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Earnings Per OP Unit of MAALP (Tables) | 9 Months Ended
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Sep. 30, 2018
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, 2018 and 2017 is presented below (dollars and units in thousands, except per unit amounts):
| Three months ended September 30, |  | Nine months ended September 30,
| 2018 |  | 2017 |  | 2018 |  | 2017
Calculation of Earnings per Common Unit - basic |  |  |  |  |  |  |  |  |
Net income | $ | 54,704 |  |  | $ | 118,958 |  |  | $ | 167,505 |  |  | $ | 212,529 |
Unvested restricted stock (allocation of earnings) | (69 | ) |  | (181 | ) |  | (211 | ) |  | (337 | )
Preferred unit distributions | (922 | ) |  | (922 | ) |  | (2,766 | ) |  | (2,766 | )
Net income available for common unitholders, adjusted | $ | 53,713 |  |  | $ | 117,855 |  |  | $ | 164,528 |  |  | $ | 209,426 |
Weighted average common units - basic | 117,796 |  |  | 117,643 |  |  | 117,768 |  |  | 117,607 |
Earnings per common unit - basic | $ | 0.46 |  |  | $ | 1.00 |  |  | $ | 1.40 |  |  | $ | 1.78 |
Calculation of Earnings per Common Unit - diluted |  |  |  |  |  |  |  |  |
Net income | $ | 54,704 |  |  | $ | 118,958 |  |  | $ | 167,505 |  |  | $ | 212,529 |
Preferred unit distributions | (922 | ) |  | (922 | ) |  | (2,766 | ) |  | (2,766 | )
Net income available for common unitholders, adjusted | $ | 53,782 |  |  | $ | 118,036 |  |  | $ | 164,739 |  |  | $ | 209,763 |
Weighted average common shares - basic | 117,796 |  |  | 117,643 |  |  | 117,768 |  |  | 117,607 |
Effect of dilutive securities | 239 |  |  | 219 |  |  | 201 |  |  | 270 |
Weighted average common units - diluted | 118,035 |  |  | 117,862 |  |  | 117,969 |  |  | 117,877 |
Earnings per common unit - diluted | $ | 0.46 |  |  | $ | 1.00 |  |  | $ | 1.40 |  |  | $ | 1.78 |

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- Definition Earnings Per OP Unit of MAALP [Abstract] + References No definition available. + Details
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- Definition Schedule of Earnings Per Unit, Basic and Diluted [Table Text Block] + References No definition available. + Details
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Namespace Prefix: | maa_
Data Type: | nonnum:textBlockItemType
Balance Type: | na
Period Type: | duration