanding			867,846