Basis of Presentation and Principles of Consolidation (Policies)	3 Months Ended
Mar. 31, 2019
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 the Company's 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, directly or indirectly, approximately 80% 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, 80% to 100% of all consolidated subsidiaries. In management's 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. The Company invests 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. The Company consolidates all VIEs for which it is the primary beneficiary and uses the equity method to account for investments that qualify as VIEs but for which it is not the primary beneficiary. In determining whether the Company is the primary beneficiary of a VIE, management considers both 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. The Company uses the equity method of accounting for its investments in entities for which the Company exercises significant influence, but does not have the ability to exercise control. The factors considered in determining whether the Company has the ability to exercise control include ownership of voting interests and participatory rights of investors (see "Investments in Unconsolidated Affiliates" below). Changes in Presentation In an effort to simplify the Company's presentation of cash flows from financing activities within the condensed consolidated statements of cash flows, the Company combined "Repurchase of common stock"; "Debt prepayment and extinguishment costs"; "Proceeds from issuances of common shares"; and "Exercise of stock options" into one line, "Net change in other financing activities" within the cash flows from financing activities section. No presentation changes were made to the cash flows from operating or investing activities sections of the condensed consolidated statements of cash flows. Prior year amounts have been changed to conform to the Company's current year presentation. These changes in presentation had no effect on the Company's ending cash, cash equivalents and restricted cash balances and did not impact the classification of cash flows between operating, investing and financing activities. Noncontrolling Interests As of March 31, 2019, the Company had two types of noncontrolling interests with respect to its consolidated subsidiaries, (1) noncontrolling interests related to the common unitholders of its Operating Partnership (see below) and (2) noncontrolling interest related to its consolidated real estate entities (see "Investment in Consolidated Real Estate Entities" below). The noncontrolling interests in the accompanying condensed consolidated financial statements relating to the limited partnership interests in the Operating Partnership are owned by the holders of the Class A OP Units. MAA is the sole general partner of the Operating Partnership and holds all of the outstanding Class B OP Units. Net income (after allocations to preferred ownership interests) is allocated to MAA and the noncontrolling interests based on their respective ownership percentages of the Operating Partnership. Issuance of additional Class A OP Units or Class B OP Units changes the ownership percentage of both the noncontrolling interests and MAA. The issuance of Class B OP Units generally occurs when MAA issues common stock and the issuance proceeds are contributed to the Operating Partnership in exchange for Class B OP Units equal to the number of shares of MAA's common stock issued. At each reporting period, the allocation between total MAA shareholders’ equity and noncontrolling interests is adjusted to account for the change in the respective percentage ownership of the underlying equity of the Operating Partnership. MAA’s Board of Directors established economic rights in respect to each Class A OP Unit that were equivalent to the economic rights in respect to each share of MAA common stock. See Note 9 for additional details. Investments in Unconsolidated Affiliates Through its investment in a limited liability company, or the Apartment LLC, the Company together with an institutional investor indirectly owns one apartment community, Post Massachusetts Avenue, located in Washington, D.C. The Company owned a 35.0% equity interest in the unconsolidated real estate joint venture as of March 31, 2019 and provides property and asset management services to the Apartment LLC for which it earns fees. The joint venture was determined to be a VIE, but the Company is not designated as a primary beneficiary. As a result, the Company accounts for its investment in the Apartment LLC using the equity method of accounting as the Company is able to exert significant influence over the joint venture but does not have a controlling interest. As of March 31, 2019, the Company's investment in the Apartment LLC totaled $44.1 million. In September 2017, a subsidiary of the Operating Partnership invested in a limited partnership, Real Estate Technology Ventures, L.P. As of March 31, 2019, the Operating Partnership indirectly owned 20.7% of the limited partnership. The limited partnership was determined to be a VIE, but the Company is not designated as a primary beneficiary. As a result, the Company accounts for its investment in the limited partnership using the equity method of accounting as the investment is considered more than minor. As of March 31, 2019, the Company's investment in the limited partnership totaled $3.7 million and is included in "Other assets" in the accompanying Condensed Consolidated Balance Sheet. As of March 31, 2019, the Company was committed to make additional capital contributions totaling $13.6 million if and when called by the general partner of the limited partnership and until September 2022. Investments in Consolidated Real Estate Entities The Company owns a 92.5% equity interest in a consolidated real estate entity that developed, constructed and operates a 359-unit apartment community in Denver, Colorado. The owner of the remaining 7.5% equity interest, a private real estate company, was generally responsible for the development and construction of the community, which was completed during the year ended December 31, 2018. The Company will continue to operate and manage the community. The entity was determined to be a VIE with the Company designated as the primary beneficiary. As a result, the accounts of the entity are consolidated by the Company. As of March 31, 2019, the consolidated assets and liabilities included buildings and improvements and other, net of accumulated depreciation of $69.8 million; land of $14.9 million; and accrued expenses and other liabilities of $1.0 million. During the first quarter of 2019, the Company acquired an 80.0% equity interest in a consolidated real estate entity that will develop, construct and operate an apartment community in Phoenix, Arizona. The joint venture acquired the land site and initiated development of the apartment community in the first quarter of 2019. The owner of the remaining 20.0% equity interest, a private real estate company, is responsible for the development and construction of the community, and the Company will operate and manage the community upon its completion. The entity was determined to be a VIE with the Company designated as the primary beneficiary. As a result, the accounts of the entity are consolidated by the Company. As of March 31, 2019, the consolidated assets and liabilities included development and capital improvements in process of $4.7 million; land of $9.4 million; and accrued expenses and other liabilities of $0.7 million. Fair Value Measurements The Company applies the guidance in Accounting Standards Codification, or ASC, Topic 820, Fair Value Measurements and Disclosures, to the valuation of real estate assets recorded at fair value, if any; to its impairment valuation analysis of real estate assets; to its disclosure of the fair value of financial instruments, principally indebtedness; and to its derivative financial instruments. Fair value disclosures required under ASC Topic 820 are summarized in Note 7 utilizing the following hierarchy: Level 1 - Quoted prices in active markets for identical assets or liabilities that are accessible at the measurement date. Level 2 - Inputs other than quoted prices that are observable for the asset or liability, either directly or indirectly. Level 3 - Unobservable inputs for the assets or liability. Leases In 2016, the Financial Accounting Standard Board, or FASB, issued Accounting Standard Update, or ASU, 2016-02, Leases (Topic 842), which established new principles, presentation and disclosure requirements for lease accounting for both the lessee and lessor. On January 1, 2019, management adopted ASU 2016-02 using the modified retrospective transition approach with an effective date as of the adoption date and elected certain practical expedients allowed by the new standard. Under the new standard, lessors are required to account for leases in a similar manner as previous lease accounting guidance but aligned with the newly adopted revenue recognition standard. Lessees are required to record most leases on the balance sheet and recognize lease expense in the income statement in a manner similar to previous practice. The new standard requires a lessee to recognize a lease liability for the obligation to make lease payments and a right-of-use asset for the right to use the underlying asset for all leases with terms of more than twelve months. Expenses related to leases determined to be operating leases are recognized on a straight-line basis, while expenses related to leases determined to be financing leases are recognized based on an effective interest method in which interest and amortization are presented separately in the income statement. Comparative periods presented in this Quarterly Report on Form 10-Q continue to apply guidance in ASC Topic 840, Leases, and have not been recast as the Company adopted the new standard using the modified retrospective transition approach effective as of January 1, 2019. The adoption of the new lease standard has not resulted in a significant change in the accounting for the Company’s rental revenues as the Company's residential, retail and commercial leases, where it is the lessor, will continue to be accounted for as operating leases. Management has elected available practical expedients that provide lessors an option not to separate lease and non-lease components when certain criteria are met, and instead, allow for those components to be accounted for as a single lease component. Thus, beginning with the effective date of the adoption of the new standard, January 1, 2019, rental revenues and non-lease reimbursable property revenues meet the criteria to be aggregated into a single lease component and are reported in the line item, "Rental revenues", as presented in the disaggregation of the Company's revenues in Note 11. The Company is the lessee under certain ground, office, equipment and other operating leases. Based on its election of the package of practical expedients provided in ASU 2016-02, the Company did not reassess the classification of existing leases with its adoption of ASC Topic 842. The Company’s existing leases as of January 1, 2019 will continue to be accounted for as operating leases; however, if contracts are modified subsequent to the adoption of ASC Topic 842, the Company will be required to reassess the contracts using guidance provided under ASC Topic 842. The Company recognized total right-of-use assets of $54.3 million within "Other assets" and related lease obligations of $33.6 million within "Accrued expenses and other liabilities" on its Condensed Consolidated Balance Sheets for leases in effect as of January 1, 2019. As most leases do not provide a readily determinable implicit rate to discount future minimum lease payments to present value, management estimated the Company's incremental borrowing rate based on information available as of the date of adoption and based on the remaining lease terms as of the date of initial application. Operating leases recognized upon adoption have a weighted-average remaining lease term of approximately 33 years and a weighted-average discount rate of approximately 4.4%. Lease expense for the three months ended March 31, 2019, recognized under ASC Topic 842, continued to be immaterial for the Company and was recognized in a similar manner as compared to the three months ended March 31, 2018. Cash paid for amounts included in the measurement of operating lease liabilities during the three months ended March 31, 2019 was also immaterial. Revenue Recognition The Company primarily leases multifamily residential apartments under operating leases generally due on a monthly basis with terms of approximately one year or less, which are recorded as operating leases. Rental revenues are recognized in accordance with ASC Topic 842 using a method that represents a straight-line basis over the term of the lease. In addition, in circumstances where a lease incentive is provided to tenants, the incentive is recognized as a reduction of rental revenues on a straight-line basis over the reasonably assured lease term. Rental revenues represent approximately 93% of the Company's total revenues and include gross market rent less adjustments for concessions, vacancy loss and bad debt. Approximately 6% of the Company's total revenues represents reimbursable property revenues from its tenants for utility reimbursements, which are generally recognized and due on a monthly basis as tenants obtain control of the service over the term of the lease. The remaining 1% of the Company's total revenues represents other non-lease revenues primarily driven by nonrefundable fees and commissions. With the adoption of ASC Topic 842, rental revenues and non-lease reimbursable property revenues meet the criteria to be aggregated into a single lease component and to be reported in a single line, while non-lease reimbursable property revenues recognized prior to January 1, 2019 will continue to be reported as non-lease revenues and recognized in accordance with ASC Topic 606, Revenue Recognition. The guidance requires that revenue recognized outside of the scope of ASC Topic 842 is recognized when a customer obtains control of promised goods or services in an amount that reflects the consideration the entity expects to receive in exchange for those goods or services.

Basis of Presentation and Principles of Consolidation

The accompanying condensed consolidated financial statements have been prepared by the Company's 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, directly or indirectly, approximately 80% 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, 80% to 100% of all consolidated subsidiaries. In management's 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.

The Company invests 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. The Company consolidates all VIEs for which it is the primary beneficiary and uses the equity method to account for investments that qualify as VIEs but for which it is not the primary beneficiary. In determining whether the Company is the primary beneficiary of a VIE, management considers both 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. The Company uses the equity method of accounting for its investments in entities for which the Company exercises significant influence, but does not have the ability to exercise control. The factors considered in determining whether the Company has the ability to exercise control include ownership of voting interests and participatory rights of investors (see "Investments in Unconsolidated Affiliates" below).

Changes in Presentation

In an effort to simplify the Company's presentation of cash flows from financing activities within the condensed consolidated statements of cash flows, the Company combined "Repurchase of common stock"; "Debt prepayment and extinguishment costs"; "Proceeds from issuances of common shares"; and "Exercise of stock options" into one line, "Net change in other financing activities" within the cash flows from financing activities section. No presentation changes were made to the cash flows from operating or investing activities sections of the condensed consolidated statements of cash flows. Prior year amounts have been changed to conform to the Company's current year presentation. These changes in presentation had no effect on the Company's ending cash, cash equivalents and restricted cash balances and did not impact the classification of cash flows between operating, investing and financing activities.

Noncontrolling Interests

As of March 31, 2019, the Company had two types of noncontrolling interests with respect to its consolidated subsidiaries, (1) noncontrolling interests related to the common unitholders of its Operating Partnership (see below) and (2) noncontrolling interest related to its consolidated real estate entities (see "Investment in Consolidated Real Estate Entities" below). The noncontrolling interests in the accompanying condensed consolidated financial statements relating to the limited partnership interests in the Operating Partnership are owned by the holders of the Class A OP Units. MAA is the sole general partner of the Operating Partnership and holds all of the outstanding Class B OP Units. Net income (after allocations to preferred ownership interests) is allocated to MAA and the noncontrolling interests based on their respective ownership percentages of the Operating Partnership. Issuance of additional Class A OP Units or Class B OP Units changes the ownership percentage of both the noncontrolling interests and MAA. The issuance of Class B OP Units generally occurs when MAA issues common stock and the issuance proceeds are contributed to the Operating Partnership in exchange for Class B OP Units equal to the number of shares of MAA's common stock issued. At each reporting period, the allocation between total MAA shareholders’ equity and noncontrolling interests is adjusted to account for the change in the respective percentage ownership of the underlying equity of the Operating Partnership. MAA’s Board of Directors established economic rights in respect to each Class A OP Unit that were equivalent to the economic rights in respect to each share of MAA common stock. See Note 9 for additional details.

Investments in Unconsolidated Affiliates

Through its investment in a limited liability company, or the Apartment LLC, the Company together with an institutional investor indirectly owns one apartment community, Post Massachusetts Avenue, located in Washington, D.C. The Company owned a 35.0% equity interest in the unconsolidated real estate joint venture as of March 31, 2019 and provides property and asset management services to the Apartment LLC for which it earns fees. The joint venture was determined to be a VIE, but the Company is not designated as a primary beneficiary. As a result, the Company accounts for its investment in the Apartment LLC using the equity method of accounting as the Company is able to exert significant influence over the joint venture but does not have a controlling interest. As of March 31, 2019, the Company's investment in the Apartment LLC totaled $44.1 million.

In September 2017, a subsidiary of the Operating Partnership invested in a limited partnership, Real Estate Technology Ventures, L.P. As of March 31, 2019, the Operating Partnership indirectly owned 20.7% of the limited partnership. The limited partnership was determined to be a VIE, but the Company is not designated as a primary beneficiary. As a result, the Company accounts for its investment in the limited partnership using the equity method of accounting as the investment is considered more than minor. As of March 31, 2019, the Company's investment in the limited partnership totaled $3.7 million and is included in "Other assets" in the accompanying Condensed Consolidated Balance Sheet. As of March 31, 2019, the Company was committed to make additional capital contributions totaling $13.6 million if and when called by the general partner of the limited partnership and until September 2022.

Investments in Consolidated Real Estate Entities

The Company owns a 92.5% equity interest in a consolidated real estate entity that developed, constructed and operates a 359-unit apartment community in Denver, Colorado. The owner of the remaining 7.5% equity interest, a private real estate company, was generally responsible for the development and construction of the community, which was completed during the year ended December 31, 2018. The Company will continue to operate and manage the community. The entity was determined to be a VIE with the Company designated as the primary beneficiary. As a result, the accounts of the entity are consolidated by the Company. As of March 31, 2019, the consolidated assets and liabilities included buildings and improvements and other, net of accumulated depreciation of $69.8 million; land of $14.9 million; and accrued expenses and other liabilities of $1.0 million.

During the first quarter of 2019, the Company acquired an 80.0% equity interest in a consolidated real estate entity that will develop, construct and operate an apartment community in Phoenix, Arizona. The joint venture acquired the land site and initiated development of the apartment community in the first quarter of 2019. The owner of the remaining 20.0% equity interest, a private real estate company, is responsible for the development and construction of the community, and the Company will operate and manage the community upon its completion. The entity was determined to be a VIE with the Company designated as the primary beneficiary. As a result, the accounts of the entity are consolidated by the Company. As of March 31, 2019, the consolidated assets and liabilities included development and capital improvements in process of $4.7 million; land of $9.4 million; and accrued expenses and other liabilities of $0.7 million.

Fair Value Measurements

The Company applies the guidance in Accounting Standards Codification, or ASC, Topic 820, Fair Value Measurements and Disclosures, to the valuation of real estate assets recorded at fair value, if any; to its impairment valuation analysis of real estate assets; to its disclosure of the fair value of financial instruments, principally indebtedness; and to its derivative financial instruments. Fair value disclosures required under ASC Topic 820 are summarized in Note 7 utilizing the following hierarchy:

Level 1 - Quoted prices in active markets for identical assets or liabilities that are accessible at the measurement date.

Level 2 - Inputs other than quoted prices that are observable for the asset or liability, either directly or indirectly.

Level 3 - Unobservable inputs for the assets or liability.

Leases

In 2016, the Financial Accounting Standard Board, or FASB, issued Accounting Standard Update, or ASU, 2016-02, Leases (Topic 842), which established new principles, presentation and disclosure requirements for lease accounting for both the lessee and lessor. On January 1, 2019, management adopted ASU 2016-02 using the modified retrospective transition approach with an effective date as of the adoption date and elected certain practical expedients allowed by the new standard. Under the new standard, lessors are required to account for leases in a similar manner as previous lease accounting guidance but aligned with the newly adopted revenue recognition standard. Lessees are required to record most leases on the balance sheet and recognize lease expense in the income statement in a manner similar to previous practice. The new standard requires a lessee to recognize a lease liability for the obligation to make lease payments and a right-of-use asset for the right to use the underlying asset for all leases with terms of more than twelve months. Expenses related to leases determined to be operating leases are recognized on a straight-line basis, while expenses related to leases determined to be financing leases are recognized based on an effective interest method in which interest and amortization are presented separately in the income statement.

Comparative periods presented in this Quarterly Report on Form 10-Q continue to apply guidance in ASC Topic 840, Leases, and have not been recast as the Company adopted the new standard using the modified retrospective transition approach effective as of January 1, 2019. The adoption of the new lease standard has not resulted in a significant change in the accounting for the Company’s rental revenues as the Company's residential, retail and commercial leases, where it is the lessor, will continue to be accounted for as operating leases. Management has elected available practical expedients that provide lessors an option not to separate lease and non-lease components when certain criteria are met, and instead, allow for those components to be accounted for as a single lease component. Thus, beginning with the effective date of the adoption of the new standard, January 1, 2019, rental revenues and non-lease reimbursable property revenues meet the criteria to be aggregated into a single lease component and are reported in the line item, "Rental revenues", as presented in the disaggregation of the Company's revenues in Note 11.

The Company is the lessee under certain ground, office, equipment and other operating leases. Based on its election of the package of practical expedients provided in ASU 2016-02, the Company did not reassess the classification of existing leases with its adoption of ASC Topic 842. The Company’s existing leases as of January 1, 2019 will continue to be accounted for as operating leases; however, if contracts are modified subsequent to the adoption of ASC Topic 842, the Company will be required to reassess the contracts using guidance provided under ASC Topic 842. The Company recognized total right-of-use assets of $54.3 million within "Other assets" and related lease obligations of $33.6 million within "Accrued expenses and other liabilities" on its Condensed Consolidated Balance Sheets for leases in effect as of January 1, 2019. As most leases do not provide a readily determinable implicit rate to discount future minimum lease payments to present value, management estimated the Company's incremental borrowing rate based on information available as of the date of adoption and based on the remaining lease terms as of the date of initial application. Operating leases recognized upon adoption have a weighted-average remaining lease term of approximately 33 years and a weighted-average discount rate of approximately 4.4%. Lease expense for the three months ended March 31, 2019, recognized under ASC Topic 842, continued to be immaterial for the Company and was recognized in a similar manner as compared to the three months ended March 31, 2018. Cash paid for amounts included in the measurement of operating lease liabilities during the three months ended March 31, 2019 was also immaterial.

Revenue Recognition

The Company primarily leases multifamily residential apartments under operating leases generally due on a monthly basis with terms of approximately one year or less, which are recorded as operating leases. Rental revenues are recognized in accordance with ASC Topic 842 using a method that represents a straight-line basis over the term of the lease. In addition, in circumstances where a lease incentive is provided to tenants, the incentive is recognized as a reduction of rental revenues on a straight-line basis over the reasonably assured lease term. Rental revenues represent approximately 93% of the Company's total revenues and include gross market rent less adjustments for concessions, vacancy loss and bad debt. Approximately 6% of the Company's total revenues represents reimbursable property revenues from its tenants for utility reimbursements, which are generally recognized and due on a monthly basis as tenants obtain control of the service over the term of the lease. The remaining 1% of the Company's total revenues represents other non-lease revenues primarily driven by nonrefundable fees and commissions.

With the adoption of ASC Topic 842, rental revenues and non-lease reimbursable property revenues meet the criteria to be aggregated into a single lease component and to be reported in a single line, while non-lease reimbursable property revenues recognized prior to January 1, 2019 will continue to be reported as non-lease revenues and recognized in accordance with ASC Topic 606, Revenue Recognition. The guidance requires that revenue recognized outside of the scope of ASC Topic 842 is recognized when a customer obtains control of promised goods or services in an amount that reflects the consideration the entity expects to receive in exchange for those goods or services.