Basis of Presentation and Principles of Consolidation (Policies)	6 Months Ended
Jun. 30, 2018
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 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 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 "Investment in Unconsolidated Affiliates" below). Changes in Presentation Please refer to the Company's Annual Report on Form 10-K for the year ended December 31, 2017 that the Company filed with the SEC on February 23, 2018 for discussions of the changes in presentation in the Condensed Consolidated Balance Sheets, Condensed Consolidated Statements of Operations and Condensed Consolidated Statements of Cash Flows, which are applicable for this Quarterly Report on Form 10-Q. Noncontrolling Interests At June 30, 2018, the Company had two types of noncontrolling interests, (1) noncontrolling interests related to the common unitholders of its Operating Partnership (see Note 9) and (2) noncontrolling interest related to its consolidated real estate entity (see "Investment in Consolidated Real Estate Entity" below). Investment in Unconsolidated Affiliates The Company, together with other institutional investors in a limited liability company, or the Apartment LLC, indirectly owns one apartment community, Post Massachusetts Avenue, located in Washington, D.C. The Company owns a 35.0% equity interest in the unconsolidated real estate joint venture as of June 30, 2018 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. At June 30, 2018, the Company's investment in the Apartment LLC totaled $44.8 million. During September 2017, a subsidiary of the Operating Partnership entered into a limited partnership together with a general partner and other limited partners to form Real Estate Technology Ventures, L.P. The Operating Partnership indirectly owns 25.2% 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. At June 30, 2018, the Company's investment in the limited partnership totaled $1.9 million. As of June 30, 2018, the Company was committed to make additional capital contributions totaling $12.8 million if and when called by the general partner of the limited partnership prior to September 2022. Investment in Consolidated Real Estate Entity At June 30, 2018, the Company owned a 92.5% equity interest in a consolidated real estate joint venture to develop, construct and operate a 359-unit apartment community in Denver, Colorado, along with a private real estate company. The venture partner was generally responsible for the development and construction of the community, and the Company will continue to manage the community as construction on the development was completed during the six months ended June 30, 2018. 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. At June 30, 2018, the consolidated assets, liabilities and equity included buildings and improvements and other, net of accumulated depreciation of $70.7 million; land of $14.9 million; and accrued expenses and other liabilities of $1.3 million. Assets Held for Sale During the second quarter of 2018, the criteria for classifying one land parcel located in the Atlanta, Georgia market as held for sale were met, and as a result, the land parcel was presented as held for sale in the Condensed Consolidated Balance Sheet as of June 30, 2018. See Note 13 for details on the July 2018 disposition of this land parcel. The Randal Park land parcel that comprised the asset held for sale balance as of December 31, 2017, was sold during the first quarter of 2018 as detailed in Note 12. 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. Revenue from Contracts with Customers The Company primarily leases multifamily residential apartments under operating leases generally with terms of one year or less, which are recorded as operating leases. Rental lease revenues are recognized in accordance with ASC Topic 840, Leases, using a method that represents a straight-line basis over the term of the lease. Rental income represents approximately 93% of the Company's total revenues and includes gross market rent less adjustments for concessions, vacancy loss and bad debt. Other non-lease revenues represent the remaining 7% of the Company's total revenues and are primarily driven by utility reimbursement revenue from its tenants. The Company's primary sources of reimbursement revenue are from water and cable utility services, which produced $19.3 million and $14.9 million, respectively, of revenues during the six months ended June 30, 2018, and $18.8 million and $15.3 million of revenues, respectively, during the six months ended June 30, 2017. Other non-lease revenues are recognized in accordance with ASC Topic 606, Revenue Recognition, as a result of the Company's January 1, 2018 adoption of Accounting Standards Update, or ASU, 2014-09, Revenue from Contracts with Customers, using the modified retrospective approach. The guidance requires that revenue (outside of the scope of lease revenue accounting rules) 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. While ASU 2014-09 requires additional disclosure regarding the nature and timing of the Company's non-lease revenue transactions, which is provided here in Note 1 as well as Note 11, the adoption of the ASU did not have a material impact on the Company's consolidated financial statements or the Company's internal accounting policies and did not result in an opening adjustment to retained earnings. In addition, the Company elected the available practical expedients to the ASU’s requirement for disclosure on remaining performance obligations, which allow an entity to avoid disclosing the amount of the remaining performance obligations for contracts with an original expected duration of less than one year or those that meet the practical expedient in ASC 606-10-55-18 that permits the entity to recognize revenue as invoiced. See Note 11 for the disaggregation of the Company's revenues in accordance with ASU 2014-09. Impact of Recently Adopted Accounting Standards on Condensed Consolidated Statements of Cash Flows Effective January 1, 2018, the Company adopted ASU 2016-15, Classification of Certain Cash Receipts and Cash Payments (a Consensus of the FASB Emerging Issues Task Force), which clarifies how certain types of cash receipts and cash payments are to be presented and classified on the statement of cash flows. Management determined that three of the eight transactions in the ASU are relevant to the Company and its cash flows and include debt prepayment and extinguishment costs, proceeds from the settlement of insurance claims and distributions received from equity method investees. Upon adoption of ASU 2016-15, the Company recognized a $1.6 million increase to net cash provided by operating activities and a $1.6 million decrease to net cash used in financing activities for the six months ended June 30, 2017. The Company adopted ASU 2016-18, Statement of Cash Flows (Topic 230): Restricted Cash (A Consensus of the FASB Emerging Issues Task Force), effective January 1, 2018. The ASU required restricted cash to be presented within cash and cash equivalents when reconciling the beginning and ending amounts in the statement of cash flow with retrospective adjustments to all periods presented. The Company previously reported the change in restricted cash within the operating and investing activities in the consolidated statement of cash flows. Upon adoption, cash, cash equivalents and restricted cash reported in the Condensed Consolidated Statements of Cash Flows for the six months ended June 30, 2017 increased by approximately $27.9 million to reflect the restricted cash balances. Additionally, net cash provided by operating activities decreased by $2.1 million for the six months ended June 30, 2017, while net cash used in investing activities decreased by $58.3 million for the six months ended June 30, 2017. Recently Issued Accounting Pronouncements The Company believes the following recent accounting pronouncement is relevant to the readers of the Company's financial statements and could have a material effect on the Company's consolidated financial statements. In 2016, the Financial Accounting Standard Board, or FASB, issued a new lease accounting standard, ASU 2016-02, Leases (Topic 842), which amends existing accounting standards and establishes new principles, presentation and disclosure requirements for lease accounting for both the lessee and lessor. Under the new standard, lessors will use an approach that is substantially equivalent to existing guidance but aligned with the newly adopted revenue recognition standard, while lessees will be required to record most leases on the balance sheet and recognize lease expense in the income statement in a manner similar to current 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 will be recognized on a straight-line basis, while those determined to be financing leases will be recognized following a front-loaded expense profile in which interest and amortization are presented separately in the income statement. The standard must be adopted using a modified retrospective transition approach. Entities have the option to apply the transition approach in the earliest period presented or in the period of adoption. If an entity elects to apply the transition approach in the period of adoption, prior period financial statements and disclosures would be presented in accordance with existing leases guidance. Management is currently evaluating the impact the standard will have on the consolidated financial statements and related disclosures upon adoption on January 1, 2019.

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 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 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 "Investment in Unconsolidated Affiliates" below).

Changes in Presentation

Please refer to the Company's Annual Report on Form 10-K for the year ended December 31, 2017 that the Company filed with the SEC on February 23, 2018 for discussions of the changes in presentation in the Condensed Consolidated Balance Sheets, Condensed Consolidated Statements of Operations and Condensed Consolidated Statements of Cash Flows, which are applicable for this Quarterly Report on Form 10-Q.

Noncontrolling Interests

At June 30, 2018, the Company had two types of noncontrolling interests, (1) noncontrolling interests related to the common unitholders of its Operating Partnership (see Note 9) and (2) noncontrolling interest related to its consolidated real estate entity (see "Investment in Consolidated Real Estate Entity" below).

Investment in Unconsolidated Affiliates

The Company, together with other institutional investors in a limited liability company, or the Apartment LLC, indirectly owns one apartment community, Post Massachusetts Avenue, located in Washington, D.C. The Company owns a 35.0% equity interest in the unconsolidated real estate joint venture as of June 30, 2018 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. At June 30, 2018, the Company's investment in the Apartment LLC totaled $44.8 million.

During September 2017, a subsidiary of the Operating Partnership entered into a limited partnership together with a general partner and other limited partners to form Real Estate Technology Ventures, L.P. The Operating Partnership indirectly owns 25.2% 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. At June 30, 2018, the Company's investment in the limited partnership totaled $1.9 million. As of June 30, 2018, the Company was committed to make additional capital contributions totaling $12.8 million if and when called by the general partner of the limited partnership prior to September 2022.

Investment in Consolidated Real Estate Entity

At June 30, 2018, the Company owned a 92.5% equity interest in a consolidated real estate joint venture to develop, construct and operate a 359-unit apartment community in Denver, Colorado, along with a private real estate company. The venture partner was generally responsible for the development and construction of the community, and the Company will continue to manage the community as construction on the development was completed during the six months ended June 30, 2018. 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. At June 30, 2018, the consolidated assets, liabilities and equity included buildings and improvements and other, net of accumulated depreciation of $70.7 million; land of $14.9 million; and accrued expenses and other liabilities of $1.3 million.

Assets Held for Sale

During the second quarter of 2018, the criteria for classifying one land parcel located in the Atlanta, Georgia market as held for sale were met, and as a result, the land parcel was presented as held for sale in the Condensed Consolidated Balance Sheet as of June 30, 2018. See Note 13 for details on the July 2018 disposition of this land parcel. The Randal Park land parcel that comprised the asset held for sale balance as of December 31, 2017, was sold during the first quarter of 2018 as detailed in Note 12.

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.

Revenue from Contracts with Customers

The Company primarily leases multifamily residential apartments under operating leases generally with terms of one year or less, which are recorded as operating leases. Rental lease revenues are recognized in accordance with ASC Topic 840, Leases, using a method that represents a straight-line basis over the term of the lease. Rental income represents approximately 93% of the Company's total revenues and includes gross market rent less adjustments for concessions, vacancy loss and bad debt.

Other non-lease revenues represent the remaining 7% of the Company's total revenues and are primarily driven by utility reimbursement revenue from its tenants. The Company's primary sources of reimbursement revenue are from water and cable utility services, which produced $19.3 million and $14.9 million, respectively, of revenues during the six months ended June 30, 2018, and $18.8 million and $15.3 million of revenues, respectively, during the six months ended June 30, 2017.

Other non-lease revenues are recognized in accordance with ASC Topic 606, Revenue Recognition, as a result of the Company's January 1, 2018 adoption of Accounting Standards Update, or ASU, 2014-09, Revenue from Contracts with Customers, using the modified retrospective approach. The guidance requires that revenue (outside of the scope of lease revenue accounting rules) 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. While ASU 2014-09 requires additional disclosure regarding the nature and timing of the Company's non-lease revenue transactions, which is provided here in Note 1 as well as Note 11, the adoption of the ASU did not have a material impact on the Company's consolidated financial statements or the Company's internal accounting policies and did not result in an opening adjustment to retained earnings. In addition, the Company elected the available practical expedients to the ASU’s requirement for disclosure on remaining performance obligations, which allow an entity to avoid disclosing the amount of the remaining performance obligations for contracts with an original expected duration of less than one year or those that meet the practical expedient in ASC 606-10-55-18 that permits the entity to recognize revenue as invoiced. See Note 11 for the disaggregation of the Company's revenues in accordance with ASU 2014-09.

Impact of Recently Adopted Accounting Standards on Condensed Consolidated Statements of Cash Flows

Effective January 1, 2018, the Company adopted ASU 2016-15, Classification of Certain Cash Receipts and Cash Payments (a

Consensus of the FASB Emerging Issues Task Force), which clarifies how certain types of cash receipts and cash payments are to be presented and classified on the statement of cash flows. Management determined that three of the eight transactions in the ASU are relevant to the Company and its cash flows and include debt prepayment and extinguishment costs, proceeds from the settlement of insurance claims and distributions received from equity method investees. Upon adoption of ASU 2016-15, the Company recognized a $1.6 million increase to net cash provided by operating activities and a $1.6 million decrease to net cash used in financing activities for the six months ended June 30, 2017.

The Company adopted ASU 2016-18, Statement of Cash Flows (Topic 230): Restricted Cash (A Consensus of the FASB Emerging Issues Task Force), effective January 1, 2018. The ASU required restricted cash to be presented within cash and cash equivalents when reconciling the beginning and ending amounts in the statement of cash flow with retrospective adjustments to all periods presented. The Company previously reported the change in restricted cash within the operating and investing activities in the consolidated statement of cash flows. Upon adoption, cash, cash equivalents and restricted cash reported in the Condensed Consolidated Statements of Cash Flows for the six months ended June 30, 2017 increased by approximately $27.9 million to reflect the restricted cash balances. Additionally, net cash provided by operating activities decreased by $2.1 million for the six months ended June 30, 2017, while net cash used in investing activities decreased by $58.3 million for the six months ended June 30, 2017.

Recently Issued Accounting Pronouncements

The Company believes the following recent accounting pronouncement is relevant to the readers of the Company's financial statements and could have a material effect on the Company's consolidated financial statements.

In 2016, the Financial Accounting Standard Board, or FASB, issued a new lease accounting standard, ASU 2016-02, Leases (Topic 842), which amends existing accounting standards and establishes new principles, presentation and disclosure requirements for lease accounting for both the lessee and lessor. Under the new standard, lessors will use an approach that is substantially equivalent to existing guidance but aligned with the newly adopted revenue recognition standard, while lessees will be required to record most leases on the balance sheet and recognize lease expense in the income statement in a manner similar to current 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 will be recognized on a straight-line basis, while those determined to be financing leases will be recognized following a front-loaded expense profile in which interest and amortization are presented separately in the income statement.

The standard must be adopted using a modified retrospective transition approach. Entities have the option to apply the transition approach in the earliest period presented or in the period of adoption. If an entity elects to apply the transition approach in the period of adoption, prior period financial statements and disclosures would be presented in accordance with existing leases guidance. Management is currently evaluating the impact the standard will have on the consolidated financial statements and related disclosures upon adoption on January 1, 2019.