Mid-America Apartments 10-Q 26 Oct 17 2017 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2017	Oct. 23, 2017
Document Information [Line Items]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2017
Document Fiscal Year Focus	2,017
Document Fiscal Period Focus	Q3
Trading Symbol	MAA
Entity Registrant Name	MID AMERICA APARTMENT COMMUNITIES INC
Entity Central Index Key	912,595
Current Fiscal Year End Date	--09-30
Entity Filer Category	Accelerated Filer
Entity Common Stock, Shares Outstanding		113,627,014
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Limited Partner [Member]
Document Information [Line Items]
Entity Registrant Name	MID-AMERICA APARTMENTS, L.P.
Entity Central Index Key	1,581,776
Entity Filer Category	Non-accelerated Filer

MAA Condensed Consolidated Bala

MAA Condensed Consolidated Balance Sheets - Parent Company [Member] - USD ($)	Sep. 30, 2017	Dec. 31, 2016
Assets:
Land	$ 1,828,637,000	$ 1,816,008,000
Buildings and improvements	10,801,863,000	10,523,762,000
Furniture, fixtures and equipment	339,039,000	298,204,000
Development and capital improvements in progress	156,938,000	231,224,000
Real Estate Investment Property, at Cost	13,126,477,000	12,869,198,000
Less accumulated depreciation	(1,967,481,000)	(1,656,071,000)
Real Estate Investment Property, Net	11,158,996,000	11,213,127,000
Undeveloped land	57,285,000	71,464,000
Corporate properties, net	12,367,000	12,778,000
Investments in real estate joint ventures	45,096,000	44,493,000
Real Estate Held-for-sale	5,315,000	0
Real estate assets, net	11,279,059,000	11,341,862,000
Cash and cash equivalents	47,851,000	33,536,000
Restricted cash	80,253,000	88,264,000
Deferred financing costs, net	3,906,000	5,065,000
Other assets	120,493,000	134,525,000
Goodwill	1,239,000	1,239,000
Total assets	11,532,801,000	11,604,491,000
Liabilities:
Unsecured notes payable	3,382,861,000	3,180,624,000
Secured notes payable	1,109,973,000	1,319,088,000
Accounts payable	17,275,000	11,970,000
Fair market value of interest rate swaps	2,602,000	7,562,000
Accrued expenses and other liabilities	439,662,000	414,244,000
Security deposits	18,998,000	18,829,000
Total liabilities	4,971,371,000	4,952,317,000
Redeemable stock	10,804,000	10,073,000
Shareholders' equity:
Preferred Stock, Value, Outstanding	9,000	9,000
Common stock	1,134,000	1,133,000
Additional paid-in capital	7,117,829,000	7,109,012,000
Accumulated distributions in excess of net income	(802,835,000)	(707,479,000)
Accumulated other comprehensive loss	790,000	1,144,000
Total MAA shareholders' equity	6,316,927,000	6,403,819,000
Noncontrolling interest	231,393,000	235,976,000
Total equity	6,548,320,000	6,639,795,000
Noncontrolling Interest in Joint Ventures	2,306,000	2,306,000
Permanent Equity Attributable to Parent and Noncontrolling Interest	6,550,626,000	6,642,101,000
Total liabilities and equity	$ 11,532,801,000	$ 11,604,491,000
Redeemable stock, shares issued and outstanding	101,081	103,578

MAALP Condensed Consolidated Ba

MAALP Condensed Consolidated Balance Sheets - Limited Partner [Member] - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Assets:
Land	$ 1,828,637	$ 1,816,008
Buildings and improvements	10,801,863	10,523,762
Furniture, fixtures and equipment	339,039	298,204
Development and capital improvements in progress	156,938	231,224
Real Estate Investment Property, at Cost	13,126,477	12,869,198
Less accumulated depreciation	(1,967,481)	(1,656,071)
Real Estate Investment Property, Net	11,158,996	11,213,127
Undeveloped land	57,285	71,464
Corporate properties, net	12,367	12,778
Investments in real estate joint ventures	45,096	44,493
Real Estate Held-for-sale	5,315	0
Real estate assets, net	11,279,059	11,341,862
Cash and cash equivalents	47,851	33,536
Restricted cash	80,253	88,264
Deferred financing costs, net	3,906	5,065
Other assets	120,493	134,525
Goodwill	1,239	1,239
Total assets	11,532,801	11,604,491
Liabilities:
Unsecured notes payable	3,382,861	3,180,624
Secured notes payable	1,109,973	1,319,088
Accounts payable	17,275	11,970
Fair market value of interest rate swaps	2,602	7,562
Accrued expenses and other liabilities	439,662	414,244
Security deposits	18,998	18,829
Due to general partner	19	19
Total liabilities	4,971,390	4,952,336
Redeemable units	10,804	10,073
Capital [Abstract]
Preferred Units, Preferred Partners' Capital Accounts	66,840	64,833
General Partners' Capital Account	6,249,190	6,337,721
Limited Partners' Capital Account	231,393	235,976
Accumulated other comprehensive loss	878	1,246
Noncontrolling Interest in Joint Ventures	2,306	2,306
Capital	6,548,301	6,639,776
Partners' Capital, Including Portion Attributable to Noncontrolling Interest	6,550,607	6,642,082
Total Liabilities and Capital	$ 11,532,801	$ 11,604,491
Redeemable units, units issued and outstanding	101,081	103,578

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets (Parenthetical) - $ / shares	Sep. 30, 2017	Dec. 31, 2016
Common stock, shares outstanding	113,627,014
General Partners' Capital Account, Units Outstanding	113,627,014
Limited Partners' Capital Account, Units Outstanding	4,200,032
Preferred Stock, Shares Issued	867,846
Preferred Stock, Shares Outstanding	867,846
Preferred Stock, Liquidation Preference Per Share	$ 50
Limited Partner [Member]
General Partners' Capital Account, Units Outstanding	113,627,014	113,518,212
Limited Partners' Capital Account, Units Outstanding	4,200,032	4,220,403
Preferred Units, Issued	867,846	867,846
Preferred Units, Outstanding	867,846	867,846
Parent Company [Member]
Common stock, par value per share	$ 0.01	$ 0.01
Common stock, shares authorized	145,000,000	145,000,000
Common stock, shares issued	113,627,014	113,518,212
Common stock, shares outstanding	113,627,014	113,518,212
Preferred Stock, Par or Stated Value Per Share	$ 0.01	$ 0.01
Preferred Stock, Shares Authorized	20,000,000	20,000,000
Preferred Stock, Shares Issued	867,846	867,846
Preferred Stock, Shares Outstanding	867,846	867,846
Preferred Stock, Liquidation Preference Per Share	$ 50	$ 50

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Limited Partner [Member]
Operating revenues:
Rental revenues	$ 357,619	$ 254,161	$ 1,064,628	$ 749,153
Other property revenues	26,931	22,737	81,621	68,997
Total operating revenues	384,550	276,898	1,146,249	818,150
Property operating expenses:
Personnel	35,640	27,236	103,655	78,290
Building repairs and maintenance	12,663	9,377	34,287	23,156
Real estate taxes and insurance	52,597	34,282	160,733	104,182
Utilities	30,175	24,690	84,599	69,070
Landscaping	4,809	4,021	18,376	15,016
Other operating	13,295	7,040	34,771	20,768
Depreciation and amortization	117,928	76,959	374,285	227,829
Total property operating expenses	267,107	183,605	810,706	538,311
Acquisition expense	0	1,033	0	2,167
Property management expenses	10,281	7,908	32,007	25,221
General and administrative expenses	8,361	6,661	30,735	20,257
Merger Related Expenses	128	3,901	3,977	3,901
Business Combination, Integration Related Costs	4,002	0	10,521	0
Income from continuing operations before non-operating items	94,671	73,790	258,303	228,293
Interest and other non-property (expense) income	4,303	64	7,632	159
Interest expense	(39,940)	(32,168)	(115,005)	(96,418)
Loss on debt extinguishment	828	0	3,168	3
Net casualty loss after insurance and other settlement proceeds	564	(75)	233	738
Gain on sale of depreciable real estate assets excluded from discontinued operations	58,844	47,749	59,045	48,572
Gain on sale of non-depreciable real estate assets	(6)	0	42	2,170
Income before income tax expense	119,264	89,360	213,418	183,517
Income tax expense	(641)	(454)	(1,910)	(1,200)
Income from continuing operations before joint venture activity	118,623	88,906	211,508	182,317
Gain (loss) from real estate joint ventures	335	0	1,021	27
Consolidated net income	118,958	88,906	212,529	182,344
Preferred Unit Dividends, Income Statement Impact	922	0	2,766	0
Net income available for Mid-America Apartments, L.P. common unitholders	$ 118,036	$ 88,906	$ 209,763	$ 182,344
Earnings per common share - basic:
Net income available for common shareholders	$ 1	$ 1.12	$ 1.78	$ 2.29
Earnings per common share - diluted:
Net income available for common shareholders	1	1.12	1.78	2.29
Distribution Made to Limited Partner, Distributions Declared, Per Unit	$ 0.87	$ 0.82	$ 2.61	$ 2.46
Parent Company [Member]
Operating revenues:
Rental revenues	$ 357,619	$ 254,161	$ 1,064,628	$ 749,153
Other property revenues	26,931	22,737	81,621	68,997
Total operating revenues	384,550	276,898	1,146,249	818,150
Property operating expenses:
Personnel	35,640	27,236	103,655	78,290
Building repairs and maintenance	12,663	9,377	34,287	23,156
Real estate taxes and insurance	52,597	34,282	160,733	104,182
Utilities	30,175	24,690	84,599	69,070
Landscaping	4,809	4,021	18,376	15,016
Other operating	13,295	7,040	34,771	20,768
Depreciation and amortization	117,928	76,959	374,285	227,829
Total property operating expenses	267,107	183,605	810,706	538,311
Acquisition expense	0	1,033	0	2,167
Property management expenses	10,281	7,908	32,007	25,221
General and administrative expenses	8,361	6,661	30,735	20,257
Merger Related Expenses	128	3,901	3,977	3,901
Business Combination, Integration Related Costs	4,002	0	10,521	0
Income from continuing operations before non-operating items	94,671	73,790	258,303	228,293
Interest and other non-property (expense) income	4,303	64	7,632	159
Interest expense	(39,940)	(32,168)	(115,005)	(96,418)
Loss on debt extinguishment	828	0	3,168	3
Net casualty loss after insurance and other settlement proceeds	564	(75)	233	738
Gain on sale of depreciable real estate assets excluded from discontinued operations	58,844	47,749	59,045	48,572
Gain on sale of non-depreciable real estate assets	(6)	0	42	2,170
Income before income tax expense	119,264	89,360	213,418	183,517
Income tax expense	(641)	(454)	(1,910)	(1,200)
Income from continuing operations before joint venture activity	118,623	88,906	211,508	182,317
Gain (loss) from real estate joint ventures	335	0	1,021	27
Consolidated net income	118,958	88,906	212,529	182,344
Net income attributable to noncontrolling interests	4,249	4,627	7,600	9,508
Net income available for shareholders	114,709	84,279	204,929	172,836
Preferred Stock Dividends, Income Statement Impact	922	0	2,766	0
Net income available for MAA common shareholders	$ 113,787	$ 84,279	$ 202,163	$ 172,836
Earnings per common share - basic:
Net income available for common shareholders	$ 1	$ 1.12	$ 1.78	$ 2.29
Earnings per common share - diluted:
Net income available for common shareholders	1	1.12	1.78	2.29
Dividends declared per common share	$ 0.87	$ 0.82	2.61	2.46
Distribution Made to Limited Partner, Distributions Declared, Per Unit			$ 2.61	$ 2.46

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Limited Partner [Member]
Consolidated net income	$ 118,958	$ 88,906	$ 212,529	$ 182,344
Unrealized loss from the effective portion of derivitave insturments	90	1,179	(1,252)	(3,840)
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, Net of Tax	(33)	1,042	884	3,359
Comprehensive income attributable to Mid-America Apartments, L.P.	119,015	91,127	212,161	181,863
Parent Company [Member]
Consolidated net income	118,958	88,906	212,529	182,344
Unrealized loss from the effective portion of derivitave insturments	90	1,179	(1,252)	(3,840)
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, Net of Tax	(33)	1,042	884	3,359
Total comprehensive income	119,015	91,127	212,161	181,863
Less: comprehensive income attributable to noncontrolling interests	(4,251)	(4,743)	(7,586)	(9,483)
Comprehensive income attributable to MAA	$ 114,764	$ 86,384	$ 204,575	$ 172,380

Condensed Consolidated Stateme7

Condensed Consolidated Statements of Cash Flows - USD ($)	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Parent Company [Member]
Cash flows from operating activities:
Consolidated net income	$ 212,529,000	$ 182,344,000
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation, Amortization and Accretion, Net	(292,000)	(130,000)
Depreciation and amortization	(374,947,000)	(228,073,000)
Stock compensation expense	8,431,000	5,977,000
Redeemable stock issued	489,000	412,000
Amortization of debt premium	(8,035,000)	(7,546,000)
(Gain) loss from investments in real estate joint ventures	(1,021,000)	(27,000)
Loss on debt extinguishment	(4,753,000)	0
Derivative interest (credit) expense	(9,298,000)	(1,883,000)
Gain on sale of non-depreciable real estate assets	(42,000)	(2,170,000)
Gain on sale of depreciable real estate assets excluded from discontinued operations	(59,045,000)	(48,572,000)
Net casualty loss and other settlement proceeds	(233,000)	(738,000)
Settlement of Forward Swaps	(1,547,000)	0
Changes in assets and liabilities:
Restricted cash	(2,580,000)	(4,955,000)
Other assets	(6,264,000)	(501,000)
Accounts payable	(5,305,000)	(3,158,000)
Accrued expenses and other	44,353,000	35,183,000
Security deposits	164,000	597,000
Net cash provided by operating activities	553,108,000	389,222,000
Cash flows from investing activities:
Net (decrease) increase in cash and cash equivalents	14,315,000	(9,742,000)
Purchases of real estate and other assets	(63,774,000)	(262,268,000)
Normal capital improvements	(82,030,000)	(65,351,000)
Construction capital and other improvements	(7,171,000)	(5,569,000)
Renovations to existing real estate assets	(36,692,000)	(29,554,000)
Development	(142,530,000)	(42,611,000)
Distributions from real estate joint ventures	0	1,823,000
Contributions to Real Estate Joint Ventures	(750,000)	0
Proceeds from disposition of real estate assets	90,040,000	187,425,000
(Funding) return of escrow for future acquisitions	10,591,000	0
Net cash (used in) provided by investing activities	(232,316,000)	(216,105,000)
Cash flows from financing activities:
Net change in credit lines	(240,000,000)	130,000,000
Proceeds from notes payable	597,480,000	0
Principal payments on notes payable	(345,053,000)	(114,753,000)
Payment of deferred financing costs	(5,355,000)	(141,000)
Repurchase of common stock	(4,782,000)	(1,811,000)
Proceeds from issuances of common shares	1,007,000	(216,000)
Proceeds from Stock Options Exercised	432,000	0
Distributions to noncontrolling interests	(10,999,000)	(10,234,000)
Dividends paid on common shares	(296,441,000)	(185,704,000)
Dividends, Preferred Stock, Cash	(2,766,000)	0
Net cash used in financing activities	(306,477,000)	(182,859,000)
Cash and cash equivalents, beginning of period	33,536,000	37,559,000
Cash and cash equivalents, end of period	47,851,000	27,817,000
Supplemental disclosure of cash flow information:
Interest paid	123,735,000	96,271,000
Income Taxes Paid	2,256,000	1,571,000
Supplemental disclosure of noncash investing and financing activities:
Conversion of units to shares of common stock	1,133,000	780,000
Accrued construction in progress	15,787,000	8,742,000
Interest capitalized	5,884,000	1,095,000
Marked To Market Adjustment On Derivative Instruments	12,035,000	1,402,000
Limited Partner [Member]
Cash flows from operating activities:
Consolidated net income	212,529,000	182,344,000
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation, Amortization and Accretion, Net	(292,000)	(130,000)
Depreciation and amortization	(374,947,000)	(228,073,000)
Stock compensation expense	8,431,000	5,977,000
Redeemable stock issued	489,000	412,000
Amortization of debt premium	(8,035,000)	(7,546,000)
(Gain) loss from investments in real estate joint ventures	(1,021,000)	(27,000)
Loss on debt extinguishment	(4,753,000)	0
Derivative interest (credit) expense	(9,298,000)	(1,883,000)
Gain on sale of non-depreciable real estate assets	(42,000)	(2,170,000)
Gain on sale of depreciable real estate assets excluded from discontinued operations	(59,045,000)	(48,572,000)
Net casualty loss and other settlement proceeds	(233,000)	(738,000)
Settlement of Forward Swaps	(1,547,000)	0
Changes in assets and liabilities:
Restricted cash	(2,580,000)	(4,955,000)
Other assets	(6,264,000)	(501,000)
Accounts payable	(5,305,000)	(3,158,000)
Accrued expenses and other	44,353,000	35,183,000
Security deposits	164,000	597,000
Net cash provided by operating activities	553,108,000	389,222,000
Cash flows from investing activities:
Net (decrease) increase in cash and cash equivalents	14,315,000	(9,742,000)
Purchases of real estate and other assets	(63,774,000)	(262,268,000)
Normal capital improvements	(82,030,000)	(65,351,000)
Construction capital and other improvements	(7,171,000)	(5,569,000)
Renovations to existing real estate assets	(36,692,000)	(29,554,000)
Development	(142,530,000)	(42,611,000)
Distributions from real estate joint ventures	0	1,823,000
Contributions to Real Estate Joint Ventures	(750,000)	0
Proceeds from disposition of real estate assets	90,040,000	187,425,000
(Funding) return of escrow for future acquisitions	10,591,000	0
Net cash (used in) provided by investing activities	(232,316,000)	(216,105,000)
Cash flows from financing activities:
Net change in credit lines	(240,000,000)	130,000,000
Proceeds from notes payable	597,480,000	0
Principal payments on notes payable	(345,053,000)	(114,753,000)
Payment of deferred financing costs	(5,355,000)	(141,000)
Repurchase of common units	(4,782,000)	(1,811,000)
Proceeds from issuances of common units	1,007,000	(216,000)
Proceeds from Stock Options Exercised	432,000	0
Distributions paid on common units	(307,440,000)	(195,938,000)
Dividends, Preferred Stock, Cash	(2,766,000)	0
Net cash used in financing activities	(306,477,000)	(182,859,000)
Cash and cash equivalents, beginning of period	33,536,000	37,559,000
Cash and cash equivalents, end of period	47,851,000	27,817,000
Supplemental disclosure of cash flow information:
Interest paid	123,735,000	96,271,000
Income Taxes Paid	2,256,000	1,571,000
Supplemental disclosure of noncash investing and financing activities:
Accrued construction in progress	15,787,000	8,742,000
Interest capitalized	5,884,000	1,095,000
Marked To Market Adjustment On Derivative Instruments	$ 12,035,000	$ 1,402,000

Basis of Presentation and Princ

Basis of Presentation and Principles of Consolidation and Significant Accounting Policies	9 Months Ended
	Sep. 30, 2017
Consolidation and Basis of Presentation and Significant Accounting Policies [Abstract]
Consolidation and Basis of Presentation and Significant Accounting Policies	Basis of Presentation and Principles of Consolidation and Significant Accounting Policies Unless the context otherwise requires, all references to "we," "us," "our," or the "Company" refer collectively to Mid-America Apartment Communities, Inc., together with its consolidated subsidiaries, including Mid-America Apartments, L.P. Unless the context otherwise requires, all references to "MAA" refer only to Mid-America Apartment Communities, Inc. and not any of its consolidated subsidiaries. Unless the context otherwise requires, all references to the "Operating Partnership" or "MAALP" refer to Mid-America Apartments, L.P., together with its consolidated subsidiaries. "Common stock" refers to the common stock of MAA and "shareholders" means the holders of shares of MAA’s common stock. The common units of limited partnership interests in the Operating Partnership are referred to as "OP Units," and the holders of the OP Units are referred to as "common unitholders". As of September 30, 2017 , MAA owned 113,627,014 OP Units (or 96.4% of the total number of OP Units). MAA conducts substantially all of its business and holds substantially all of its assets through the Operating Partnership, and by virtue of its ownership of the OP Units and being the Operating Partnership's sole general partner, MAA has the ability to control all of the day-to-day operations of the Operating Partnership. We believe combining the notes to the condensed consolidated financial statements of MAA and MAALP results in the following benefits: • enhances a readers' understanding of MAA and the Operating Partnership by enabling the reader to view the business as a whole in the same manner that management views and operates the business; • eliminates duplicative disclosure and provides a more streamlined and readable presentation since a substantial portion of the disclosure applies to both MAA and the Operating Partnership; and • creates time and cost efficiencies through the preparation of one combined report instead of two separate reports Management operates MAA and the Operating Partnership as one business. The management of the Company is comprised of individuals who are officers of MAA and employees of the Operating Partnership. We believe it is important to understand the few differences between MAA and the Operating Partnership in the context of how MAA and the Operating Partnership operate as a consolidated company. MAA and the Operating Partnership are structured as an "umbrella partnership REIT," or UPREIT. MAA's interest in the Operating Partnership entitles MAA to share in cash distributions from, and in the profits and losses of, the Operating Partnership in proportion to MAA's percentage interest therein, and entitles MAA to vote on substantially all matters requiring a vote of the partners. MAA's only material asset is its ownership of limited partner interests in the Operating Partnership; therefore, MAA does not conduct business itself, other than acting as the sole general partner of the Operating Partnership, issuing public equity from time to time, and guaranteeing certain debt of the Operating Partnership. The Operating Partnership holds, directly or indirectly, all of our real estate assets. Except for net proceeds from public equity issuances by MAA, which are contributed to the Operating Partnership in exchange for OP Units, the Operating Partnership generates the capital required by our business through the Operating Partnership's operations, direct or indirect incurrence of indebtedness, and issuance of OP units. The presentation of MAA's shareholders' equity and the Operating Partnership's capital is the principal area of difference between the condensed consolidated financial statements of MAA and those of the Operating Partnership. MAA's shareholders' equity may include shares of preferred stock, shares of common stock, additional paid-in capital, cumulative earnings, cumulative distributions, noncontrolling interests, preferred units, treasury shares, accumulated other comprehensive income and redeemable common units. The Operating Partnership's capital may include common capital and preferred capital of the general partner (MAA), limited partners' preferred capital, limited partners' noncontrolling interests, accumulated other comprehensive income and redeemable common units. Redeemable common units represent the number of outstanding OP Units as of the date of the applicable balance sheet, valued at the greater of the closing market price of MAA's common stock or the aggregate value of the individual partners' capital balances. Holders of OP Units (other than MAA and its corporate affiliates) may require the Operating Partnership to redeem their OP Units from time to time, in which case the Operating Partnership may, at its option, pay the redemption price either in cash (in an amount per OP Unit equal, in general, to the average closing price of MAA's common stock on the NYSE over a specified period prior to the redemption date) or by delivering one share of MAA's common stock (subject to adjustment under specified circumstances) for each OP Unit so redeemed. Organization of Mid-America Apartment Communities, Inc. On December 1, 2016, MAA completed a merger with Post Properties, Inc., or Post Properties. Pursuant to the Agreement and Plan of Merger, or the Merger Agreement, Post Properties merged with and into MAA, with MAA continuing as the surviving corporation, or the Parent Merger, and Post Apartment Homes, L.P, or Post LP, merged with and into MAALP, with MAALP continuing as the surviving entity, or the Partnership Merger. We refer to the Parent Merger, together with the Partnership Merger, as the Merger in this Report. Under the terms of the Merger Agreement, each share of Post Properties common stock was converted into the right to receive 0.71 of a newly issued share of MAA common stock, including the right, if any, to receive cash in lieu of fractional shares of MAA common stock. In addition, each limited partner interest in Post LP designated as a "Class A Unit" automatically converted into the right to receive 0.71 of a newly issued partnership unit of MAALP. Also, each share of Post Properties' 8 1/2% Series A Cumulative Redeemable Preferred Stock, which we refer to as the Post Properties Series A preferred stock, was automatically converted into the right to receive one newly issued share of MAA's 8.50% Series I Cumulative Redeemable Preferred Stock, $0.01 par value per share, which we refer to as MAA Series I preferred stock. Each newly issued share of MAA Series I preferred stock has substantially the same rights, preferences, privileges, and voting powers as those of the Post Properties Series A preferred stock. As of September 30, 2017 , we owned and operated 302 apartment communities, comprising 99,612 apartment units located in 17 states, through the Operating Partnership. As of September 30, 2017 , we also owned a 35.0% interest in an unconsolidated real estate joint venture and a 32.0% interest in an unconsolidated limited partnership. As of September 30, 2017 , we had five development communities under construction totaling 1,434 apartment units. Total expected costs for the development projects are $305.0 million , of which $235.3 million has been incurred through September 30, 2017 . We expect to complete construction on two projects by the fourth quarter of 2017, one project by the first quarter of 2018, one project by the third quarter of 2018, and one project by the fourth quarter of 2018. Twenty-nine of our multifamily properties include retail components with approximately 600,000 square feet of gross leasable area. We also have four wholly-owned commercial properties, which we acquired through the Merger, with approximately 232,000 square feet of combined gross leasable area. Basis of Presentation and Principles of Consolidation The accompanying Condensed Consolidated Financial Statements have been prepared by our management in accordance with United States generally accepted accounting principles, or GAAP, and applicable rules and regulations of the Securities and Exchange Commission, or the SEC. The Condensed Consolidated Financial Statements of MAA presented herein include the accounts of MAA, the Operating Partnership, and all other subsidiaries in which MAA has a controlling financial interest. MAA owns approximately 92.5% to 100% of all consolidated subsidiaries, including the Operating Partnership. The Condensed Consolidated Financial Statements of MAALP presented herein include the accounts of MAALP and all other subsidiaries in which MAALP has a controlling financial interest. MAALP owns, directly or indirectly, 92.5% to 100% of all consolidated subsidiaries. In our opinion, all adjustments necessary for a fair presentation of the Condensed Consolidated Financial Statements have been included, and all such adjustments were of a normal recurring nature. All significant intercompany accounts and transactions have been eliminated in consolidation. We invest in entities which may qualify as variable interest entities, or VIEs, and MAALP is considered a VIE. A VIE is a legal entity in which the equity investors lack sufficient equity at risk for the entity to finance its activities without additional subordinated financial support or, as a group, the holders of the equity investment at risk lack the power to direct the activities of a legal entity as well as the obligation to absorb its expected losses or the right to receive its expected residual returns. MAALP is classified as a VIE, since the limited partners lack substantive kick-out rights and substantive participating rights. We consolidate all VIEs for which we are the primary beneficiary and use the equity method to account for investments that qualify as VIEs but for which we are not the primary beneficiary. In determining whether we are the primary beneficiary of a VIE, we consider qualitative and quantitative factors, including but not limited to, those activities that most significantly impact the VIE's economic performance and which party controls such activities. We use the equity method of accounting for our investments in entities for which we exercise significant influence, but do not have the ability to exercise control. The factors considered in determining that we do not have the ability to exercise control include ownership of voting interests and participatory rights of investors (see "Investment in Unconsolidated Real Estate Joint Ventures" below). Noncontrolling Interests At September 30, 2017 , the Company had two types of noncontrolling interests, (1) noncontrolling interests related to the common unitholders of the Operating Partnership (see Note 11) and (2) noncontrolling interests related to its consolidated real estate entities (see "Investment in Consolidated Real Estate Joint Ventures" below). Investment in Unconsolidated Joint Ventures Immediately prior to the effective date of the Merger, Post Properties together with other institutional investors, in a limited liability company, or the Apartment LLC, owned one apartment community, Post Massachusetts Avenue, located in Washington, D.C. Post Properties had a 35.0% equity interest in this unconsolidated joint venture, which we retained immediately following the effectiveness of the Merger and as of September 30, 2017 . We provide property and asset management services to the Apartment LLC for which we earn fees. This joint venture was determined to be a VIE, but we are not designated as a primary beneficiary. As a result, we account for our investment in the Apartment LLC using the equity method of accounting, as we are able to exert significant influence, but do not have a controlling interest in this joint venture. At September 30, 2017 , our investment in the Apartment LLC totaled $45.1 million . During September 2017, MAA entered into a limited partnership together with a general partner and other limited partners to form Real Estate Technology Ventures, L.P. MAA's equity interest in the partnership is 32.0% , which is considered more than minor. This joint venture was determined to be a VIE, but we are not designated as a primary beneficiary. Therefore, we account for our investment in the limited partnership using the equity method of accounting, as we are able to exert significant influence over the partnership but do not have a controlling interest in this joint venture. At September 30, 2017 , our investment in the limited partnership totaled $0.8 million , and we are committed to make additional capital contributions totaling $14.2 million over the next five years from the date of the initial capital contribution. Investment in Consolidated Real Estate Joint Ventures In 2015, Post Properties entered into a joint venture arrangement with a private real estate company to develop, construct and operate a 358 -unit apartment community in Denver, Colorado. At September 30, 2017 , we owned a 92.5% equity interest in the consolidated joint venture. In 2015, this joint venture acquired the land site and initiated the development of the apartment community. The venture partner will generally be responsible for the development and construction of the community and we will continue to manage the community upon its completion. This joint venture was determined to be a VIE with us designated as the primary beneficiary. As a result, the accounts of the joint venture are consolidated by us. At September 30, 2017 , our consolidated assets, liabilities and equity included construction in progress of $60.3 million , land of $14.5 million , and accounts payable and accrued expenses of $6.2 million . Assets Held for Sale During September 2017, one land parcel was classified as held for sale. The criteria for classifying the land parcel as held for sale were met during June; however, the sale is not expected to close until the fourth quarter of 2017. As a result, the assets and liabilities associated with the land parcel were presented as held for sale in the Condensed Consolidated Balance Sheets.

Business Combinations

Business Combinations	9 Months Ended
	Sep. 30, 2017
Business Combinations - Additional Information [Abstract]
Business Combination Disclosure [Text Block]	Business Combination On December 1, 2016, we completed the Merger. As part of the Merger, we acquired 61 wholly-owned apartment communities comprising 24,138 apartment units, including 269 apartment units in one community held in an unconsolidated entity, and 2,262 apartment units in six communities that were under development at the Merger date. Post Properties had operations in ten markets across the United States. In addition to the apartment communities, we also acquired four commercial properties, totaling approximately 232,000 square feet of combined gross leasable area. The consolidated net assets and results of operations of Post Properties are included in our Consolidated Financial Statements from the closing date, December 1, 2016, going forward. The total purchase price of approximately $4.0 billion was determined based on the number of shares of Post Properties' common stock, the number of shares of Post Properties’ Series A preferred stock, and shares of Post LP's Class A Units of limited partnership interest outstanding as of December 1, 2016, in addition to cash consideration provided by the Operating Partnership immediately prior to the Merger to pay off a $300.0 million Post LP unsecured term loan and a $162.0 million Post LP line of credit, both outstanding from Wells Fargo. In all cases in which MAA’s common stock price was a determining factor in arriving at final consideration for the Merger, the stock price used to determine the purchase price was the opening price of MAA’s common stock on December 1, 2016 ( $91.41 per share). At the date of acquisition, the MAA Series I preferred stock consideration was valued at $ 77.00 per share, which included a $ 14.24 per share bifurcated call option (See Notes 8 & 9). The total purchase price also included $2.0 million of other consideration, a majority of which related to assumed stock compensation plans. As a result of the Merger, we issued approximately 38.0 million shares of MAA common stock, approximately 80,000 OP Units, and 867,846 newly issued shares of MAA Series I preferred stock. The Merger has been accounted for using the acquisition method of accounting in accordance with Accounting Standards Codification, or ASC, 805, Business Combinations , which requires, among other things, that the assets acquired and liabilities assumed be recognized at their acquisition date fair values. For larger, portfolio style acquisitions, like the Merger, management engages a third party valuation specialist to assist with the fair value assessment, which includes an allocation of the purchase price. Similar to management's methods, the third party uses cash flow analysis as well as an income approach and a market approach to determine the fair value of assets acquired. The third party uses stabilized net operating income, or NOI, and market specific capitalization and discount rates. Management reviews the inputs used by the third party specialist as well as the allocation of the purchase price provided by the third party to ensure reasonableness and that the procedures are performed in accordance with management's policy. The allocation of the purchase price is based on management’s assessment, which may differ as more information becomes available. Subsequent adjustments made to the purchase price allocation, if any, are made within the allocation period, which typically does not exceed one year. The allocation of the purchase price described above requires a significant amount of judgment and represents management's best estimate of the fair value as of the acquisition date. The following preliminary purchase price allocation for the Merger reflects updates primarily to an adjustment to litigation reserves offset by increased derivative asset values on the preferred share bifurcated call option (included in "Other assets") and real estate asset values from our December 31, 2016 estimates. Such preliminary purchase price allocation was based on our valuation as well as estimates and assumptions of the acquisition date fair value of the tangible and intangible assets acquired and liabilities assumed. The purchase price was allocated as follows (in thousands): Land $ 875,294 Buildings and improvements 3,397,342 Furniture, fixtures and equipment 81,243 Development and capital improvements in progress 183,881 Undeveloped land 24,200 Commercial properties, net 3,610 Investment in real estate joint venture 44,435 Lease intangible assets 53,192 Cash and cash equivalents 34,292 Restricted cash 3,608 Deferred costs and other assets, excluding lease intangible assets 41,803 Total assets acquired 4,742,900 Notes payable (595,609) Fair market value of interest rate swaps (2,118) Lease intangible liabilities (1,661) Accounts payable, accrued expenses, and other liabilities (132,613) Total liabilities assumed, including debt (732,001 ) Noncontrolling interests - consolidated real estate entity (2,306 ) Total purchase price $ 4,008,593 The purchase price accounting reflected in the accompanying financial statements is based upon estimates and assumptions that are subject to change within the measurement period, pursuant to ASC 805. See Note 12 for loss contingencies identified, measured, and included in "Accounts payable, accrued expenses, and other liabilities" in the allocation above. We have preliminarily completed our valuation procedures. Adjustments may still occur as the valuation and revised preliminary purchase allocation is finalized in areas such as real estate related assets and liabilities, equity investments, litigation reserves, debt and debt related instruments, and certain other acquired assets and liabilities assumed. We will complete our purchase price allocation during the fourth quarter of 2017. We incurred Merger and integration related expenses of $14.5 million for the nine months ended September 30, 2017 . These amounts were expensed as incurred and are included in the Condensed Consolidated Statements of Operations in the items titled "Merger related expenses", primarily consisting of severance and professional costs, and "Integration related expenses", primarily consisting of temporary systems, staffing, and facilities costs.

Earnings Per Common Share of MA

Earnings Per Common Share of MAA	9 Months Ended
	Sep. 30, 2017
Earnings Per Common Share of MAA [Abstract]
Earnings Per Share [Text Block]	Earnings per Common Share of MAA Basic earnings per share is computed by dividing net income available for MAA common shareholders by the weighted average number of shares outstanding during the period. All outstanding unvested restricted share awards contain rights to non-forfeitable dividends and participate in undistributed earnings with common shareholders and, accordingly, are considered participating securities that are included in the two-class method of computing basic earnings per share. Both the unvested restricted shares and other potentially dilutive common shares, and the related impact to earnings, are considered when calculating earnings per share on a diluted basis with our diluted earnings per share being the more dilutive of the treasury stock or two-class methods. OP Units are included in dilutive earnings per share calculations when they are dilutive to earnings per share. For the three and nine months ended September 30, 2017 and 2016 , MAA's basic earnings per share was computed using the two-class method, and MAA's diluted earnings per share was computed using the more dilutive of the treasury stock method or two-class method, as presented below: (dollars and shares in thousands, except per share amounts) Three months ended September 30, Nine months ended September 30, 2017 2016 2017 2016 Shares Outstanding Weighted average common shares - basic 113,434 75,302 113,392 75,276 Weighted average partnership units outstanding — (1) — (1) — (1) 4,156 Effect of dilutive securities 219 — (2) 270 246 Weighted average common shares - diluted 113,653 75,302 113,662 79,678 Calculation of Earnings per Share - basic Net income $ 118,958 $ 88,906 $ 212,529 $ 182,344 Net income attributable to noncontrolling interests (4,249 ) (4,627 ) (7,600 ) (9,508 ) Unvested restricted stock (allocation of earnings) (181 ) (254 ) (337 ) (485 ) Preferred dividends (922 ) — (2,766 ) — Net income available for common shareholders, adjusted $ 113,606 $ 84,025 $ 201,826 $ 172,351 Weighted average common shares - basic 113,434 75,302 113,392 75,276 Earnings per share - basic $ 1.00 $ 1.12 $ 1.78 $ 2.29 Calculation of Earnings per Share - diluted Net income $ 118,958 $ 88,906 $ 212,529 $ 182,344 Net income attributable to noncontrolling interests (4,249 ) (1) (4,628 ) (1) (7,600 ) (1) — Unvested restricted stock (allocation of earnings) — (254 ) (2) — — Preferred dividends (922 ) — (2,766 ) — Net income available for common shareholders, adjusted $ 113,787 $ 84,024 $ 202,163 $ 182,344 Weighted average common shares - diluted 113,653 75,302 113,662 79,678 Earnings per share - diluted $ 1.00 $ 1.12 $ 1.78 $ 2.29 (1) For both the three and nine months ended September 30, 2017 and the three months ended September 30, 2016 , 4.2 million OP Units and their related income are not included in the diluted earnings per share calculations as they are not dilutive. (2) For the three months ended September 30, 2016 , 0.2 million potentially dilutive securities and their related income are not included in the diluted earnings per share calculations as they are not dilutive.

Earnings Per OP Unit of MAALP

Earnings Per OP Unit of MAALP	9 Months Ended
	Sep. 30, 2017
Earnings Per OP Unit of MAALP [Abstract]
Earnings Per Unit [Text Block]	Earnings per OP Unit of MAALP Basic earnings per OP Unit is computed by dividing net income available for common unitholders by the weighted average number of OP Units outstanding during the period. All outstanding unvested restricted unit awards contain rights to non-forfeitable distributions and participate in undistributed earnings with common unitholders and, accordingly, are considered participating securities that are included in the two-class method of computing basic earnings per OP unit. Diluted earnings per OP Unit reflects the potential dilution that could occur if securities or other contracts to issue OP Units were exercised or converted into OP Units. A reconciliation of the numerators and denominators of the basic and diluted earnings per OP Unit computations for the three and nine months ended September 30, 2017 and 2016 is presented below: (dollars and units in thousands, except per unit amounts) Three months ended September 30, Nine months ended September 30, 2017 2016 2017 2016 Units Outstanding Weighted average common units - basic 117,643 79,449 117,607 79,432 Effect of dilutive securities 219 — (1) 270 246 Weighted average common units - diluted 117,862 79,449 117,877 79,678 Calculation of Earnings per Unit - basic Net income $ 118,958 $ 88,906 $ 212,529 $ 182,344 Unvested restricted stock (allocation of earnings) (181 ) (254 ) (337 ) (484 ) Preferred unit distributions (922 ) — (2,766 ) — Net income available for common unitholders, adjusted $ 117,855 $ 88,652 $ 209,426 $ 181,860 Weighted average common units - basic 117,643 79,449 117,607 79,432 Earnings per common unit - basic $ 1.00 $ 1.12 $ 1.78 $ 2.29 Calculation of Earnings per Unit - diluted Net income $ 118,958 $ 88,906 $ 212,529 $ 182,344 Unvested restricted stock (allocation of earnings) — (254 ) (1) — — Preferred unit distributions (922 ) — (2,766 ) — Net income available for common unitholders, adjusted $ 118,036 $ 88,652 $ 209,763 $ 182,344 Weighted average common units - diluted 117,862 79,449 117,877 79,678 Earnings per common unit - diluted $ 1.00 $ 1.12 $ 1.78 $ 2.29 (1) For the three months ended September 30, 2016 , 0.2 million potentially dilutive securities and their related income are not included in the diluted earnings per share calculations as they are not dilutive.

MAA Equity

MAA Equity	9 Months Ended
	Sep. 30, 2017
MAA Equity [Abstract]
Consolidated Statements of Equity [Text Block]	MAA Equity Changes in total equity and its components for the nine-month periods ended September 30, 2017 and 2016 were as follows (dollars in thousands, except per share and per unit data): Mid-America Apartment Communities, Inc. Shareholders' Equity Preferred Stock Amount Common Stock Amount Additional Paid-In Capital Accumulated Distributions in Excess of Net Income Accumulated Other Comprehensive Income (Loss) Noncontrolling Interest Operating Partnership Noncontrolling Interest - Consolidated Real Estate Entity Total Equity EQUITY BALANCE DECEMBER 31, 2016 $ 9 $ 1,133 $ 7,109,012 $ (707,479 ) $ 1,144 $ 235,976 $ 2,306 $ 6,642,101 Net income attributable to controlling interest — — — 204,929 — 7,600 — 212,529 Other comprehensive income - derivative instruments (cash flow hedges) — — — — (354 ) (14 ) — (368 ) Issuance and registration of common shares — 1 153 — — — — 154 Issuance and registration of preferred shares — — 2,007 — — — — 2,007 Shares repurchased and retired — — (4,782 ) — — — — (4,782 ) Exercise of stock options — — 218 — — — — 218 Shares issued in exchange for common units — — 1,133 — — (1,133 ) — — Shares issued in exchange for redeemable stock — — 1,482 — — — — 1,482 Redeemable stock fair market value adjustment — — — (870 ) — — — (870 ) Adjustment for noncontrolling interest ownership in operating partnership — — 54 — — (54 ) — — Amortization of unearned compensation — — 8,552 (114 ) — — — 8,438 Dividends on preferred stock — — — (2,766 ) — — — (2,766 ) Dividends on common stock ($2.61 per share) — — — (296,535 ) — — — (296,535 ) Dividends on noncontrolling interest units ($2.61 per unit) — — — — — (10,982 ) — (10,982 ) EQUITY BALANCE SEPTEMBER 30, 2017 $ 9 $ 1,134 $ 7,117,829 $ (802,835 ) $ 790 $ 231,393 $ 2,306 $ 6,550,626 Mid-America Apartment Communities, Inc. Shareholders' Equity Preferred Stock Amount Common Stock Amount Additional Paid-In Capital Accumulated Distributions in Excess of Net Income Accumulated Other Comprehensive Income (Loss) Noncontrolling Noncontrolling Interest - Consolidated Real Estate Entity Total Equity EQUITY BALANCE DECEMBER 31, 2015 $ — $ 753 $ 3,627,074 $ (634,141 ) $ (1,589 ) $ 165,726 $ — $ 3,157,823 Net income attributable to controlling interest — — — 172,836 — 9,508 — 182,344 Other comprehensive loss - derivative instruments (cash flow hedges) — — — — (456 ) (25 ) — (481 ) Issuance and registration of common shares — 1 (739 ) — — — — (738 ) Shares repurchased and retired — — (1,811 ) — — — — (1,811 ) Shares issued in exchange for common units — — 780 — — (780 ) — — Shares issued in exchange for redeemable stock — — 122 — — — — 122 Redeemable stock fair market value adjustment — — — (296 ) — — — (296 ) Adjustment for noncontrolling interest ownership in operating partnership — — (38 ) — — 38 — — Amortization of unearned compensation — — 6,625 — — — — 6,625 Dividends on common stock ($2.46 per share) — — — (185,789 ) — — — (185,789 ) Dividends on noncontrolling interest units ($2.46 per unit) — — — — — (10,217 ) — (10,217 ) EQUITY BALANCE SEPTEMBER 30, 2016 $ — $ 754 $ 3,632,013 $ (647,390 ) $ (2,045 ) $ 164,250 $ — $ 3,147,582

MAALP Capital

MAALP Capital	9 Months Ended
	Sep. 30, 2017
MAALP Capital [Abstract]
Consolidated Statements of Changes in Capital [Text Block]	MAALP Capital Changes in total capital and its components for the nine-month periods ended September 30, 2017 and 2016 were as follows (dollars in thousands, except per unit data): Mid-America Apartments, L.P. Unitholders' Capital Limited Partner General Partner Preferred Units Accumulated Noncontrolling Interest - Consolidated Real Estate Entity Total Partnership Capital CAPITAL BALANCE DECEMBER 31, 2016 $ 235,976 $ 6,337,721 $ 64,833 $ 1,246 $ 2,306 $ 6,642,082 Net income attributable to controlling interest 7,600 202,163 2,766 — — 212,529 Other comprehensive income - derivative instruments (cash flow hedges) — — — (368 ) — (368 ) Issuance of units — 154 2,007 — — 2,161 Units repurchased and retired — (4,782 ) — — — (4,782 ) Exercise of unit options — 218 — — — 218 General partner units issued in exchange for limited partner units (1,133 ) 1,133 — — — — Units issued in exchange for redeemable units — 1,482 — — — 1,482 Redeemable units fair market value adjustment — (870 ) — — — (870 ) Adjustment for limited partners' capital at redemption value (68 ) 68 — — — — Amortization of unearned compensation — 8,438 — — — 8,438 Distributions to preferred unitholders — — (2,766 ) — — (2,766 ) Distributions ($2.61 per unit) (10,982 ) (296,535 ) — — — (307,517 ) CAPITAL BALANCE SEPTEMBER 30, 2017 $ 231,393 $ 6,249,190 $ 66,840 $ 878 $ 2,306 $ 6,550,607 Mid-America Apartments, L.P. Unitholders' Capital Limited Partner General Partner Preferred Units Accumulated Noncontrolling Interest - Consolidated Real Estate Entity Total Partnership Capital CAPITAL BALANCE DECEMBER 31, 2015 $ 165,726 $ 2,993,696 $ — $ (1,618 ) $ — $ 3,157,804 Net income attributable to controlling interest 9,508 172,836 — — — 182,344 Other comprehensive loss - derivative instruments (cash flow hedges) — — — (481 ) — (481 ) Issuance of units — (738 ) — — — (738 ) Units repurchased and retired — (1,811 ) — — — (1,811 ) General partner units issued in exchange for limited partner units (780 ) 780 — — — — Units issued in exchange for redeemable units — 122 — — — 122 Redeemable units fair market value adjustment — (296 ) — — — (296 ) Adjustment for limited partners' capital at redemption value 13 (13 ) — — — — Amortization of unearned compensation — 6,625 — — — 6,625 Distributions ($2.46 per unit) (10,217 ) (185,789 ) — — — (196,006 ) CAPITAL BALANCE SEPTEMBER 30, 2016 $ 164,250 $ 2,985,412 $ — $ (2,099 ) $ — $ 3,147,563

Borrowings

Borrowings	9 Months Ended
	Sep. 30, 2017
Notes To Financial Statements [Abstract]
Notes Payable	Borrowings The weighted average effective interest rate at September 30, 2017 and December 31, 2016 for the $4.5 billion of debt outstanding was 3.5% at both balance sheet dates. Our debt consists of an unsecured revolving credit facility, unsecured term loans, senior unsecured notes, a secured credit facility with the Federal National Mortgage Association, or the Fannie Mae Facility, and secured property mortgages. We utilize fixed rate borrowings, interest rate swaps, and interest rate caps to manage our current and future interest rate risk. At September 30, 2017 , we had $2.8 billion of senior unsecured notes and unsecured term loans fixed at an average interest rate of 3.8% , $300.0 million of variable rate unsecured term loans with an average interest rate of 2.2% , and a $1.0 billion unsecured variable rate revolving credit facility with an average interest rate of 2.1% with $250.0 million borrowed at September 30, 2017 . Additionally, we had $110.0 million of secured variable rate debt outstanding at an average interest rate of 1.7% and $50.0 million of capped secured variable rate debt at an average interest rate of 1.7% . The interest rate on all other secured debt, totaling $950.0 million , was hedged or fixed at an average interest rate of 4.0% . Unsecured Revolving Credit Facility We maintain a $1.0 billion unsecured credit facility with a syndicate of banks led by KeyBank National Association, or the KeyBank Facility. The KeyBank Facility includes an expansion option up to $1.5 billion . The KeyBank Facility bears an interest rate of The London Interbank Offered Rate, or LIBOR, plus a spread of 0.85% to 1.55% based on an investment grade pricing grid and is currently bearing interest at 2.14% . The KeyBank Facility expires in April 2020 with an option to extend for an additional six months. At September 30, 2017 , we had $250.0 million actually borrowed under this facility, and another approximately $2.5 million of the facility used to support letters of credit. Unsecured Term Loans We also maintain four term loans with a syndicate of banks, one led by KeyBank National Association, or KeyBank, two by Wells Fargo Bank, N.A., or Wells Fargo, and one by U.S. Bank National Association, or U.S. Bank, respectively. The KeyBank term loan has a balance of $150.0 million , matures in 2021, and has a variable interest rate of LIBOR plus a spread of 0.90% to 1.75% based on our credit ratings. The Wells Fargo term loans have balances of $250.0 million and $300.0 million , respectively, mature in 2018 and 2022, respectively, and have variable interest rates of LIBOR plus spreads of 0.90% to 1.90% % and 0.90% to 1.75% %, respectively, based on our credit ratings. The U.S. Bank term loan has a balance of $150.0 million , matures in 2020, and has a variable interest rate of LIBOR plus a spread of 0.90% to 1.90% based on our credit ratings. Senior Unsecured Notes As of September 30, 2017 , we had approximately $2.0 billion (face value) of publicly issued notes and $310 million of private placement notes. These senior unsecured notes had maturities at issuance ranging from five to twelve years , averaging 7.1 years remaining until maturity as of September 30, 2017 . On May 9, 2017, the Operating Partnership publicly issued $600.0 million in aggregate principal amount of notes, maturing on June 1, 2027 with an interest rate of 3.60% per annum, or the 2027 Notes. The purchase price paid by the initial purchasers was 99.58% of the principal amount. The 2027 Notes are general unsecured senior obligations of the Operating Partnership and rank equally in right of payment with all other senior unsecured indebtedness of the Operating Partnership. Interest on the 2027 Notes is payable on June 1 and December 1 of each year, beginning on December 1, 2017. The net proceeds from the offering, after deducting the original issue discount of approximately $2.5 million and underwriting commissions and expenses of approximately $3.9 million, were approximately $593.6 million. The 2027 Notes have been reflected net of discount and debt issuance costs in the Condensed Consolidated Balance Sheet. In connection with the issuance of the 2027 Notes, we cash settled $300.0 million in forward interest rate swap agreements, entered into during the first two quarters in the year to effectively lock the interest rate on the planned transaction, which produced an effective interest rate of 3.68% over the ten year life of the 2027 Notes. On July 17, 2017, we paid off $150.0 million of senior unsecured notes assumed as part of the Merger. The notes were scheduled for maturity in October 2017. Secured Credit Facility We maintain a $160.0 million secured credit facility with Prudential Mortgage Capital, which is credit enhanced by the Fannie Mae Facility. The Fannie Mae Facility has maturities from 2017 through 2018. Borrowings under the Fannie Mae Facility totaled $160.0 million at September 30, 2017 , all of which was variable rate at an average interest rate of 1.7% . The available borrowing capacity at September 30, 2017 was $160.0 million . Secured Property Mortgages At September 30, 2017 , we had $933.3 million of fixed rate conventional property mortgages with an average interest rate of 4.0% and an average maturity in 2019. On February 7, 2017, we paid off a $15.8 million mortgage associated with the Grand Cypress apartment community. The mortgage was scheduled for maturity in August 2017. On May 31, 2017, we paid off a $156.4 million mortgage associated with the following apartment communities: CG at Edgewater, CG at Madison, CG at Seven Oaks, CG at Town Park, CG at Barrett Creek, CG at River Oaks, and CG at Huntersville. The mortgage was scheduled for maturity in June 2019. On September 11, 2017, we paid off a $13.9 million mortgage associated with the Venue at Stonebridge Ranch. The loan was scheduled for maturity in December 2017. In addition to these payoffs, we paid $9.0 million associated with property mortgage principal amortizations during the nine months ended September 30, 2017 . Guarantees MAA fully and unconditionally guarantees the following debt incurred by the Operating Partnership: • $160.0 million of the Fannie Mae Facility, of which $160.0 million has been borrowed as of September 30, 2017 ; and • $310.0 million of the privately placed senior unsecured notes. Total Outstanding Debt The following table summarizes our indebtedness at September 30, 2017 (dollars in thousands): Borrowed Balance Effective Rate Average Contract Maturity Fixed Rate Secured Debt Individual property mortgages $ 933,256 4.0 % 9/11/2019 Variable Rate Secured Debt (1) Fannie Mae Facility 160,000 1.7 % 6/1/2018 Fair market value adjustments and debt issuance costs 16,717 Total Secured Debt 1,109,973 3.6 % 7/3/2019 Unsecured Debt Variable rate revolving credit facility 250,000 2.1 % 4/15/2020 Variable rate term loans 300,000 2.2 % 8/29/2020 Term loans fixed with swaps 550,000 3.0 % 4/17/2018 Fixed rate senior notes 2,310,000 4.0 % 10/24/2024 Fair market value adjustments, debt issuance costs and discounts (27,139 ) Total Unsecured Debt 3,382,861 3.5 % 1/18/2023 Total Outstanding Debt $ 4,492,834 3.5 % 2/13/2022 (1) Includes capped balances.

Derivatives and Hedging Activit

Derivatives and Hedging Activities	9 Months Ended
	Sep. 30, 2017
Notes To Financial Statements [Abstract]
Derivatives and Hedging Activities	Derivatives and Hedging Activities Risk Management Objective of Using Derivatives We are exposed to certain risks arising from both our business operations and economic conditions. We principally manage our exposures to a wide variety of business and operational risks through management of our core business activities. We manage economic risks, including interest rate, liquidity and credit risk, primarily by managing the amount, sources and duration of our debt funding and the use of derivative financial instruments. Specifically, we enter into derivative financial instruments to manage exposures that arise from business activities that result in the payment of future contractual and forecasted cash amounts, principally related to our borrowings, the value of which are determined by changing interest rates, related cash flows and other factors. Cash Flow Hedges of Interest Rate Risk Our objectives in using interest rate derivatives are to add stability to interest expense and to manage our exposure to interest rate movements. To accomplish these objectives, we use interest rate swaps and interest rate caps as part of our interest rate risk management strategy. Interest rate swaps designated as cash flow hedges involve the receipt of variable amounts from a counterparty in exchange for us making fixed-rate payments over the life of the agreements without exchange of the underlying notional amount. Interest rate caps designated as cash flow hedges involve the receipt of variable amounts from a counterparty if interest rates rise above the strike rate on the contract in exchange for an up-front premium. The effective portion of changes in the fair value of derivatives designated and that qualify as cash flow hedges is recorded in accumulated other comprehensive income and is subsequently reclassified into earnings in the period that the hedged forecasted transaction affects earnings. During the three and nine months ended September 30, 2017 and 2016 , such derivatives were used to hedge the variable cash flows associated with existing variable-rate debt and forecasted issuances of fixed-rate debt. The ineffective portion of the change in fair value of the derivatives is recognized directly in earnings and is mainly attributable to a mismatch in the underlying indices of the derivatives and the hedged interest payments made on our variable-rate debt and due to the designation of acquired interest rate swaps with a non-zero fair value at inception. Amounts reported in "Accumulated other comprehensive income" related to derivatives designated as qualifying cash flow hedges will be reclassified to interest expense as interest payments are made on our variable-rate or fixed-rate debt. During the next twelve months, we estimate that an additional $80,500 will be reclassified to earnings as an increase to Interest expense, which primarily represents the difference between our fixed interest rate swap payments and the projected variable interest rate swap receipts. As of September 30, 2017 , we had the following outstanding interest rate derivatives that were designated as cash flow hedges of interest rate risk: Interest Rate Derivative Number of Instruments Notional Amount Interest Rate Caps 2 $ 50,000,000 Interest Rate Swaps 10 $ 550,000,000 The fair value of our interest rate derivatives designated as hedging instruments at September 30, 2017 included $2.0 million of asset derivatives reported in Other assets and $2.6 million of liability derivatives reported in the Fair market value of interest rate swaps in the Condensed Consolidated Balance Sheet. The fair value of our interest rate derivatives designated as hedging instruments at December 31, 2016 included $2.4 million of asset derivatives reported in "Other assets" and $7.6 million of liability derivatives reported in "Fair market value of interest rate swaps" in the Condensed Consolidated Balance Sheet. Bifurcated Embedded Derivatives Additionally, as a result of the Merger (see Note 2), on December 1, 2016, we issued 867,846 shares of MAA Series I preferred stock as consideration. These shares are redeemable, at our option, on and after October 1, 2026, at the redemption price per share of $50 (see Note 10). This redemption feature embedded in the MAA Series I preferred stock was evaluated in accordance with ASC 815, Derivatives and Hedging , and we determined that we were required to bifurcate the value associated with this feature from its host instrument, the perpetual preferred shares, and account for it as a freestanding derivative on the balance sheet at fair value as a result of the call option. Thus, the redemption feature embedded in the MAA Series I preferred stock is reported as a derivative asset in "Other assets" on the accompanying Condensed Consolidated Balance Sheets and is adjusted to its fair value at each reporting date, with a corresponding non-cash adjustment to Other non-property income or expense. The embedded derivative for these preferred shares was initially recorded at a fair value of $10.8 million at the date of the Merger and as of December 31, 2016 and then subsequently adjusted to fair value of $18.2 million at September 30, 2017 . This $7.4 million year-to-date increase includes a purchase price allocation adjustment of $1.6 million related to the Merger opening balance sheet date, which was recorded in the first quarter of 2017 , as well as $5.8 million of year-to-date mark to market adjustments of non-cash income recorded to reflect the change in fair value of the derivative asset in the nine months ended September 30, 2017 . Tabular Disclosure of the Effect of Derivative Instruments on the Condensed Consolidated Statements of Operations The table below presents the effect of our derivative financial instruments on the Condensed Consolidated Statements of Operations for the three and nine months ended September 30, 2017 and 2016 (dollars in thousands): Derivatives in Cash Flow Hedging Relationships Amount of Gain or (Loss) Location of Gain or Amount of Gain or (Loss) Location of Gain or Amount of Gain or (Loss) Recognized in Interest Expense (Ineffective Three months ended September 30, 2017 2016 2017 2016 2017 2016 Interest rate contracts $ 90 $ 1,179 Interest Expense $ 33 $ (1,042 ) Interest Expense $ (3 ) $ 96 Nine months ended September 30, Interest rate contracts $ (1,252 ) $ (3,840 ) Interest Expense $ (884 ) $ (3,359 ) Interest Expense $ (17 ) $ (67 ) Derivatives Not Designated as Hedging Instruments Location of Gain Recognized in Income on Derivative Amount of Gain Recognized in Income on Derivative Three months ended September 30, 2017 2016 Preferred stock embedded derivative Interest and other non-property income $ 4,107 $ — Nine months ended September 30, Preferred stock embedded derivative Interest and other non-property income $ 5,827 $ — Credit-Risk-Related Contingent Features As of September 30, 2017 , derivatives that were in a net liability position and subject to credit-risk-related contingent features had a termination value of $2.8 million , which included accrued interest but excluded any adjustment for nonperformance risk. These derivatives had a fair value, gross of asset positions, of $2.6 million at September 30, 2017 . Certain of our derivative contracts contain a provision where we could be declared in default on our derivative obligations if repayment of the underlying indebtedness is accelerated by the lender due to our default on the indebtedness. As of September 30, 2017 , we had not breached the provisions of these agreements. If we had breached these provisions, we could have been required to settle our obligations under the agreements at the termination value of $2.8 million . Although our derivative contracts are subject to master netting arrangements, which serve as credit mitigants to both us and our counterparties under certain situations, we do not net our derivative fair values or any existing rights or obligations to cash collateral on the Condensed Consolidated Balance Sheets. We did not have any asset or liability derivative balances that were offsetting that would have resulted in reported net derivative balances differing from the recorded gross amount of derivative assets of $2.0 million and $2.4 million (excluding the preferred stock embedded derivative) as of September 30, 2017 and December 31, 2016 , respectively, or gross recorded derivative liabilities of $2.6 million and $7.6 million as of September 30, 2017 and December 31, 2016 , respectively. Other Comprehensive Income MAA's other comprehensive income consists entirely of gains and losses attributable to the effective portion of our cash flow hedges. The chart below shows the change in the balance for the nine months ended September 30, 2017 and 2016 (dollars in thousands): Changes in Accumulated Other Comprehensive Income (Loss) by Component Affected Line Item in the Condensed Consolidated Statements Of Operations Gains and Losses on Cash Flow Hedges For the nine months ended September 30, 2017 2016 Beginning balance $ 1,144 $ (1,589 ) Other comprehensive income (loss) before reclassifications (1,252 ) (3,840 ) Amounts reclassified from accumulated other comprehensive income (interest rate contracts) Interest expense 884 3,359 Net current-period other comprehensive loss attributable to noncontrolling interests 14 25 Net current-period other comprehensive loss attributable to MAA (354 ) (456 ) Ending balance $ 790 $ (2,045 ) See also discussions in Note 9 to the Condensed Consolidated Financial Statements.

Fair Value Disclosure of Financ

Fair Value Disclosure of Financial Instruments	9 Months Ended
	Sep. 30, 2017
Notes To Financial Statements [Abstract]
Fair Value Disclosure of Financial Instruments	Fair Value Disclosure of Financial Instruments Cash and cash equivalents, restricted cash, accounts payable, accrued expenses and other liabilities and security deposits are carried at amounts that reasonably approximate their fair value due to their short term nature. We apply Financial Accounting Standard Board, or FASB, ASC 820 Fair Value Measurements and Disclosures, or ASC 820. ASC 820 defines fair value, establishes a framework for measuring fair value, and expands disclosures about fair value measurements. ASC 820 applies to reported balances that are required or permitted to be measured at fair value under existing accounting pronouncements; accordingly, the standard does not require any new fair value measurements of reported balances. ASC 820 emphasizes that fair value is a market-based measurement, not an entity-specific measurement. Therefore, a fair value measurement should be determined based on the assumptions that market participants would use in pricing the asset or liability. As a basis for considering market participant assumptions in fair value measurements, ASC 820 establishes a fair value hierarchy that distinguishes between market participant assumptions based on market data obtained from sources independent of the reporting entity (observable inputs that are classified within Levels 1 and 2 of the hierarchy) and the reporting entity’s own assumptions about market participant assumptions (unobservable inputs classified within Level 3 of the hierarchy). Level 1 inputs utilize quoted prices (unadjusted) in active markets for identical assets or liabilities that we have the ability to access. Level 2 inputs are inputs other than quoted prices included in Level 1 that are observable for the asset or liability, either directly or indirectly. Level 2 inputs may include quoted prices for similar assets and liabilities in active markets, as well as inputs that are observable for the asset or liability (other than quoted prices), such as interest rates, foreign exchange rates, and yield curves that are observable at commonly quoted intervals. Level 3 inputs are unobservable inputs for the asset or liability, which are typically based on an entity’s own assumptions, as there is little, if any, related market activity. In instances where the determination of the fair value measurement is based on inputs from different levels of the fair value hierarchy, the level in the fair value hierarchy within which the entire fair value measurement falls is based on the lowest level input that is significant to the fair value measurement in its entirety. Our assessment of the significance of a particular input to the fair value measurement in its entirety requires judgment, and considers factors specific to the asset or liability. Fixed rate notes payable at September 30, 2017 and December 31, 2016 , totaled $3.23 billion and $3.00 billion , respectively, and had estimated fair values of $3.41 billion and $3.13 billion (excluding prepayment penalties), respectively, as of September 30, 2017 and December 31, 2016 . The carrying values of variable rate notes payable (excluding the effect of interest rate swap and cap agreements) at September 30, 2017 and December 31, 2016 , totaled $1.3 billion and $1.5 billion , respectively, and had estimated fair values of $1.3 billion and $1.5 billion (excluding prepayment penalties), respectively, as of September 30, 2017 and December 31, 2016 . The valuation of our debt is determined using widely accepted valuation techniques, including discounted cash flow analysis on the expected cash flows of each debt instrument. This analysis reflects the contractual terms of the debt, and uses observable market-based inputs, including interest rate curves and credit spreads. The fair values of fixed rate debt are determined by using the present value of future cash outflows discounted with the applicable current market rate plus a credit spread. The fair values of variable rate debt are determined using the stated variable rate plus the current market credit spread. Our variable rates reset every 30 to 90 days and we conclude that these rates reasonably estimate current market rates. We have determined that inputs used to value our debt fall within Level 2 of the fair value hierarchy and therefore our fair market valuation of debt is considered Level 2 in the fair value hierarchy. Financial Instruments Carried at Fair Value Currently, we use interest rate swaps and interest rate caps (options) to manage our interest rate risk. The valuation of these instruments is determined using widely accepted valuation techniques, including discounted cash flow analysis on the expected cash flows of each derivative. This analysis reflects the contractual terms of the derivatives, including the period to maturity, and uses observable market-based inputs, including interest rate curves and implied volatilities. The fair values of interest rate swaps are determined using the market standard methodology of netting the discounted future fixed cash receipts (or payments) and the discounted expected variable cash payments (or receipts). The variable cash payments (or receipts) are based on an expectation of future interest rates (forward curves) derived from observable market interest rate curves. The fair values of interest rate options are determined using the market standard methodology of discounting the future expected cash receipts that would occur if variable interest rates rise above the strike rate of the caps. The variable interest rates used in the calculation of projected receipts on the cap are based on an expectation of future interest rates derived from observable market interest rate curves and volatilities. To comply with the provisions of ASC 820, we incorporate credit valuation adjustments to appropriately reflect both our own nonperformance risk and the respective counterparty’s nonperformance risk in the fair value measurements. In adjusting the fair value of our derivative contracts for the effect of nonperformance risk, we have considered the impact of netting and any applicable credit enhancements, such as collateral postings, thresholds, mutual puts and guarantees. In conjunction with the FASB's fair value measurement guidance, we made an accounting policy election to measure the credit risk of our derivative financial instruments that are subject to master netting agreements on a net basis by counterparty portfolio. The derivative asset related to the redemption feature embedded in the MAA Series I preferred stock issued in connection with Merger is valued using widely accepted valuation techniques, including discounted cash flow analysis in which the perpetual value of the preferred shares is compared to the value with the call option giving the value of the bifurcated call option as the difference between the two values. This analysis reflects the contractual terms of the redeemable preferred shares, redeemable at the Company's option, on October 1, 2026 , reflecting the redemption price per share, $50 , as the price at which the preferred stock is redeemable. The analysis uses observable market-based inputs, including discount rates based on trading data available on the preferred shares to interpolate an as called value and adjusted based treasury rates to determine the present value of cash flows for the called value and the perpetual value in addition to market data available on the preferred shares to interpolate an as called value and discount rate and again adjusted from there to determine the perpetual discount rate using the applicable treasury rates. We have determined that the majority of the inputs used to value our derivatives fall within Level 2 of the fair value hierarchy, and as a result, all of our derivatives held as of September 30, 2017 and December 31, 2016 were classified as Level 2 in the fair value hierarchy. The tables below present our assets and liabilities measured at fair value on a recurring basis as of September 30, 2017 and December 31, 2016 , aggregated by the level in the fair value hierarchy within which those measurements fall. Assets and Liabilities Measured at Fair Value on a Recurring Basis at September 30, 2017 (dollars in thousands) Balance Sheet Location Quoted Prices in Significant Significant Balance at September 30, 2017 Assets Interest rate derivative contracts Other assets $ — $ 2,043 $ — $ 2,043 Preferred stock embedded derivative Other assets — 18,190 — 18,190 Total $ — $ 20,233 $ — $ 20,233 Liabilities Interest derivative rate contracts Fair market value of interest rate swaps $ — $ 2,602 $ — $ 2,602 Assets and Liabilities Measured at Fair Value on a Recurring Basis at December 31, 2016 (dollars in thousands) Balance Sheet Location Quoted Prices in Significant Significant Balance at December 31, 2016 Assets Interest rate derivative contracts Other assets $ — $ 2,364 $ — $ 2,364 Preferred stock embedded derivative Other assets — 10,783 — 10,783 Total $ — $ 13,147 $ — $ 13,147 Liabilities Interest derivative rate contracts Fair market value of interest rate swaps $ — $ 7,562 $ — $ 7,562 The fair value estimates presented herein are based on information available to management as of September 30, 2017 and December 31, 2016 . These estimates are not necessarily indicative of the amounts we could ultimately realize. See also discussions in Note 8 to the Condensed Consolidated Financial Statements.

Shareholders' Equity of MAA

Shareholders' Equity of MAA	9 Months Ended
	Sep. 30, 2017
Shareholders' Equity of MAA [Abstract]
Stockholders' Equity Note Disclosure [Text Block]	Shareholders' Equity of MAA On September 30, 2017 , 113,627,014 shares of common stock of MAA and 4,200,032 OP Units in the Operating Partnership (excluding the OP Units held by MAA) were issued and outstanding, representing a total of 117,827,046 common shares and units. At September 30, 2016 , 75,542,583 shares of common stock of MAA and 4,143,203 OP Units in the Operating Partnership (excluding OP Units held by MAA) were issued and outstanding, representing a total of 79,685,786 common shares and units. There were 108,438 options to acquire shares of MAA common stock outstanding as of September 30, 2017 , as compared to 39,084 outstanding options as of September 30, 2016 . During the nine months ended September 30, 2017 , 47,956 shares of MAA common stock were acquired from employees to satisfy minimum tax withholding obligations that arose upon vesting of restricted stock granted pursuant to approved plans. During the nine months ended September 30, 2016 , 19,727 shares were acquired for that purpose. During the nine months ended September 30, 2017 , we issued 10,340 shares related to the exercise of stock options. These exercises resulted in proceeds of $0.4 million . During the nine months ended September 30, 2016 , there were no stock options exercised. Preferred Stock As of September 30, 2017 , MAA had one outstanding series of cumulative redeemable preferred stock which has the following characteristics: Description Outstanding Shares Liquidation Preference (1) Optional Redemption Date Redemption Price (2) Stated Dividend Yield Dividend Rate (per share) (per share) (per share) (per share) Series I 867,846 $50.00 10/1/2026 $50.00 8.50% $4.25 (1) The total liquidation preference for outstanding preferred stock is $43.4 million . (2) The redemption price is the price at which the preferred stock is redeemable, at MAA's option, for cash.

Partners' Capital of Mid-Americ

Partners' Capital of Mid-America Apartments, L.P.	9 Months Ended
	Sep. 30, 2017
Partners' Capital of Mid-America Apartments, L.P. [Abstract]
Partners' Capital Notes Disclosure [Text Block]	Partners' Capital of MAALP Operating Partnership Units Interests in MAALP are represented by OP Units. As of September 30, 2017 , there were 117,827,046 OP Units outstanding, 113,627,014 or 96.4% of which were owned by MAA, MAALP's general partner. The remaining 4,200,032 OP Units were owned by non-affiliated limited partners, or Class A Limited Partners. As of September 30, 2016 , there were 79,685,786 OP Units outstanding, 75,542,583 or 94.8% of which were owned by MAA and 4,143,203 of which were owned by the Class A Limited Partners. MAA, as the sole general partner of MAALP, has full, complete and exclusive discretion to manage and control the business of the Operating Partnership subject to the restrictions specifically contained within the Operating Partnership's agreement of limited partnership, or the Partnership Agreement. Unless otherwise stated in the Partnership Agreement, this power includes, but is not limited to, acquiring, leasing, or disposing of any real property; constructing buildings and making other improvements to properties owned; borrowing money, modifying or extinguishing current borrowings, issuing evidence of indebtedness, and securing such indebtedness by mortgage, deed of trust, pledge or other lien on the Operating Partnership's assets; and distribution of Operating Partnership cash or other assets in accordance with the Partnership Agreement. MAA can generally, at its sole discretion, issue and redeem OP Units and determine the consideration to be received or the redemption price to be paid, as applicable. MAA may delegate these and other powers granted if MAA, the general partner, remains in supervision of the designee. Under the Partnership Agreement, the Operating Partnership may issue Class A Units and Class B Units. Class A Units may only be held by limited partners who are not affiliated with MAA, in its capacity as general partner of the Operating Partnership, while Class B Units may only be held by MAA, in its capacity as general partner of the Operating Partnership, and as of September 30, 2017 , a total of 4,200,032 Class A Units in the Operating Partnership were held by limited partners unaffiliated with MAA, while a total of 113,627,014 Class B Units were held by MAA. In general, the limited partners do not have the power to participate in the management or control of the Operating Partnership's business except in limited circumstances including changes in the general partner and protective rights if the general partner acts outside of the provisions provided in the Partnership Agreement. The transferability of Class A Units is also limited by the Partnership Agreement. Net income (after allocations to preferred ownership interests) is allocated to the general partner and limited partners based on their respective ownership percentages of the Operating Partnership. Issuance or redemption of additional Class A Units or Class B Units changes the relative ownership percentage of the partners. The issuance of Class B Units generally occurs when MAA issues common stock and the proceeds from that issuance are contributed to the Operating Partnership in exchange for the issuance to MAA of a number of OP Units equal to the number of shares of common stock issued. Likewise, if MAA repurchases or redeems outstanding shares of common stock, the Operating Partnership generally redeems an equal number of Class B Units with similar terms held by MAA for a redemption price equal to the purchase price of those shares of common stock. At each reporting period, the allocation between general partner capital and limited partner capital is adjusted to account for the change in the respective percentage ownership of the underlying capital of the Operating Partnership. Holders of the Class A Units may require MAA to redeem their Class A Units, in which case MAA may, at its option, pay the redemption price either in cash (in an amount per Class A Unit equal, in general, to the average closing price of MAA's common stock on the NYSE over a specified period prior to the redemption date) or by delivering one share of MAA common stock (subject to adjustment under specified circumstances) for each Class A Unit so redeemed. At September 30, 2017 , a total of 4,200,032 Class A Units were outstanding and redeemable for 4,200,032 shares of MAA common stock, with an approximate value of $448.9 million , based on the closing price of MAA’s common stock on the NYSE on September 29, 2017, of $106.88 per share. At September 30, 2016 , a total of 4,143,203 Class A Units were outstanding and redeemable for 4,143,203 shares of MAA common stock, with an approximate value of $389.4 million , based on the closing price of MAA’s common stock on the NYSE on September 30, 2016 of $93.99 per share. The Operating Partnership pays the same per unit distribution in respect to the OP Units as the per share dividend MAA pays in respect to its common stock.

Legal Proceedings

Legal Proceedings	9 Months Ended
	Sep. 30, 2017
Legal Proceedings [Line Items]
Legal Matters and Contingencies [Text Block]	Legal Proceedings In September 2010, the United States Department of Justice, or DOJ, filed suit against Post Properties (and by virtue of the Merger, MAA) in the United States District Court for the District of Columbia alleging that certain of Post Properties’ apartments violated accessibility requirements of the Fair Housing Act, or FHA, and the Americans with Disabilities Act of 1990, or ADA. The DOJ is seeking, among other things, an injunction against MAA, requiring MAA to retrofit the properties and comply with FHA and ADA standards in future design and construction, as well as monetary damages and civil penalties. No trial date has been set. We are subject to various legal proceedings and claims that arise in the ordinary course of our business operations. Matters which arise out of allegations of bodily injury, property damage, and employment practices are generally covered by insurance. While the resolution of these other matters cannot be predicted with certainty, management currently believes, either individually or in the aggregate, the final outcome of such matters will not have any additional material adverse effect on our financial position, results of operations or cash flows. Loss Contingencies The outcomes of the claims, disputes and legal proceedings described or referenced above are subject to significant uncertainty. We record an accrual for loss contingencies when a loss is probable and the amount of the loss can be reasonably estimated. We review these accruals quarterly and make revisions based on changes in facts and circumstances. When a loss contingency is not both probable and reasonably estimable, we do not accrue the loss. However, if the loss (or an additional loss in excess of the accrual) is at least a reasonable possibility and material, then we disclose a reasonable estimate of the possible loss, or range of loss, if such reasonable estimate can be made. If we cannot make a reasonable estimate of the possible loss, or range of loss, then a statement to that effect is disclosed. The assessment of whether a loss is probable or a reasonable possibility, and whether the loss or range of loss is reasonably estimable, often involves a series of complex judgments about future events. Among the factors that we consider in this assessment, including with respect to the matters disclosed in this Note, are the nature of existing legal proceedings and claims, the asserted or possible damages or loss contingency (if reasonably estimable), the progress of the matter, existing law and precedent, the opinions or views of legal counsel and other advisers, our experience in similar matters, the facts available to us at the time of assessment, and how we intend to respond, or have responded, to the proceeding or claim. Our assessment of these factors may change over time as individual proceedings or claims progress. For matters where we are not currently able to reasonably estimate a range of reasonably possible loss, the factors that have contributed to this determination include the following: (i) the damages sought are indeterminate; (ii) the proceedings are in the early stages; (iii) the matters involve novel or unsettled legal theories or a large or uncertain number of actual or potential cases or parties; and/or (iv) discussions with the parties in matters that are expected ultimately to be resolved through negotiation and settlement have not reached the point where we believe a reasonable estimate of loss, or range of loss, can be made. In such instances, we believe that there is considerable uncertainty regarding the timing or ultimate resolution of such matters, including a possible eventual loss or business impact, if any. As of September 30, 2017 and December 31, 2016 , the Company's accrual for loss contingencies was $35.1 million and $42.1 million in the aggregate, respectively.

Segment Information

Segment Information	9 Months Ended
	Sep. 30, 2017
Notes To Financial Statements [Abstract]
Segment Information	Segment Information As of September 30, 2017 , we owned or had ownership interest in 303 multifamily apartment communities in 17 different states and the District of Columbia from which we derived all significant sources of earnings and operating cash flows. Senior management evaluates performance and determines resource allocations of each of our apartment communities on a Large Market Same Store, Secondary Market Same Store, and Non-Same Store and Other basis, as well as an individual apartment community basis. This is consistent with the aggregation criteria under GAAP as each of our apartment communities generally has similar economic characteristics, facilities, services, and tenants. The following are the three reportable operating segments for MAA and the Operating Partnership: • Large market same store communities are generally communities in markets with a population of at least 1 million and at least 1% of the total public multifamily REIT units that we have owned and have been stabilized for at least a full 12 months. • Secondary market same store communities are generally communities in markets with populations of more than 1 million but less than 1% of the total public multifamily REIT units or markets with populations of less than 1 million that we have owned and have been stabilized for at least a full 12 months. • Non-same store communities and other includes recent acquisitions, communities in development or lease-up, communities that have been identified for disposition, and communities that have undergone a significant casualty loss. Also included in non-same store communities are non-multifamily activities. On the first day of each calendar year, we determine the composition of our same store operating segments for that year as well as adjust the previous year, which allows us to evaluate full period-over-period operating comparisons. Properties in development or lease-up will be added to the same store portfolio on the first day of the calendar year after they have been owned and stabilized for at least a full 12 months. Communities are considered stabilized after achieving 90% occupancy for 90 days . Communities that have been identified for disposition are excluded from our same store portfolio. We utilize NOI in evaluating the performance of the segments. Total NOI represents total property revenues less total property operating expenses, excluding depreciation and amortization, for all properties held during the period regardless of their status as held for sale. We believe NOI is a helpful tool in evaluating the operating performance of our segments because it measures the core operations of property performance by excluding corporate level expenses and other items not related to property operating performance. All properties acquired from Post Properties have been placed in our Non-Same Store and Other operating segment, as the properties are recent acquisitions and have not been owned and stabilized for at least 12 months as of the first day of the current calendar year. Revenues and NOI for each reportable segment for the three- and nine- month periods ended September 30, 2017 and 2016 were as follows (dollars in thousands): Three months ended September 30, Nine months ended September 30, 2017 2016 2017 2016 Revenues: Large Market Same Store $ 169,105 $ 165,046 $ 503,076 $ 487,725 Secondary Market Same Store 87,895 85,822 261,272 254,685 Non-Same Store and Other 127,550 26,030 381,901 75,740 Total operating revenues $ 384,550 $ 276,898 $ 1,146,249 $ 818,150 NOI: Large Market Same Store $ 104,574 $ 101,595 $ 313,419 $ 302,230 Secondary Market Same Store 53,836 53,124 162,617 159,263 Non-Same Store and Other 76,961 15,533 233,792 46,175 Total NOI 235,371 170,252 709,828 507,668 Depreciation and amortization (117,928 ) (76,959 ) (374,285 ) (227,829 ) Acquisition expenses — (1,033 ) — (2,167 ) Property management expenses (10,281 ) (7,908 ) (32,007 ) (25,221 ) General and administrative expenses (8,361 ) (6,661 ) (30,735 ) (20,257 ) Merger related expenses (128 ) (3,901 ) (3,977 ) (3,901 ) Integration costs (4,002 ) — (10,521 ) — Interest and other non-property income 4,303 64 7,632 159 Interest expense (39,940 ) (32,168 ) (115,005 ) (96,418 ) Gain on debt extinguishment/modification 828 — 3,168 3 Gain on sale of depreciable real estate assets 58,844 47,749 59,045 48,572 Net casualty gain (loss) after insurance and other settlement proceeds 564 (75 ) 233 738 Income tax expense (641 ) (454 ) (1,910 ) (1,200 ) (Loss) gain on sale of non-depreciable real estate assets (6 ) — 42 2,170 Gain from real estate joint ventures 335 — 1,021 27 Net income attributable to noncontrolling interests (4,249 ) (4,627 ) (7,600 ) (9,508 ) Preferred Dividends (922 ) — (2,766 ) — Net income available for MAA common shareholders $ 113,787 $ 84,279 $ 202,163 $ 172,836 Assets for each reportable segment as of September 30, 2017 and December 31, 2016 were as follows (dollars in thousands): September 30, 2017 December 31, 2016 Assets: Large Market Same Store $ 4,038,127 $ 4,126,885 Secondary Market Same Store 1,731,050 1,768,183 Non-Same Store and Other 5,527,583 5,479,780 Corporate assets 236,041 229,643 Total assets $ 11,532,801 $ 11,604,491

Real Estate Acquisitions and Di

Real Estate Acquisitions and Dispositions	9 Months Ended
	Sep. 30, 2017
Notes To Financial Statements [Abstract]
Real Estate Acquisitions and Dispositions	Real Estate Acquisitions and Dispositions The following chart shows our acquisition activity for the nine months ended September 30, 2017 : Community Market Units Date Acquired Charlotte at Midtown Nashville, TN 279 March 16, 2017 The following chart shows our disposition activity for the nine months ended September 30, 2017 : Community Market Units or Acres Date Sold Lakewood Ranch - Outparcel Tampa, FL 12 acres April 7, 2017 Post Alexander - Outparcel Atlanta, GA 1 acre June 12, 2017 Paddock Club Lakeland Lakeland, FL 464 July 13, 2017 Paddock Club Lakeland - Outparcel Lakeland, FL 9 acres July 13, 2017 Paddock Club Montgomery Montgomery, AL 208 July 20, 2017 Northwood Place Fort Worth, TX 270 July 20, 2017 Town Park Lot 12 Orlando, FL 1 acre August 7, 2017

Recent Accounting Pronouncement

Recent Accounting Pronouncements	9 Months Ended
	Sep. 30, 2017
Notes To Financial Statements [Abstract]
Recent Accounting Pronouncements	Recent Accounting Pronouncements The following table provides a brief description of recent accounting pronouncements that could have a material effect on our financial statements: Standard Description Date of Adoption Effect on the Financial Statements or Other Significant Matters ASU 2014-09, Revenue from Contracts with Customers This ASU establishes principles for recognizing revenue upon the transfer of promised goods or services to customers, in an amount that reflects the expected consideration received in exchange for those goods or services as outlined in a five-step model whereby revenue is recognized as performance obligations within a contract are satisfied. Income from lease contracts is specifically excluded from this ASU. This ASU is effective for annual reporting periods beginning after December 15, 2017, as a result of a deferral of the effective date arising from the issuance of ASU 2015-14, Revenue from Contracts with Customers - Deferral of the Effective Date . Early adoption is permitted. The amendments may be applied using the full retrospective transition method or by using the modified retrospective transition method with a cumulative effect recognized as of the date of initial application. We will adopt ASU 2014-09 effective January 1, 2018, using the modified retrospective approach. The majority of our revenue is derived from real estate lease contracts, which falls under ASU 2016-02, Leases . Our analysis on non-lease related revenues, which comprise approximately 10% of consolidated revenues, indicates the adoption of this ASU will not have a material impact on our consolidated financial statements and internal accounting policies. ASU 2016-02, Leases This ASU amends existing accounting standards for lease accounting and establishes the principles for lease accounting for both the lessee and lessor. The amendment requires an entity to recognize a right-of-use asset and lease liability for all leases with terms of more than 12 months. Recognition, measurement and presentation of expenses will depend on classification as a finance or operating lease. The amendment also requires certain quantitative and qualitative disclosures about leasing arrangements. This ASU is effective for annual reporting periods beginning after December 15, 2018; however, early adoption is permitted. The standard must be adopted using a modified retrospective transition and provides for certain practical expedients. Transition will require application of the new guidance at the beginning of the earliest comparative period presented. We are currently evaluating the impact this standard may have on our consolidated financial statements and related disclosures upon adoption. ASU 2016-09, Improvements to Employee Share-Based Payment Accounting This ASU amends existing accounting standards for certain aspects of share-based payments to employees. The new guidance will require all income tax effects of awards to be recognized in the income statement when the awards vest or are settled. It also will allow an employer to repurchase more of an employee’s shares than it can today for tax withholding purposes without triggering liability accounting and to make a policy election to account for forfeitures as they occur. This ASU is effective for annual reporting periods beginning after December 15, 2016. We adopted this guidance effective January 1, 2017. We adopted this standard effective January 1, 2017, using the modified retrospective transition method, with a cumulative-effect adjustment to retained earnings, and there was no material effect on our consolidated financial position or results of operations taken as a whole. Standard Description Date of Adoption Effect on the Financial Statements or Other Significant Matters ASU 2016-15, Classification of Certain Cash Receipts and Cash Payments (a consensus of the Emerging Issues Task Force) This ASU clarifies how several specific cash receipts and cash payments are to be presented and classified on the statement of cash flows, including debt prepayment or debt extinguishment costs, settlement of zero-coupon debt instruments, contingent consideration made after a business combination, distributions received from equity method investees, beneficial interests in securitization transactions, and separately identifiable cash flows and application of predominance principle. This ASU is effective for interim and annual periods beginning after December 15, 2017, and early adoption is permitted. Each amendment in this standard must be applied prospectively, retrospectively, or as of the beginning of the earliest comparative period presented in the year of adoption, depending on the type of amendment. We expect to adopt ASU 2016-15 as of January 1, 2018. We have determined that three of the eight transactions in the update are relevant to MAA and its cash flows, including: 1) debt prepayment or debt extinguishment costs, 2) proceeds from the settlement of insurance claims and 3) distributions received from equity method investees. We performed an analysis and determined that only the change in classification of debt prepayment or debt extinguishment costs, which we currently report in operating activities, will have a material impact on the statement of cash flows. Upon adoption in Q1 2018, $1.6 million of cash outflows for debt prepayment or extinguishment costs currently reported in net cash provided by operating activities for the nine months ended September 30, 2017, will be re-classified to and reported in net cash used in financing activities. ASU 2016-18, Statement of Cash Flows (Topic 230):Restricted Cash (A Consensus of the FASB Emerging Issues Task Force) This ASU requires restricted cash to be presented with cash and cash equivalents when reconciling the beginning and ending amounts in the statements of cash flows. This ASU is effective for interim and annual periods beginning after December 15, 2017, and early adoption is permitted. The update should be applied retrospectively to each period presented. We expect to adopt ASU 2016-18 as of January 1, 2018. We currently report the change in restricted cash within the operating and investing activities in our consolidated statement of cash flows. Upon adoption in Q1 2018, cash and cash equivalents reported in our consolidated statements of cash flows for the nine months ended September 30, 2017 will increase by approximately $80.3 million to reflect the restricted cash balances. Additionally, net cash used in investing activities will decrease by $10.6 million for the nine months ended September 30, 2017. ASU 2017-01, Clarifying the Definition of a Business (Topic 805) This ASU clarifies the definition of a business and provides further guidance for evaluating whether a transaction will be accounted for as an acquisition of an asset or a business. This ASU is effective for interim and annual periods beginning after December 15, 2017. We early adopted this standard effective January 1, 2017. We adopted this standard as of January 1, 2017 and the adoption did not require any additional disclosures. We believe most of our future acquisitions of operating properties will qualify as asset acquisitions and most future transaction costs associated with these acquisitions will be capitalized. Through the third quarter of 2017, acquisition costs totaling $0.6 million related to our acquisition of Charlotte at Midtown were capitalized and allocated to the assets acquired based on the relative fair market value of those underlying assets. ASU 2017-12, Derivatives and Hedging (Topic 815) This ASU clarifies hedge accounting requirements, improves disclosure of hedging arrangements, and better aligns risk management activities and financial reporting for hedging relationships. This ASU is effective for interim and annual periods beginning after December 15, 2018, and early adoption is permitted. The standard should be adopted using a modified retrospective approach. We are currently evaluating the impact this standard may have on our consolidated financial statements and related disclosures upon adoption.

Basis of Presentation and Pri23

Basis of Presentation and Principles of Consolidation (Policies)	9 Months Ended
	Sep. 30, 2017
Basis of Presentation and Principles of Consolidation [Abstract]
Basis Of Presentation And Principles Of Consolidation Policy [Policy Text Block]	Basis of Presentation and Principles of Consolidation The accompanying Condensed Consolidated Financial Statements have been prepared by our management in accordance with United States generally accepted accounting principles, or GAAP, and applicable rules and regulations of the Securities and Exchange Commission, or the SEC. The Condensed Consolidated Financial Statements of MAA presented herein include the accounts of MAA, the Operating Partnership, and all other subsidiaries in which MAA has a controlling financial interest. MAA owns approximately 92.5% to 100% of all consolidated subsidiaries, including the Operating Partnership. The Condensed Consolidated Financial Statements of MAALP presented herein include the accounts of MAALP and all other subsidiaries in which MAALP has a controlling financial interest. MAALP owns, directly or indirectly, 92.5% to 100% of all consolidated subsidiaries. In our opinion, all adjustments necessary for a fair presentation of the Condensed Consolidated Financial Statements have been included, and all such adjustments were of a normal recurring nature. All significant intercompany accounts and transactions have been eliminated in consolidation. We invest in entities which may qualify as variable interest entities, or VIEs, and MAALP is considered a VIE. A VIE is a legal entity in which the equity investors lack sufficient equity at risk for the entity to finance its activities without additional subordinated financial support or, as a group, the holders of the equity investment at risk lack the power to direct the activities of a legal entity as well as the obligation to absorb its expected losses or the right to receive its expected residual returns. MAALP is classified as a VIE, since the limited partners lack substantive kick-out rights and substantive participating rights. We consolidate all VIEs for which we are the primary beneficiary and use the equity method to account for investments that qualify as VIEs but for which we are not the primary beneficiary. In determining whether we are the primary beneficiary of a VIE, we consider qualitative and quantitative factors, including but not limited to, those activities that most significantly impact the VIE's economic performance and which party controls such activities. We use the equity method of accounting for our investments in entities for which we exercise significant influence, but do not have the ability to exercise control. The factors considered in determining that we do not have the ability to exercise control include ownership of voting interests and participatory rights of investors (see "Investment in Unconsolidated Real Estate Joint Ventures" below). Noncontrolling Interests At September 30, 2017 , the Company had two types of noncontrolling interests, (1) noncontrolling interests related to the common unitholders of the Operating Partnership (see Note 11) and (2) noncontrolling interests related to its consolidated real estate entities (see "Investment in Consolidated Real Estate Joint Ventures" below). Investment in Unconsolidated Joint Ventures Immediately prior to the effective date of the Merger, Post Properties together with other institutional investors, in a limited liability company, or the Apartment LLC, owned one apartment community, Post Massachusetts Avenue, located in Washington, D.C. Post Properties had a 35.0% equity interest in this unconsolidated joint venture, which we retained immediately following the effectiveness of the Merger and as of September 30, 2017 . We provide property and asset management services to the Apartment LLC for which we earn fees. This joint venture was determined to be a VIE, but we are not designated as a primary beneficiary. As a result, we account for our investment in the Apartment LLC using the equity method of accounting, as we are able to exert significant influence, but do not have a controlling interest in this joint venture. At September 30, 2017 , our investment in the Apartment LLC totaled $45.1 million . During September 2017, MAA entered into a limited partnership together with a general partner and other limited partners to form Real Estate Technology Ventures, L.P. MAA's equity interest in the partnership is 32.0% , which is considered more than minor. This joint venture was determined to be a VIE, but we are not designated as a primary beneficiary. Therefore, we account for our investment in the limited partnership using the equity method of accounting, as we are able to exert significant influence over the partnership but do not have a controlling interest in this joint venture. At September 30, 2017 , our investment in the limited partnership totaled $0.8 million , and we are committed to make additional capital contributions totaling $14.2 million over the next five years from the date of the initial capital contribution. Investment in Consolidated Real Estate Joint Ventures In 2015, Post Properties entered into a joint venture arrangement with a private real estate company to develop, construct and operate a 358 -unit apartment community in Denver, Colorado. At September 30, 2017 , we owned a 92.5% equity interest in the consolidated joint venture. In 2015, this joint venture acquired the land site and initiated the development of the apartment community. The venture partner will generally be responsible for the development and construction of the community and we will continue to manage the community upon its completion. This joint venture was determined to be a VIE with us designated as the primary beneficiary. As a result, the accounts of the joint venture are consolidated by us. At September 30, 2017 , our consolidated assets, liabilities and equity included construction in progress of $60.3 million , land of $14.5 million , and accounts payable and accrued expenses of $6.2 million . Assets Held for Sale During September 2017, one land parcel was classified as held for sale. The criteria for classifying the land parcel as held for sale were met during June; however, the sale is not expected to close until the fourth quarter of 2017. As a result, the assets and liabilities associated with the land parcel were presented as held for sale in the Condensed Consolidated Balance Sheets.

Business Combinations Business

Business Combinations Business Combinations (Tables)	9 Months Ended
	Sep. 30, 2017
Business Combinations [Abstract]
Purchase Price Allocation Schedule [Table Text Block]	Land $ 875,294 Buildings and improvements 3,397,342 Furniture, fixtures and equipment 81,243 Development and capital improvements in progress 183,881 Undeveloped land 24,200 Commercial properties, net 3,610 Investment in real estate joint venture 44,435 Lease intangible assets 53,192 Cash and cash equivalents 34,292 Restricted cash 3,608 Deferred costs and other assets, excluding lease intangible assets 41,803 Total assets acquired 4,742,900 Notes payable (595,609) Fair market value of interest rate swaps (2,118) Lease intangible liabilities (1,661) Accounts payable, accrued expenses, and other liabilities (132,613) Total liabilities assumed, including debt (732,001 ) Noncontrolling interests - consolidated real estate entity (2,306 ) Total purchase price $ 4,008,593

Earnings Per Common Share of 25

Earnings Per Common Share of MAA (Tables)	9 Months Ended
	Sep. 30, 2017
Earnings Per Common Share of MAA [Abstract]
Schedule of Calculation of Numerator and Denominator in Earnings Per Share [Table Text Block]	Basic earnings per share is computed by dividing net income available for MAA common shareholders by the weighted average number of shares outstanding during the period. All outstanding unvested restricted share awards contain rights to non-forfeitable dividends and participate in undistributed earnings with common shareholders and, accordingly, are considered participating securities that are included in the two-class method of computing basic earnings per share. Both the unvested restricted shares and other potentially dilutive common shares, and the related impact to earnings, are considered when calculating earnings per share on a diluted basis with our diluted earnings per share being the more dilutive of the treasury stock or two-class methods. OP Units are included in dilutive earnings per share calculations when they are dilutive to earnings per share. For the three and nine months ended September 30, 2017 and 2016 , MAA's basic earnings per share was computed using the two-class method, and MAA's diluted earnings per share was computed using the more dilutive of the treasury stock method or two-class method, as presented below: (dollars and shares in thousands, except per share amounts) Three months ended September 30, Nine months ended September 30, 2017 2016 2017 2016 Shares Outstanding Weighted average common shares - basic 113,434 75,302 113,392 75,276 Weighted average partnership units outstanding — (1) — (1) — (1) 4,156 Effect of dilutive securities 219 — (2) 270 246 Weighted average common shares - diluted 113,653 75,302 113,662 79,678 Calculation of Earnings per Share - basic Net income $ 118,958 $ 88,906 $ 212,529 $ 182,344 Net income attributable to noncontrolling interests (4,249 ) (4,627 ) (7,600 ) (9,508 ) Unvested restricted stock (allocation of earnings) (181 ) (254 ) (337 ) (485 ) Preferred dividends (922 ) — (2,766 ) — Net income available for common shareholders, adjusted $ 113,606 $ 84,025 $ 201,826 $ 172,351 Weighted average common shares - basic 113,434 75,302 113,392 75,276 Earnings per share - basic $ 1.00 $ 1.12 $ 1.78 $ 2.29 Calculation of Earnings per Share - diluted Net income $ 118,958 $ 88,906 $ 212,529 $ 182,344 Net income attributable to noncontrolling interests (4,249 ) (1) (4,628 ) (1) (7,600 ) (1) — Unvested restricted stock (allocation of earnings) — (254 ) (2) — — Preferred dividends (922 ) — (2,766 ) — Net income available for common shareholders, adjusted $ 113,787 $ 84,024 $ 202,163 $ 182,344 Weighted average common shares - diluted 113,653 75,302 113,662 79,678 Earnings per share - diluted $ 1.00 $ 1.12 $ 1.78 $ 2.29 (1) For both the three and nine months ended September 30, 2017 and the three months ended September 30, 2016 , 4.2 million OP Units and their related income are not included in the diluted earnings per share calculations as they are not dilutive. (2) For the three months ended September 30, 2016 , 0.2 million potentially dilutive securities and their related income are not included in the diluted earnings per share calculations as they are not dilutive.

Earnings Per OP Unit of MAALP (

Earnings Per OP Unit of MAALP (Tables)	9 Months Ended
	Sep. 30, 2017
Earnings Per OP Unit of MAALP [Abstract]
Schedule of Earnings Per Unit, Basic and Diluted [Table Text Block]	Basic earnings per OP Unit is computed by dividing net income available for common unitholders by the weighted average number of OP Units outstanding during the period. All outstanding unvested restricted unit awards contain rights to non-forfeitable distributions and participate in undistributed earnings with common unitholders and, accordingly, are considered participating securities that are included in the two-class method of computing basic earnings per OP unit. Diluted earnings per OP Unit reflects the potential dilution that could occur if securities or other contracts to issue OP Units were exercised or converted into OP Units. A reconciliation of the numerators and denominators of the basic and diluted earnings per OP Unit computations for the three and nine months ended September 30, 2017 and 2016 is presented below: (dollars and units in thousands, except per unit amounts) Three months ended September 30, Nine months ended September 30, 2017 2016 2017 2016 Units Outstanding Weighted average common units - basic 117,643 79,449 117,607 79,432 Effect of dilutive securities 219 — (1) 270 246 Weighted average common units - diluted 117,862 79,449 117,877 79,678 Calculation of Earnings per Unit - basic Net income $ 118,958 $ 88,906 $ 212,529 $ 182,344 Unvested restricted stock (allocation of earnings) (181 ) (254 ) (337 ) (484 ) Preferred unit distributions (922 ) — (2,766 ) — Net income available for common unitholders, adjusted $ 117,855 $ 88,652 $ 209,426 $ 181,860 Weighted average common units - basic 117,643 79,449 117,607 79,432 Earnings per common unit - basic $ 1.00 $ 1.12 $ 1.78 $ 2.29 Calculation of Earnings per Unit - diluted Net income $ 118,958 $ 88,906 $ 212,529 $ 182,344 Unvested restricted stock (allocation of earnings) — (254 ) (1) — — Preferred unit distributions (922 ) — (2,766 ) — Net income available for common unitholders, adjusted $ 118,036 $ 88,652 $ 209,763 $ 182,344 Weighted average common units - diluted 117,862 79,449 117,877 79,678 Earnings per common unit - diluted $ 1.00 $ 1.12 $ 1.78 $ 2.29 (1) For the three months ended September 30, 2016 , 0.2 million potentially dilutive securities and their related income are not included in the diluted earnings per share calculations as they are not dilutive.

MAA Equity (Tables)

MAA Equity (Tables)	9 Months Ended
	Sep. 30, 2017
MAA Equity [Abstract]
Shareholders' Equity [Table Text Block]	Mid-America Apartment Communities, Inc. Shareholders' Equity Preferred Stock Amount Common Stock Amount Additional Paid-In Capital Accumulated Distributions in Excess of Net Income Accumulated Other Comprehensive Income (Loss) Noncontrolling Noncontrolling Interest - Consolidated Real Estate Entity Total Equity EQUITY BALANCE DECEMBER 31, 2015 $ — $ 753 $ 3,627,074 $ (634,141 ) $ (1,589 ) $ 165,726 $ — $ 3,157,823 Net income attributable to controlling interest — — — 172,836 — 9,508 — 182,344 Other comprehensive loss - derivative instruments (cash flow hedges) — — — — (456 ) (25 ) — (481 ) Issuance and registration of common shares — 1 (739 ) — — — — (738 ) Shares repurchased and retired — — (1,811 ) — — — — (1,811 ) Shares issued in exchange for common units — — 780 — — (780 ) — — Shares issued in exchange for redeemable stock — — 122 — — — — 122 Redeemable stock fair market value adjustment — — — (296 ) — — — (296 ) Adjustment for noncontrolling interest ownership in operating partnership — — (38 ) — — 38 — — Amortization of unearned compensation — — 6,625 — — — — 6,625 Dividends on common stock ($2.46 per share) — — — (185,789 ) — — — (185,789 ) Dividends on noncontrolling interest units ($2.46 per unit) — — — — — (10,217 ) — (10,217 ) EQUITY BALANCE SEPTEMBER 30, 2016 $ — $ 754 $ 3,632,013 $ (647,390 ) $ (2,045 ) $ 164,250 $ — $ 3,147,582 Changes in total equity and its components for the nine-month periods ended September 30, 2017 and 2016 were as follows (dollars in thousands, except per share and per unit data): Mid-America Apartment Communities, Inc. Shareholders' Equity Preferred Stock Amount Common Stock Amount Additional Paid-In Capital Accumulated Distributions in Excess of Net Income Accumulated Other Comprehensive Income (Loss) Noncontrolling Interest Operating Partnership Noncontrolling Interest - Consolidated Real Estate Entity Total Equity EQUITY BALANCE DECEMBER 31, 2016 $ 9 $ 1,133 $ 7,109,012 $ (707,479 ) $ 1,144 $ 235,976 $ 2,306 $ 6,642,101 Net income attributable to controlling interest — — — 204,929 — 7,600 — 212,529 Other comprehensive income - derivative instruments (cash flow hedges) — — — — (354 ) (14 ) — (368 ) Issuance and registration of common shares — 1 153 — — — — 154 Issuance and registration of preferred shares — — 2,007 — — — — 2,007 Shares repurchased and retired — — (4,782 ) — — — — (4,782 ) Exercise of stock options — — 218 — — — — 218 Shares issued in exchange for common units — — 1,133 — — (1,133 ) — — Shares issued in exchange for redeemable stock — — 1,482 — — — — 1,482 Redeemable stock fair market value adjustment — — — (870 ) — — — (870 ) Adjustment for noncontrolling interest ownership in operating partnership — — 54 — — (54 ) — — Amortization of unearned compensation — — 8,552 (114 ) — — — 8,438 Dividends on preferred stock — — — (2,766 ) — — — (2,766 ) Dividends on common stock ($2.61 per share) — — — (296,535 ) — — — (296,535 ) Dividends on noncontrolling interest units ($2.61 per unit) — — — — — (10,982 ) — (10,982 ) EQUITY BALANCE SEPTEMBER 30, 2017 $ 9 $ 1,134 $ 7,117,829 $ (802,835 ) $ 790 $ 231,393 $ 2,306 $ 6,550,626

MAALP Capital (Tables)

MAALP Capital (Tables)	9 Months Ended
	Sep. 30, 2017
MAALP Capital [Abstract]
Partners' Capital [Table Text Block]	Changes in total capital and its components for the nine-month periods ended September 30, 2017 and 2016 were as follows (dollars in thousands, except per unit data): Mid-America Apartments, L.P. Unitholders' Capital Limited Partner General Partner Preferred Units Accumulated Noncontrolling Interest - Consolidated Real Estate Entity Total Partnership Capital CAPITAL BALANCE DECEMBER 31, 2016 $ 235,976 $ 6,337,721 $ 64,833 $ 1,246 $ 2,306 $ 6,642,082 Net income attributable to controlling interest 7,600 202,163 2,766 — — 212,529 Other comprehensive income - derivative instruments (cash flow hedges) — — — (368 ) — (368 ) Issuance of units — 154 2,007 — — 2,161 Units repurchased and retired — (4,782 ) — — — (4,782 ) Exercise of unit options — 218 — — — 218 General partner units issued in exchange for limited partner units (1,133 ) 1,133 — — — — Units issued in exchange for redeemable units — 1,482 — — — 1,482 Redeemable units fair market value adjustment — (870 ) — — — (870 ) Adjustment for limited partners' capital at redemption value (68 ) 68 — — — — Amortization of unearned compensation — 8,438 — — — 8,438 Distributions to preferred unitholders — — (2,766 ) — — (2,766 ) Distributions ($2.61 per unit) (10,982 ) (296,535 ) — — — (307,517 ) CAPITAL BALANCE SEPTEMBER 30, 2017 $ 231,393 $ 6,249,190 $ 66,840 $ 878 $ 2,306 $ 6,550,607 Mid-America Apartments, L.P. Unitholders' Capital Limited Partner General Partner Preferred Units Accumulated Noncontrolling Interest - Consolidated Real Estate Entity Total Partnership Capital CAPITAL BALANCE DECEMBER 31, 2015 $ 165,726 $ 2,993,696 $ — $ (1,618 ) $ — $ 3,157,804 Net income attributable to controlling interest 9,508 172,836 — — — 182,344 Other comprehensive loss - derivative instruments (cash flow hedges) — — — (481 ) — (481 ) Issuance of units — (738 ) — — — (738 ) Units repurchased and retired — (1,811 ) — — — (1,811 ) General partner units issued in exchange for limited partner units (780 ) 780 — — — — Units issued in exchange for redeemable units — 122 — — — 122 Redeemable units fair market value adjustment — (296 ) — — — (296 ) Adjustment for limited partners' capital at redemption value 13 (13 ) — — — — Amortization of unearned compensation — 6,625 — — — 6,625 Distributions ($2.46 per unit) (10,217 ) (185,789 ) — — — (196,006 ) CAPITAL BALANCE SEPTEMBER 30, 2016 $ 164,250 $ 2,985,412 $ — $ (2,099 ) $ — $ 3,147,563

Borrowings Borrowings (Tables)

Borrowings Borrowings (Tables)	9 Months Ended
	Sep. 30, 2017
Debt Disclosure [Abstract]
Schedule of Long-term Debt Instruments [Table Text Block]	Total Outstanding Debt The following table summarizes our indebtedness at September 30, 2017 (dollars in thousands): Borrowed Balance Effective Rate Average Contract Maturity Fixed Rate Secured Debt Individual property mortgages $ 933,256 4.0 % 9/11/2019 Variable Rate Secured Debt (1) Fannie Mae Facility 160,000 1.7 % 6/1/2018 Fair market value adjustments and debt issuance costs 16,717 Total Secured Debt 1,109,973 3.6 % 7/3/2019 Unsecured Debt Variable rate revolving credit facility 250,000 2.1 % 4/15/2020 Variable rate term loans 300,000 2.2 % 8/29/2020 Term loans fixed with swaps 550,000 3.0 % 4/17/2018 Fixed rate senior notes 2,310,000 4.0 % 10/24/2024 Fair market value adjustments, debt issuance costs and discounts (27,139 ) Total Unsecured Debt 3,382,861 3.5 % 1/18/2023 Total Outstanding Debt $ 4,492,834 3.5 % 2/13/2022 (1) Includes capped balances.

Derivatives and Hedging Activ30

Derivatives and Hedging Activities (Tables)	9 Months Ended
	Sep. 30, 2017
Notes To Financial Statements [Abstract]
Outstanding Interest Rate Derivatives Designated as Cash Flow Hedges of Interest Rate Risk	As of September 30, 2017 , we had the following outstanding interest rate derivatives that were designated as cash flow hedges of interest rate risk: Interest Rate Derivative Number of Instruments Notional Amount Interest Rate Caps 2 $ 50,000,000 Interest Rate Swaps 10 $ 550,000,000
Effect of Derivative Instruments on Consolidated Statement of Operations	Tabular Disclosure of the Effect of Derivative Instruments on the Condensed Consolidated Statements of Operations The table below presents the effect of our derivative financial instruments on the Condensed Consolidated Statements of Operations for the three and nine months ended September 30, 2017 and 2016 (dollars in thousands): Derivatives in Cash Flow Hedging Relationships Amount of Gain or (Loss) Location of Gain or Amount of Gain or (Loss) Location of Gain or Amount of Gain or (Loss) Recognized in Interest Expense (Ineffective Three months ended September 30, 2017 2016 2017 2016 2017 2016 Interest rate contracts $ 90 $ 1,179 Interest Expense $ 33 $ (1,042 ) Interest Expense $ (3 ) $ 96 Nine months ended September 30, Interest rate contracts $ (1,252 ) $ (3,840 ) Interest Expense $ (884 ) $ (3,359 ) Interest Expense $ (17 ) $ (67 ) Derivatives Not Designated as Hedging Instruments Location of Gain Recognized in Income on Derivative Amount of Gain Recognized in Income on Derivative Three months ended September 30, 2017 2016 Preferred stock embedded derivative Interest and other non-property income $ 4,107 $ — Nine months ended September 30, Preferred stock embedded derivative Interest and other non-property income $ 5,827 $ —
Schedule of Accumulated Other Comprehensive Income (Loss) [Table Text Block]	Other Comprehensive Income MAA's other comprehensive income consists entirely of gains and losses attributable to the effective portion of our cash flow hedges. The chart below shows the change in the balance for the nine months ended September 30, 2017 and 2016 (dollars in thousands): Changes in Accumulated Other Comprehensive Income (Loss) by Component Affected Line Item in the Condensed Consolidated Statements Of Operations Gains and Losses on Cash Flow Hedges For the nine months ended September 30, 2017 2016 Beginning balance $ 1,144 $ (1,589 ) Other comprehensive income (loss) before reclassifications (1,252 ) (3,840 ) Amounts reclassified from accumulated other comprehensive income (interest rate contracts) Interest expense 884 3,359 Net current-period other comprehensive loss attributable to noncontrolling interests 14 25 Net current-period other comprehensive loss attributable to MAA (354 ) (456 ) Ending balance $ 790 $ (2,045 )

Fair Value Disclosure of Fina31

Fair Value Disclosure of Financial Instruments (Tables)	9 Months Ended
	Sep. 30, 2017
Notes To Financial Statements [Abstract]
Assets and Liabilities Measured at Fair Value on a Recurring Basis	Assets and Liabilities Measured at Fair Value on a Recurring Basis at December 31, 2016 (dollars in thousands) Balance Sheet Location Quoted Prices in Significant Significant Balance at December 31, 2016 Assets Interest rate derivative contracts Other assets $ — $ 2,364 $ — $ 2,364 Preferred stock embedded derivative Other assets — 10,783 — 10,783 Total $ — $ 13,147 $ — $ 13,147 Liabilities Interest derivative rate contracts Fair market value of interest rate swaps $ — $ 7,562 $ — $ 7,562 September 30, 2017 and December 31, 2016 , aggregated by the level in the fair value hierarchy within which those measurements fall. Assets and Liabilities Measured at Fair Value on a Recurring Basis at September 30, 2017 (dollars in thousands) Balance Sheet Location Quoted Prices in Significant Significant Balance at September 30, 2017 Assets Interest rate derivative contracts Other assets $ — $ 2,043 $ — $ 2,043 Preferred stock embedded derivative Other assets — 18,190 — 18,190 Total $ — $ 20,233 $ — $ 20,233 Liabilities Interest derivative rate contracts Fair market value of interest rate swaps $ — $ 2,602 $ — $ 2,602

Segment Information (Tables)

Segment Information (Tables)	9 Months Ended
	Sep. 30, 2017
Notes To Financial Statements [Abstract]
Revenues and NOI for Reportable Segment	Revenues and NOI for each reportable segment for the three- and nine- month periods ended September 30, 2017 and 2016 were as follows (dollars in thousands): Three months ended September 30, Nine months ended September 30, 2017 2016 2017 2016 Revenues: Large Market Same Store $ 169,105 $ 165,046 $ 503,076 $ 487,725 Secondary Market Same Store 87,895 85,822 261,272 254,685 Non-Same Store and Other 127,550 26,030 381,901 75,740 Total operating revenues $ 384,550 $ 276,898 $ 1,146,249 $ 818,150 NOI: Large Market Same Store $ 104,574 $ 101,595 $ 313,419 $ 302,230 Secondary Market Same Store 53,836 53,124 162,617 159,263 Non-Same Store and Other 76,961 15,533 233,792 46,175 Total NOI 235,371 170,252 709,828 507,668 Depreciation and amortization (117,928 ) (76,959 ) (374,285 ) (227,829 ) Acquisition expenses — (1,033 ) — (2,167 ) Property management expenses (10,281 ) (7,908 ) (32,007 ) (25,221 ) General and administrative expenses (8,361 ) (6,661 ) (30,735 ) (20,257 ) Merger related expenses (128 ) (3,901 ) (3,977 ) (3,901 ) Integration costs (4,002 ) — (10,521 ) — Interest and other non-property income 4,303 64 7,632 159 Interest expense (39,940 ) (32,168 ) (115,005 ) (96,418 ) Gain on debt extinguishment/modification 828 — 3,168 3 Gain on sale of depreciable real estate assets 58,844 47,749 59,045 48,572 Net casualty gain (loss) after insurance and other settlement proceeds 564 (75 ) 233 738 Income tax expense (641 ) (454 ) (1,910 ) (1,200 ) (Loss) gain on sale of non-depreciable real estate assets (6 ) — 42 2,170 Gain from real estate joint ventures 335 — 1,021 27 Net income attributable to noncontrolling interests (4,249 ) (4,627 ) (7,600 ) (9,508 ) Preferred Dividends (922 ) — (2,766 ) — Net income available for MAA common shareholders $ 113,787 $ 84,279 $ 202,163 $ 172,836
Assets for Reportable Segment	Assets for each reportable segment as of September 30, 2017 and December 31, 2016 were as follows (dollars in thousands): September 30, 2017 December 31, 2016 Assets: Large Market Same Store $ 4,038,127 $ 4,126,885 Secondary Market Same Store 1,731,050 1,768,183 Non-Same Store and Other 5,527,583 5,479,780 Corporate assets 236,041 229,643 Total assets $ 11,532,801 $ 11,604,491

Real Estate Acquisitions and 33

Real Estate Acquisitions and Dispositions Real Estate Acquisitions and Dispositions (Tables)	9 Months Ended
	Sep. 30, 2017
Real Estate [Abstract]
Acquisitions and Dispositions [Table Text Block]	The following chart shows our acquisition activity for the nine months ended September 30, 2017 : Community Market Units Date Acquired Charlotte at Midtown Nashville, TN 279 March 16, 2017 The following chart shows our disposition activity for the nine months ended September 30, 2017 : Community Market Units or Acres Date Sold Lakewood Ranch - Outparcel Tampa, FL 12 acres April 7, 2017 Post Alexander - Outparcel Atlanta, GA 1 acre June 12, 2017 Paddock Club Lakeland Lakeland, FL 464 July 13, 2017 Paddock Club Lakeland - Outparcel Lakeland, FL 9 acres July 13, 2017 Paddock Club Montgomery Montgomery, AL 208 July 20, 2017 Northwood Place Fort Worth, TX 270 July 20, 2017 Town Park Lot 12 Orlando, FL 1 acre August 7, 2017

Consolidation and Basis of Pres

Consolidation and Basis of Presentation and Significant Accounting Policies - Additional Information (Detail) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017USD ($)	Sep. 30, 2016USD ($)shares	Sep. 30, 2017USD ($)	Sep. 30, 2016USD ($)shares	Sep. 30, 2017Property	Sep. 30, 2017States	Sep. 30, 2017$ / shares	Sep. 30, 2017Communities	Sep. 30, 2017USD ($)	Sep. 30, 2017shares	Sep. 30, 2017ft²	Dec. 31, 2016USD ($)$ / shares
Real Estate Properties [Line Items]
General Partners' Capital Account, Units Outstanding | shares		75,542,583		75,542,583						113,627,014
Limited Liability (LLC) or Limited Partnership (LP), Managing Member or General Partner, Ownership Interest			96.40%
Preferred Stock, Dividend Rate, Percentage			8.50%
Number of owned or owned interests of apartment communities					303			302
Number of states in which apartment units are located | States						17
Percentage Of Ownership Interests	100.00%		100.00%
Minimum [Member]
Real Estate Properties [Line Items]
Percentage Of Ownership Interests	92.50%		92.50%
Maximum [Member]
Real Estate Properties [Line Items]
Percentage Of Ownership Interests	100.00%		100.00%
Development Properties [Member]
Real Estate Properties [Line Items]
Number of owned or owned interests of apartment communities | Communities								5
Number of units under development community | Property					1,434
Development Properties [Member] | Expected Costs [Member]
Real Estate Properties [Line Items]
Development and capital improvements in progress									$ 305,000
Development Properties [Member] | Costs Incurred to Date [Member]
Real Estate Properties [Line Items]
Development and capital improvements in progress									235,300
Retail
Real Estate Properties [Line Items]
Number of owned or owned interests of apartment communities | Property					29
Square Footage of Real Estate Property | ft²											600,000
Commercial Real Estate [Member]
Real Estate Properties [Line Items]
Square Footage of Real Estate Property | ft²											232,000
Real Estate Technology Ventures, L.P. [Member]
Real Estate Properties [Line Items]
Equity Method Investment, Ownership Percentage	32.00%		32.00%
Real Estate Investments, Joint Ventures									800
Real Estate Technology Ventures, L.P. [Member] | Limited Partner Capital Contribution, Future Obligation [Member]
Real Estate Properties [Line Items]
Real Estate Investments, Joint Ventures									14,200
Post River North [Member]
Real Estate Properties [Line Items]
Number of apartments included in a community	358		358
Development and capital improvements in progress									60,300
Percentage Of Ownership Interests	92.50%		92.50%
Land									14,500
Accrued expenses and other liabilities									6,200
Post Massachusetts Avenue [Member]
Real Estate Properties [Line Items]
Equity Method Investment, Ownership Percentage	35.00%		35.00%
Real Estate Investments, Joint Ventures									45,100
Parent Company [Member]
Real Estate Properties [Line Items]
Preferred Stock, Par or Stated Value Per Share | $ / shares							$ 0.01					$ 0.01
Merger Related Expenses	$ 128	$ 3,901	$ 3,977	$ 3,901
Development and capital improvements in progress									156,938			$ 231,224
Land									1,828,637			1,816,008
Accrued expenses and other liabilities									$ 439,662			$ 414,244

Business Combinations Textual (

Business Combinations Textual (Details)	Dec. 01, 2016USD ($)ft²Communitiesproperties$ / sharesshares	Sep. 30, 2017USD ($)Communitiesshares	Dec. 31, 2016shares
Business Acquisition [Line Items]
Embedded Derivative, Fair Value of Embedded Derivative Asset	$ 10,800,000	$ 18,190,000
Business Combinations, Other Consideration	2,000,000
Preferred Stock, Shares Outstanding | shares		867,846
Business Combination, Separately Recognized Transactions [Domain]
Business Acquisition [Line Items]
Business Combination, Merger and Integration Related Expenses		$ 14,500,000
Unsecured Debt [Member]
Business Acquisition [Line Items]
Business Combination, Consideration Transferred, Other	300,000,000
Redeemable Preferred Stock [Member]
Business Acquisition [Line Items]
Mandatorily Redeemable Preferred Stock, Fair Value Disclosure	77
Embedded Derivative, Fair Value of Embedded Derivative Asset	$ 14.24
Preferred Stock, Shares Outstanding | shares	867,846
Line of Credit [Member]
Business Acquisition [Line Items]
Business Combination, Consideration Transferred, Other	$ 162,000,000
Parent Company [Member]
Business Acquisition [Line Items]
Preferred Stock, Shares Outstanding | shares		867,846	867,846
Parent Company [Member] | Post [Member] [Domain]
Business Acquisition [Line Items]
Number of Apartment Communities Acquired in Real Estate Property | Communities	61
Number Of Units Acquired In Real Estate Property | Communities	24,138
Number of Commercial Properties Acquired in Real Estate Property | properties	4
Business Acquisition, Cost of Entity Acquired, Purchase Price	$ 4,000,000,000
Share Price | $ / shares	$ 91.41
Stock Issued During Period, Shares, Acquisitions | shares	38,000,000
Equity Method Investments [Member] | Post [Member] [Domain]
Business Acquisition [Line Items]
Number Of Units Acquired In Real Estate Property | Communities	269
Development Portfolio [Member] | Post [Member] [Domain]
Business Acquisition [Line Items]
Number Of Units Acquired In Real Estate Property | Communities	2,262
Commercial [Member] | Parent Company [Member] | Post [Member] [Domain]
Business Acquisition [Line Items]
Square Footage of Real Estate Property | ft²	232,000
Noncontrolling Interest [Member]
Business Acquisition [Line Items]
Stock Issued During Period, Shares, Acquisitions | shares	80,000
Post Massachusetts Avenue [Member]
Business Acquisition [Line Items]
Number of Apartment Communities Acquired in Real Estate Property | Communities		1

Business Combinations (Unaudite

Business Combinations (Unaudited Pro forma Information) (Details) - Parent Company [Member] - Post [Member] [Domain] $ in Thousands	Dec. 01, 2016USD ($)
Business Acquisition [Line Items]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Assets	$ 4,742,900
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Liabilities	732,001
Business Acquisition, Cost of Entity Acquired, Purchase Price	4,000,000
Land [Member]
Business Acquisition [Line Items]
Business Acquisition, PPA, Assets Acquired	875,294
Building and Building Improvements [Member]
Business Acquisition [Line Items]
Business Acquisition, PPA, Assets Acquired	3,397,342
Furniture Fixtures And Equipment [Member]
Business Acquisition [Line Items]
Business Acquisition, PPA, Assets Acquired	81,243
Construction in Progress [Member]
Business Acquisition [Line Items]
Business Acquisition, PPA, Assets Acquired	183,881
Unimproved Land [Member]
Business Acquisition [Line Items]
Business Acquisition, PPA, Assets Acquired	24,200
Disposal Group, Held-for-sale, Not Discontinued Operations [Member]
Business Acquisition [Line Items]
Business Acquisition, PPA, Assets Acquired	3,610
Real Estate Investment [Member]
Business Acquisition [Line Items]
Business Acquisition, PPA, Assets Acquired	44,435
Finite-Lived Intangible Assets, Major Class Name [Domain]
Business Acquisition [Line Items]
Business Acquisition, PPA, Assets Acquired	53,192
Cash and Cash Equivalents [Member]
Business Acquisition [Line Items]
Business Acquisition, PPA, Assets Acquired	34,292
Restricted Cash [Member]
Business Acquisition [Line Items]
Business Acquisition, PPA, Assets Acquired	3,608
Other Assets [Member]
Business Acquisition [Line Items]
Business Acquisition, PPA, Assets Acquired	41,803
Debt [Member]
Business Acquisition [Line Items]
Business Acquisition, PPA, Liabilities Assumed	(595,609)
Interest Rate Cash Flow Hedge Liability at Fair Value [Domain]
Business Acquisition [Line Items]
Business Acquisition, PPA, Liabilities Assumed	(2,118)
Other Current Liabilities [Member]
Business Acquisition [Line Items]
Business Acquisition, PPA, Assets Acquired	(1,661)
Other Liabilities [Member]
Business Acquisition [Line Items]
Business Acquisition, PPA, Liabilities Assumed	(132,613)
Noncontrolling Interest [Member]
Business Acquisition [Line Items]
Business Acquisition, PPA, Liabilities Assumed	$ (2,306)

Earnings Per Common Share of 37

Earnings Per Common Share of MAA Earnings Per Common Share of MAA (Details) - Parent Company [Member] - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Earnings Per Share Disclosure [Line Items]
Weighted average common shares - basic		113,434	75,302	113,392	75,276
Weighted average partnership units outstanding	[1]	0	0	0	4,156
Effect of dilutive securities	[2]	219	0	270	246
Weighted average common shares - diluted		113,653	75,302	113,662	79,678
Dividends, Preferred Stock, Cash				$ 2,766	$ 0
Calculation of Basic Earnings per Share [Member]
Earnings Per Share Disclosure [Line Items]
Income from continuing operations		$ 118,958	$ 88,906	212,529	182,344
Income from continuing operations attributable to noncontrolling interests		(4,249)	(4,627)	(7,600)	(9,508)
Income from continuing operations allocated to unvested restricted shares		(181)	(254)	(337)	(485)
Dividends, Preferred Stock, Cash		(922)	0	(2,766)	0
Income from continuing operations available for common shareholders, adjusted		$ 113,606	$ 84,025	$ 201,826	$ 172,351
Earnings per share - basic		$ 1	$ 1.12	$ 1.78	$ 2.29
Calculation of Diluted Earnings per Share [Member]
Earnings Per Share Disclosure [Line Items]
Income from continuing operations		$ 118,958	$ 88,906	$ 212,529	$ 182,344
Income from continuing operations attributable to noncontrolling interests	[1]	(4,249)	(4,628)	(7,600)	0
Income from continuing operations allocated to unvested restricted shares	[2]	0	(254)	0	0
Dividends, Preferred Stock, Cash		(922)		(2,766)	0
Income from continuing operations available for common shareholders, adjusted		$ 113,787	$ 84,024	$ 202,163	$ 182,344
Earnings per share - diluted		$ 1	$ 1.12	$ 1.78	$ 2.29
Limited Partnership Units [Member]
Earnings Per Share Disclosure [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount				4,200
Restricted Stock [Member]
Earnings Per Share Disclosure [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount			200
[1]	(1) For both the three and nine months ended September 30, 2017 and the three months ended September 30, 2016, 4.2 million OP Units and their related income are not included in the diluted earnings per share calculations as they are not dilutive.
[2]	(2) For the three months ended September 30, 2016, 0.2 million potentially dilutive securities and their related income are not included in the diluted earnings per share calculations as they are not dilutive.

Earnings Per OP Unit of MAALP E

Earnings Per OP Unit of MAALP Earnings Per OP Unit of MAALP (Details) - Limited Partner [Member] - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Earnings Per Share Disclosure [Line Items]
Weighted average common units - basic	117,643	79,449	117,607	79,432
Effect of dilutive securities	219	0	270	246
Weighted average common shares - diluted	117,862	79,449	117,877	79,678
Dividends, Preferred Stock, Cash			$ 2,766	$ 0
Calculation of Basic Earnings Per Unit [Member]
Earnings Per Share Disclosure [Line Items]
Income from continuing operations	$ 118,958	$ 88,906	212,529	182,344
Income from continuing operations allocated to unvested restricted shares	(181)	(254)	(337)	(484)
Dividends, Preferred Stock, Cash	(922)	0	(2,766)	0
Income from continuing operations available for common unitholders, adjusted	$ 117,855	$ 88,652	$ 209,426	$ 181,860
Earnings per unit - basic	$ 1	$ 1.12	$ 1.78	$ 2.29
Calculation of Diluted Earnings Per Unit [Member]
Earnings Per Share Disclosure [Line Items]
Income from continuing operations	$ 118,958	$ 88,906	$ 212,529	$ 182,344
Income from continuing operations allocated to unvested restricted shares	0	(254)	0	0
Dividends, Preferred Stock, Cash	(922)	0	(2,766)	0
Income from continuing operations available for common unitholders, adjusted	$ 118,036	$ 88,652	$ 209,763	$ 182,344
Earnings per unit - diluted	$ 1	$ 1.12	$ 1.78	$ 2.29
Restricted Stock [Member]
Earnings Per Share Disclosure [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount		200

MAA Equity (Details)

MAA Equity (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Accumulated Distributions in Excess of Net Income [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance				$ (634,141,000)
Net income attributable to MAA				172,836,000
Redeemable stock fair market value				(296,000)
Dividends on common stock				(185,789,000)
Ending Balance		$ (647,390,000)		(647,390,000)
Common Stock [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance				753,000
Issuance and registration of common shares				1,000
Shares repurchased and retired				0
Shares issued in exchange for units				0
Ending Balance		754,000		754,000
Additional Paid-in Capital [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance				3,627,074,000
Issuance and registration of common shares				(739,000)
Shares repurchased and retired				(1,811,000)
Shares issued in exchange for units				780,000
Shares issued in exchange for redeemable stock				122,000
Adjustment for noncontrolling interest ownership in operating partnership				(38,000)
Amortization of unearned compensation				6,625,000
Ending Balance		3,632,013,000		3,632,013,000
Noncontrolling Interest [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance				165,726,000
Net Income Attributable to Noncontrolling Interest				9,508,000
Other comprehensive (loss) income - derivatives insturments (cash flow hedges)				(25,000)
Shares issued in exchange for units				(780,000)
Adjustment for noncontrolling interest ownership in operating partnership				38,000
Dividends on common stock				0
Dividends on noncontrolling interest units				(10,217,000)
Ending Balance		164,250,000		164,250,000
Accumulated Other Comprehensive Income (Loss) [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance				(1,589,000)
Other comprehensive (loss) income - derivatives insturments (cash flow hedges)				(456,000)
Ending Balance		(2,045,000)		(2,045,000)
Parent Company [Member]
Equity [Line Items]
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	$ 118,958,000	$ 88,906,000	$ 212,529,000	$ 182,344,000
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	6,548,320,000		6,548,320,000		$ 6,639,795,000
Noncontrolling Interest in Joint Ventures	$ 2,306,000		$ 2,306,000		2,306,000
Common Stock, Dividends, Per Share, Declared	$ 0.87	$ 0.82	$ 2.61	$ 2.46
Distribution Made to Limited Partner, Distributions Declared, Per Unit			$ 2.61	$ 2.46
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance and registration of common shares			$ 2,007,000
Proceeds from Issuance of Common Stock			1,007,000	$ (216,000)
Dividends, Preferred Stock, Cash			(2,766,000)	0
Parent Company [Member] | Accumulated Distributions in Excess of Net Income [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance			(707,479,000)
Net income attributable to MAA			204,929,000
Other comprehensive (loss) income - derivatives insturments (cash flow hedges)			0
Issuance and registration of common shares			0
Shares repurchased and retired			0
Stock Issued During Period, Value, Stock Options Exercised			0
Shares issued in exchange for units			0
Redeemable stock fair market value			(870,000)
Adjustment for noncontrolling interest ownership in operating partnership			0
Amortization of unearned compensation			(114,000)
Dividends, Preferred Stock, Cash			(2,766,000)
Dividends on common stock			(296,535,000)
Dividends on noncontrolling interest units			0
Ending Balance	$ (802,835,000)		(802,835,000)
Parent Company [Member] | Preferred Stock [Member]
Equity [Line Items]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	9,000		9,000		$ 9,000
Parent Company [Member] | Common Stock [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance			1,133,000
Issuance and registration of common shares			1,000
Shares repurchased and retired			0
Stock Issued During Period, Value, Stock Options Exercised			0
Shares issued in exchange for units			0
Ending Balance	1,134,000		1,134,000
Parent Company [Member] | Additional Paid-in Capital [Member]
Equity [Line Items]
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest			0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance			7,109,012,000
Other comprehensive (loss) income - derivatives insturments (cash flow hedges)			0
Issuance and registration of common shares			2,007,000
Proceeds from Issuance of Common Stock			153,000
Shares repurchased and retired			(4,782,000)
Stock Issued During Period, Value, Stock Options Exercised			218,000
Shares issued in exchange for units			1,133,000
Shares issued in exchange for redeemable stock			1,482,000
Redeemable stock fair market value			0
Adjustment for noncontrolling interest ownership in operating partnership			54,000
Amortization of unearned compensation			8,552,000
Dividends on common stock			0
Dividends on noncontrolling interest units			0
Ending Balance	7,117,829,000		7,117,829,000
Parent Company [Member] | Noncontrolling Interest [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance			235,976,000
Net Income Attributable to Noncontrolling Interest			7,600,000
Other comprehensive (loss) income - derivatives insturments (cash flow hedges)			(14,000)
Issuance and registration of common shares			0	0
Shares repurchased and retired			0
Stock Issued During Period, Value, Stock Options Exercised			0
Shares issued in exchange for units			(1,133,000)
Redeemable stock fair market value			0
Adjustment for noncontrolling interest ownership in operating partnership			(54,000)
Amortization of unearned compensation			0
Dividends on common stock			0
Dividends on noncontrolling interest units			(10,982,000)
Ending Balance	231,393,000		231,393,000
Parent Company [Member] | Accumulated Other Comprehensive Income (Loss) [Member]
Equity [Line Items]
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest			0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance			1,144,000
Other comprehensive (loss) income - derivatives insturments (cash flow hedges)			(354,000)
Issuance and registration of common shares			0
Shares repurchased and retired			0
Stock Issued During Period, Value, Stock Options Exercised			0
Shares issued in exchange for units			0
Redeemable stock fair market value			0
Adjustment for noncontrolling interest ownership in operating partnership			0
Amortization of unearned compensation			0
Dividends on common stock			0
Dividends on noncontrolling interest units			0
Ending Balance	790,000		790,000
Stockholders' Equity, Total [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance				3,157,823,000
Net Income Including Portion Attributable to Noncontrolling Interest				182,344,000
Other comprehensive (loss) income - derivatives insturments (cash flow hedges)				(481,000)
Issuance and registration of common shares				(738,000)
Shares repurchased and retired				(1,811,000)
Shares issued in exchange for units				0
Shares issued in exchange for redeemable stock				122,000
Redeemable stock fair market value				(296,000)
Adjustment for noncontrolling interest ownership in operating partnership				0
Amortization of unearned compensation				6,625,000
Dividends on common stock				(185,789,000)
Dividends on noncontrolling interest units				(10,217,000)
Ending Balance		$ 3,147,582,000		$ 3,147,582,000
Stockholders' Equity, Total [Member] | Parent Company [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance			6,642,101,000
Net Income Including Portion Attributable to Noncontrolling Interest			212,529,000
Other comprehensive (loss) income - derivatives insturments (cash flow hedges)			(368,000)
Issuance and registration of common shares			154,000
Shares repurchased and retired			(4,782,000)
Stock Issued During Period, Value, Stock Options Exercised			218,000
Shares issued in exchange for units			0
Shares issued in exchange for redeemable stock			1,482,000
Redeemable stock fair market value			(870,000)
Adjustment for noncontrolling interest ownership in operating partnership			0
Amortization of unearned compensation			8,438,000
Dividends on common stock			(296,535,000)
Dividends on noncontrolling interest units			(10,982,000)
Ending Balance	$ 6,550,626,000		$ 6,550,626,000

MAALP Capital (Details)

MAALP Capital (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
General Partners' Capital Account [Member]
Increase (Decrease) in Partners' Capital [Roll Forward]
Units Issued During Period, Value, Unit Options Exercised			$ 218
Total Partnership Capital [Member]
Increase (Decrease) in Partners' Capital [Roll Forward]
Units Issued During Period, Value, Unit Options Exercised			218
Limited Partner [Member]
Capital Disclosure [Line Items]
Noncontrolling Interest in Joint Ventures	$ 2,306		$ 2,306		$ 2,306
Distribution Made to Limited Partner, Distributions Declared, Per Unit	$ 0.87	$ 0.82	$ 2.61	$ 2.46
Increase (Decrease) in Partners' Capital [Roll Forward]
Dividends, Preferred Stock, Cash			$ 2,766	$ 0
Limited Partner [Member] | General Partners' Capital Account [Member]
Increase (Decrease) in Partners' Capital [Roll Forward]
Beginning Balance			6,337,721	2,993,696	2,993,696
Net Income Allocated to General Partners			202,163	172,836
Issuance of units			154	(738)
Units repurchased and retired			(4,782)	(1,811)
General partner units issued in exchange for limited partner units			1,133	780
Units issued in exchange for redeemable units			1,482	122
Redeemable stock fair market value			(870)	(296)
Adjustment for noncontrolling interest ownership in operating partnership			68	(13)
Amortization of unearned compensation			8,438	6,625
Distributions			(296,535)	(185,789)
Ending Balance	$ 6,249,190	$ 2,985,412	6,249,190	2,985,412	6,337,721
Limited Partner [Member] | Total Partnership Capital [Member]
Increase (Decrease) in Partners' Capital [Roll Forward]
Beginning Balance			6,642,082	3,157,804	3,157,804
Net Income Available for Common Unitholders			212,529	182,344
Other comprehensive (loss) income - derivatives insturments (cash flow hedges)			(368)	(481)
Issuance of units			2,161	(738)
Units repurchased and retired			(4,782)	(1,811)
General partner units issued in exchange for limited partner units			0	0
Units issued in exchange for redeemable units			1,482	122
Redeemable stock fair market value			(870)	(296)
Adjustment for noncontrolling interest ownership in operating partnership			0	0
Amortization of unearned compensation			8,438	6,625
Distributions			(307,517)	(196,006)
Dividends, Preferred Stock, Cash			2,766
Ending Balance	6,550,607	3,147,563	6,550,607	3,147,563	6,642,082
Limited Partner [Member] | Limited Partner [Member]
Increase (Decrease) in Partners' Capital [Roll Forward]
Beginning Balance			235,976	165,726	165,726
Net Income Allocated to Limited Partners			7,600	9,508
General partner units issued in exchange for limited partner units			(1,133)	(780)
Adjustment for noncontrolling interest ownership in operating partnership			(68)	13
Distributions			(10,982)	(10,217)
Ending Balance	231,393	164,250	231,393	164,250	235,976
Limited Partner [Member] | AOCI Attributable to Noncontrolling Interest [Member]
Increase (Decrease) in Partners' Capital [Roll Forward]
Beginning Balance			1,246	(1,618)	(1,618)
Other comprehensive (loss) income - derivatives insturments (cash flow hedges)			(368)	(481)
Ending Balance	878	$ (2,099)	878	(2,099)	1,246
Accumulated Distributions in Excess of Net Income [Member]
Increase (Decrease) in Partners' Capital [Roll Forward]
Redeemable stock fair market value				$ (296)
Accumulated Distributions in Excess of Net Income [Member] | Limited Partner [Member]
Increase (Decrease) in Partners' Capital [Roll Forward]
Issuance of units			2,007		$ 64,833
Dividends, Preferred Stock, Cash			2,766
Preferred Stock Including Additional Paid in Capital [Member] | Limited Partner [Member]
Increase (Decrease) in Partners' Capital [Roll Forward]
Ending Balance	$ 66,840		$ 66,840

Borrowings - Additional Informa

Borrowings - Additional Information (Detail) $ in Thousands	9 Months Ended
	Sep. 30, 2017USD ($)
Debt Instrument [Line Items]
Notes Payable	$ 4,492,834
Debt Instrument, Interest Rate, Effective Percentage	3.50%
Debt Instrument, Maturity Date	Feb. 13, 2022
Conventional Variable Rate Debt [Member]
Debt Instrument [Line Items]
Long-term Debt, Percentage Bearing Variable Interest, Percentage Rate	1.70%
Long-term Debt	$ 110,000
Capped Conventional Variable Rate Debt [Member]
Debt Instrument [Line Items]
Long-term Debt, Percentage Bearing Variable Interest, Percentage Rate	1.70%
Long-term Debt	$ 50,000
Variable Rate Debt [Member]
Debt Instrument [Line Items]
Unsecured notes payable	$ 300,000
Debt Instrument, Interest Rate, Effective Percentage	2.20%
Debt Instrument, Maturity Date	Aug. 29, 2020
Mortgages [Member]
Debt Instrument [Line Items]
Mortgage Loans on Real Estate	$ 9,000
Repayments of Debt	156,400
Other Than Conventional Variable Rate Debt [Member]
Debt Instrument [Line Items]
Long-term Debt	$ 950,000
Debt Instrument Average Interest Rate	4.00%
Fixed Rate Senior Notes [Member]
Debt Instrument [Line Items]
Unsecured notes payable	$ 2,800,000
Long-term Debt, Percentage Bearing Fixed Interest, Percentage Rate	3.80%
Secured Debt [Member]
Debt Instrument [Line Items]
Notes Payable	$ 1,109,973
Debt Instrument, Interest Rate, Effective Percentage	3.60%
Debt Instrument, Maturity Date	Jul. 3, 2019
Secured Debt [Member] | Federal National Mortgage Association Certificates and Obligations (FNMA) [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Amount Outstanding	$ 160,000
Line of Credit Facility, Maximum Borrowing Capacity	$ 160,000
Secured Debt [Member] | Federal National Mortgage Association Certificates and Obligations (FNMA) [Member] | Variable Rate Debt [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Effective Percentage	1.70%
Secured Debt [Member] | Mortgages [Member] | Fixed Rate Debt
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Effective Percentage	4.00%
Debt Instrument, Maturity Date	Sep. 11, 2019
Mortgage Loans on Real Estate	$ 933,256
Unsecured Debt [Member]
Debt Instrument [Line Items]
Notes Payable	$ 3,382,861
Debt Instrument, Interest Rate, Effective Percentage	3.50%
Debt Instrument, Maturity Date	Jan. 18, 2023
Unsecured Debt [Member] | Wells Fargo Term Loan [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount	$ 300,000
Unsecured Debt [Member] | US Bank Term Loan [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount	$ 150,000
Unsecured Debt [Member] | $1 billion unsecured revolving credit faciltiy [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Effective Percentage	2.14%
Letters of Credit Outstanding, Amount	$ 2,500
Unsecured Debt [Member] | $1 billion unsecured revolving credit faciltiy [Member] | Variable Rate Debt [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Effective Percentage	2.10%
Debt Instrument, Maturity Date	Apr. 15, 2020
Line of Credit Facility, Amount Outstanding	$ 250,000
Unsecured Debt [Member] | KeyBank Term Loan [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount	150,000
Unsecured Debt [Member] | Public Income Notes [Member] | Fixed Rate Debt
Debt Instrument [Line Items]
Debt Instrument, Face Amount	2,000,000
Unsecured Debt [Member] | Private Placement [Member] | Fixed Rate Debt
Debt Instrument [Line Items]
Debt Instrument, Face Amount	310,000
Unsecured Debt [Member] | 3.6% Notes due 2027 [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount	$ 600,000
Debt Instrument, Interest Rate, Effective Percentage	3.68%
Debt Instrument, Unamortized Discount, Current	$ 2,500
Other Underwriting Expense	$ 3,900
Debt Instrument, Issue Price	99.58%
Settlement of Forward Swaps	$ 300,000
Debt Instrument, Interest Rate, Stated Percentage	3.60%
Proceeds from Unsecured Notes Payable	$ 593,600
Unsecured Debt [Member] | 2011 and 2012 Senior Notes [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount	310,000
Unsecured Debt [Member] | $1 billion unsecured revolving credit facility [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Amount Outstanding	250,000
Line of Credit Facility, Maximum Borrowing Capacity	1,000,000
Unsecured Debt [Member] | Term Loan [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount	$ 550,000
Debt Instrument, Interest Rate, Effective Percentage	3.00%
Debt Instrument, Maturity Date	Apr. 17, 2018
Minimum [Member] | Unsecured Debt [Member] | Fixed Rate Debt
Debt Instrument [Line Items]
Debt Instrument, Term	5 years
Minimum [Member] | Unsecured Debt [Member] | Wells Fargo Term Loan [Member]
Debt Instrument [Line Items]
Debt Instrument, Basis Spread on Variable Rate	0.90%
Minimum [Member] | Unsecured Debt [Member] | $1 billion unsecured revolving credit faciltiy [Member]
Debt Instrument [Line Items]
Debt Instrument, Basis Spread on Variable Rate	0.85%
Minimum [Member] | Unsecured Debt [Member] | KeyBank Term Loan [Member]
Debt Instrument [Line Items]
Debt Instrument, Basis Spread on Variable Rate	0.90%
Minimum [Member] | Unsecured Debt [Member] | Wells Fargo and US Bank Term Loans [Member]
Debt Instrument [Line Items]
Debt Instrument, Basis Spread on Variable Rate	0.90%
Minimum [Member] | Unsecured Debt [Member] | Term Loan [Member]
Debt Instrument [Line Items]
Debt Instrument, Basis Spread on Variable Rate	0.90%
Maximum [Member] | Unsecured Debt [Member] | Fixed Rate Debt
Debt Instrument [Line Items]
Debt Instrument, Term	12 years
Maximum [Member] | Unsecured Debt [Member] | Wells Fargo Term Loan [Member]
Debt Instrument [Line Items]
Debt Instrument, Basis Spread on Variable Rate	1.90%
Maximum [Member] | Unsecured Debt [Member] | $1 billion unsecured revolving credit faciltiy [Member]
Debt Instrument [Line Items]
Debt Instrument, Basis Spread on Variable Rate	1.55%
Line of Credit Facility, Maximum Borrowing Capacity	$ 1,500,000
Maximum [Member] | Unsecured Debt [Member] | KeyBank Term Loan [Member]
Debt Instrument [Line Items]
Debt Instrument, Basis Spread on Variable Rate	1.75%
Maximum [Member] | Unsecured Debt [Member] | Wells Fargo and US Bank Term Loans [Member]
Debt Instrument [Line Items]
Debt Instrument, Basis Spread on Variable Rate	1.90%
Maximum [Member] | Unsecured Debt [Member] | Term Loan [Member]
Debt Instrument [Line Items]
Debt Instrument, Basis Spread on Variable Rate	1.75%
years to maturity [Member] | Unsecured Debt [Member] | Fixed Rate Debt
Debt Instrument [Line Items]
Debt Instrument, Term	7 years 1 month 6 days

Debt Structure (Details)

Debt Structure (Details)	9 Months Ended
	Sep. 30, 2017USD ($)
Debt Instrument [Line Items]
Total Outstanding Debt	$ 4,492,834,000
Debt Instrument, Interest Rate, Effective Percentage	3.50%
Contract Maturity	Feb. 13, 2022
Variable Rate Debt [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Effective Percentage	2.20%
Contract Maturity	Aug. 29, 2020
Unsecured Debt	$ 300,000,000
Mortgages [Member]
Debt Instrument [Line Items]
Mortgage Loans on Real Estate	9,000,000
Secured Debt [Member]
Debt Instrument [Line Items]
Total Outstanding Debt	$ 1,109,973,000
Debt Instrument, Interest Rate, Effective Percentage	3.60%
Contract Maturity	Jul. 3, 2019
Secured Debt [Member] | Mortgages [Member] | Fixed Rate Debt
Debt Instrument [Line Items]
Mortgage Loans on Real Estate	$ 933,256,000
Debt Instrument, Interest Rate, Effective Percentage	4.00%
Contract Maturity	Sep. 11, 2019
Secured Debt [Member] | Federal National Mortgage Association Certificates and Obligations (FNMA) [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Amount Outstanding	$ 160,000,000
Secured Debt [Member] | Federal National Mortgage Association Certificates and Obligations (FNMA) [Member] | Variable Rate Credit Facility [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Effective Percentage	1.70%
Contract Maturity	Jun. 1, 2018
Line of Credit Facility, Amount Outstanding	$ 160,000,000
Secured Debt [Member] | Federal National Mortgage Association Certificates and Obligations (FNMA) [Member] | Variable Rate Debt [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Effective Percentage	1.70%
Secured Debt [Member] | $1 billion unsecured revolving credit facility [Member] | Fair Market Value Adjustment and Debt Issuance Cost [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Amount Outstanding	$ 16,717,000
Unsecured Debt [Member]
Debt Instrument [Line Items]
Total Outstanding Debt	$ 3,382,861,000
Debt Instrument, Interest Rate, Effective Percentage	3.50%
Contract Maturity	Jan. 18, 2023
Unsecured Debt [Member] | 3.6% Notes due 2027 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Effective Percentage	3.68%
Debt Instrument, Face Amount	$ 600,000,000
Settlement of Forward Swaps	300,000,000
Unsecured Debt [Member] | Wells Fargo Term Loan 2018 [Domain]
Debt Instrument [Line Items]
Debt Instrument, Face Amount	250,000,000
Unsecured Debt [Member] | Wells Fargo Term Loan [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount	$ 300,000,000
Unsecured Debt [Member] | Term Loan [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Effective Percentage	3.00%
Contract Maturity	Apr. 17, 2018
Debt Instrument, Face Amount	$ 550,000,000
Unsecured Debt [Member] | Senior Notes [Member] | Fixed Rate Debt
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Effective Percentage	4.00%
Contract Maturity	Oct. 24, 2024
Debt Instrument, Face Amount	$ 2,310,000,000
Unsecured Debt [Member] | $1 billion unsecured revolving credit facility [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Amount Outstanding	250,000,000
Unsecured Debt [Member] | $1 billion unsecured revolving credit facility [Member] | Fair Market Value Adjustment and Debt Issuance Cost [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount	$ (27,139,000)
Maximum [Member] | Unsecured Debt [Member] | Wells Fargo Term Loan [Member]
Debt Instrument [Line Items]
Debt Instrument, Basis Spread on Variable Rate	1.90%
Maximum [Member] | Unsecured Debt [Member] | Term Loan [Member]
Debt Instrument [Line Items]
Debt Instrument, Basis Spread on Variable Rate	1.75%
Minimum [Member] | Unsecured Debt [Member] | Wells Fargo Term Loan [Member]
Debt Instrument [Line Items]
Debt Instrument, Basis Spread on Variable Rate	0.90%
Minimum [Member] | Unsecured Debt [Member] | Term Loan [Member]
Debt Instrument [Line Items]
Debt Instrument, Basis Spread on Variable Rate	0.90%
Venue at Stonebridge Ranch [Member] | Mortgages [Member]
Debt Instrument [Line Items]
Mortgage Loans on Real Estate	$ 13,900,000
Grand Cypress [Member] | Mortgages [Member]
Debt Instrument [Line Items]
Mortgage Loans on Real Estate	$ 15,800,000

Derivatives and Hedging Activ43

Derivatives and Hedging Activities - Additional Information (Detail)	9 Months Ended
	Sep. 30, 2017USD ($)Contract$ / sharesshares	Dec. 31, 2016USD ($)shares	Dec. 01, 2016USD ($)
Derivative [Line Items]
Embedded Derivative, Fair Value of Embedded Derivative Asset	$ 18,190,000		$ 10,800,000
Business Acquisitions, Purchase Price Allocation, Subsequent Years, Remaining Adjustments	$ 1,600,000
Preferred Stock, Shares Issued | shares	867,846
Preferred Stock, Redemption Price Per Share | $ / shares	$ 50
Embedded Derivative, Gain (Loss) on Embedded Derivative, Net	$ 5,800,000
Credit Default Option [Member]
Derivative [Line Items]
Credit Risk Related Contingent Features Termination Value	2,800,000
Net Liability Position [Member]
Derivative [Line Items]
Credit Risk Related Contingent Features Termination Value	2,800,000
ERROR in label resolution.
Derivative [Line Items]
Fair Value of Credit Risk Derivatives	$ 2,600,000
Designated as Hedging Instrument [Member] | Interest Rate Caps
Derivative [Line Items]
Derivative, Number of Instruments Held | Contract	2
Derivative, Notional Amount	$ 50,000,000
Designated as Hedging Instrument [Member] | Interest Rate Swap [Member]
Derivative [Line Items]
Derivative, Number of Instruments Held | Contract	10
Derivative, Notional Amount	$ 550,000,000
Designated as Hedging Instrument [Member] | Interest Expense
Derivative [Line Items]
Change in fair value of interest rate derivatives included in AOCI and expected to be reclassified in the next 12 months	(80,500)
Other Assets [Member]
Derivative [Line Items]
Interest Rate Cash Flow Hedge Asset at Fair Value	2,000,000	$ 2,400,000
Interest Rate Swap [Member]
Derivative [Line Items]
Fair market value of interest rate swaps	7,600,000	$ 2,600,000
Changes Measurement [Member]
Derivative [Line Items]
Embedded Derivative, Fair Value of Embedded Derivative Asset	$ 7,400,000
Parent Company [Member]
Derivative [Line Items]
Preferred Stock, Shares Issued | shares	867,846	867,846
Interest Rate Cash Flow Hedge Asset at Fair Value	$ 2,000,000	$ 2,400,000
Fair market value of interest rate swaps	$ 2,602,000	$ 7,562,000

Fair Values of Derivative Instr

Fair Values of Derivative Instruments on Condensed Consolidated Balance Sheet (Detail) - USD ($)	Sep. 30, 2017	Dec. 31, 2016
Interest Rate Swap [Member]
Derivatives, Fair Value [Line Items]
Derivative financial instruments, Liability	$ 7,600,000	$ 2,600,000
Parent Company [Member]
Derivatives, Fair Value [Line Items]
Asset Derivatives, Fair Value	2,000,000	2,400,000
Derivative financial instruments, Liability	$ 2,602,000	$ 7,562,000

Effect of Derivative Instrument

Effect of Derivative Instruments on Consolidated Statement of Operations (Detail) - Designated as Hedging Instrument [Member] - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Interest Expense
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Loss Reclassified from Accumulated OCI into Income (Effective Portion)	$ 33	$ (1,042)	$ 884	$ 3,359
(Loss) Gain on Cash Flow Hedge Ineffectiveness, Net	(3)	96	(17)	(67)
Interest rate contracts
Derivative Instruments, Gain (Loss) [Line Items]
Amount of (Loss) or Gain Recognized in OCI on Derivative (Effective Portion)	90	1,179	(1,252)	(3,840)
Embedded Derivative Financial Instruments [Member]
Derivative Instruments, Gain (Loss) [Line Items]
(Loss) Gain on Cash Flow Hedge Ineffectiveness, Net	$ 4,107	$ 0	$ 5,827	$ 0

Derivatives and Hedging Activ46

Derivatives and Hedging Activities Other Comprehensive Income (Details) - Parent Company [Member] - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance			$ 1,144	$ (1,589)
Amount of (Loss) or Gain Recognized in OCI on Derivative (Effective Portion)			(1,252)	(3,840)
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, Net of Tax	$ (33)	$ 1,042	884	3,359
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Noncontrolling Interest			14	25
Other Comprehensive (Loss) Income , Net of Tax, Portion Attributable to Parent			(354)	(456)
Ending Balance	$ 790	$ (2,045)	$ 790	$ (2,045)

Fair Value Disclosure of Fina47

Fair Value Disclosure of Financial Instruments - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Millions	9 Months Ended
	Sep. 30, 2017	Dec. 31, 2016
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Preferred Stock, Redemption Price Per Share	$ 50
Fixed Rate Debt
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Notes Payable, fair value	$ 3,410	$ 3,130
Notes Payable Excluding Interest Rate Swaps and Cap Agreements	3,230	3,000
Variable Rate Debt
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Notes Payable, fair value	1,300	1,500
Notes Payable Excluding Interest Rate Swaps and Cap Agreements	$ 1,300	$ 1,500
Maximum [Member] | Conventional Variable Rate Debt [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt Renewal Period	90 days
Minimum [Member] | Conventional Variable Rate Debt [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt Renewal Period	30 days

Assets and Liabilities Measured

Assets and Liabilities Measured at Fair Value on a Recurring Basis (Detail) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016	Dec. 01, 2016
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Embedded Derivative, Fair Value of Embedded Derivative Asset	$ 18,190		$ 10,800
Fair Value, Measurements, Recurring
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative financial instruments - assets	2,043
Embedded Derivative, Fair Value of Embedded Derivative Asset	18,190	$ 10,783
Derivative financial instruments - liabilities	2,602
Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative financial instruments - assets	0	0
Embedded Derivative, Fair Value of Embedded Derivative Asset	0	0
Derivative financial instruments - liabilities	0	0
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative financial instruments - assets	2,043	2,364
Embedded Derivative, Fair Value of Embedded Derivative Asset	18,190	10,783
Derivative financial instruments - liabilities	2,602	7,562
Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative financial instruments - assets	0	0
Embedded Derivative, Fair Value of Embedded Derivative Asset	0	0
Derivative financial instruments - liabilities	$ 0	$ 0

Shareholders' Equity of MAA - A

Shareholders' Equity of MAA - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Preferred Stock, Shares Outstanding	867,846
Preferred Stock, Liquidation Preference Per Share	$ 50
Preferred Stock, Redemption Date	Oct. 1, 2026
Preferred Stock, Redemption Price Per Share	$ 50
Common stock, shares outstanding	113,627,014	75,542,583
Total common shares and operating partnership units outstanding	117,827,046	79,685,786
Treasury Stock, Shares, Acquired	47,956	19,727
Preferred Stock, Dividend Rate, Percentage	8.50%
Preferred Stock, Dividend Rate, Per-Dollar-Amount	$ 4.25
Preferred Stock, Liquidation Preference, Value	$ 43,400
Equity Option [Member]
Stock Issued During Period, Shares, New Issues	10,340	0
Noncontrolling Interest [Member]
Common Shares Issuable Upon Conversion Of Convertible Stock	4,200,032	4,143,203
Parent Company [Member]
Preferred Stock, Shares Outstanding	867,846		867,846
Preferred Stock, Liquidation Preference Per Share	$ 50		$ 50
Common stock, shares outstanding	113,627,014		113,518,212
Proceeds from Stock Options Exercised	$ 432	$ 0
Employee Stock Option [Member]
Common stock shares, outstanding option	108,438	39,084

Partners' Capital of Mid-Amer50

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

Legal Proceedings (Details)

Legal Proceedings (Details) - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016
Loss Contingencies [Line Items]
Loss Contingency Accrual	$ 35.1	$ 42.1

Segment Information - Additiona

Segment Information - Additional Information (Detail) - 9 months ended Sep. 30, 2017 individual in Millions	Total	Property	States	Communities	individual
Segment Reporting Information [Line Items]
Number of owned or owned interests of apartment communities		303		302
Number of states in which apartment units are located | States			17
Period properties owned and stabilized	12 months
Occupancy Level for Stabilized Communities	90.00%
Period Properties Stabilized	90 days
Large Market Same Store [Member]
Segment Reporting Information [Line Items]
Apartment Community Population					1
Percentage of Total Public Multifamily REIT Units	1.00%
Period properties owned and stabilized	12 months
Secondary Market Same Store [Member]
Segment Reporting Information [Line Items]
Apartment Community Population					1
Percentage of Total Public Multifamily REIT Units	1.00%
Period properties owned and stabilized	12 months

Revenues and NOI for Reportable

Revenues and NOI for Reportable Segment (Detail) - Parent Company [Member] - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Segment Information
Total operating revenues	$ 384,550	$ 276,898	$ 1,146,249	$ 818,150
Net Operating Income	235,371	170,252	709,828	507,668
Depreciation and amortization	(117,928)	(76,959)	(374,285)	(227,829)
Acquisition expense	0	(1,033)	0	(2,167)
Property management expense	(10,281)	(7,908)	(32,007)	(25,221)
General and administrative expense	(8,361)	(6,661)	(30,735)	(20,257)
Merger related expenses	(128)	(3,901)	(3,977)	(3,901)
Business Combination, Integration Related Costs	(4,002)	0	(10,521)	0
Interest and other non-property (expense) income	4,303	64	7,632	159
Interest expense	(39,940)	(32,168)	(115,005)	(96,418)
Loss on debt extinguishment	828	0	3,168	3
Gain on sale of depreciable real estate assets excluded from discontinued operations	58,844	47,749	59,045	48,572
Net casualty loss after insurance and other settlement proceeds	564	(75)	233	738
Income tax expense	(641)	(454)	(1,910)	(1,200)
Gain on sale of non-depreciable real estate assets	(6)	0	42	2,170
Gain (loss) from real estate joint ventures	335	0	1,021	27
Net income attributable to noncontrolling interests	(4,249)	(4,627)	(7,600)	(9,508)
Preferred Stock Dividends, Income Statement Impact	(922)	0	(2,766)	0
Net Income (Loss) Available to Common Stockholders, Basic	113,787	84,279	202,163	172,836
Large Market Same Store
Segment Information
Total property revenues	169,105	165,046	503,076	487,725
Net Operating Income	104,574	101,595	313,419	302,230
Secondary Market Same Store
Segment Information
Total property revenues	87,895	85,822	261,272	254,685
Net Operating Income	53,836	53,124	162,617	159,263
Non-Same Store and Other
Segment Information
Total property revenues	127,550	26,030	381,901	75,740
Net Operating Income	$ 76,961	$ 15,533	$ 233,792	$ 46,175

Assets for Reportable Segment (

Assets for Reportable Segment (Detail) - Parent Company [Member] - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	$ 11,532,801	$ 11,604,491
Large Market Same Store
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	4,038,127	4,126,885
Secondary Market Same Store
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	1,731,050	1,768,183
Non-Same Store and Other
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	5,527,583	5,479,780
Corporate assets
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	$ 236,041	$ 229,643

Real Estate Acquisitions and 55

Real Estate Acquisitions and Dispositions - Additional Information (Details)	Sep. 30, 2017aapartmentunits	Mar. 31, 2017apartmentunits
Charlotte at MIdtown [Member]
Business Acquisitions and Dispositions [Line Items]
Number of Units in Real Estate Property | apartmentunits		279
Colonial Grand at Lakewood Ranch [Member]
Business Acquisitions and Dispositions [Line Items]
Area of Land | a	12
Paddock Club Lakeland [Member]
Business Acquisitions and Dispositions [Line Items]
Number of Units in Real Estate Property | apartmentunits	464
Area of Land | a	9
Northwood [Member]
Business Acquisitions and Dispositions [Line Items]
Number of Units in Real Estate Property | apartmentunits	270
Town Park Lot [Member]
Business Acquisitions and Dispositions [Line Items]
Area of Land | a	1
Paddock Club Montgomery [Member]
Business Acquisitions and Dispositions [Line Items]
Number of Units in Real Estate Property | apartmentunits	208
Post Alexander [Member]
Business Acquisitions and Dispositions [Line Items]
Area of Land | a	1