Earnings per Share/Unit	3 Months Ended
Mar. 31, 2019
Earnings Per Share [Abstract]
Earnings per Share/Unit	Earnings and Dividends per Share and Unit Aimco and the Aimco Operating Partnership calculate basic earnings per common share and basic earnings per common unit based on the weighted average number of shares of Common Stock and common partnership units and participating securities outstanding, and calculate diluted earnings per share and diluted earnings per unit taking into consideration dilutive common stock and common partnership unit equivalents and dilutive convertible securities outstanding during the period. Our common stock and common partnership unit equivalents include options to purchase shares of Common Stock, which, if exercised, would result in Aimco’s issuance of additional shares and the Aimco Operating Partnership’s issuance to Aimco of additional common partnership units equal to the number of shares purchased under the options. These equivalents also include unvested total stockholder return, or TSR, restricted stock awards that do not meet the definition of participating securities, which would result in an increase in the number of shares of Common Stock and common partnership units outstanding equal to the number of shares that vest. The dilutive effect of these securities was 0.2 million and 0.1 million shares and 0.3 million and 0.1 million units for the three months ended March 31, 2019 and 2018, respectively. Securities with dilutive effect are included in the denominator for calculating diluted earnings per share and per unit during these periods. There were no shares and 0.2 million potential shares, and 0.4 million and 0.2 million potential units not dilutive and excluded from the denominator for calculating diluted earnings per share and per unit, respectively, for both the three months ended March 31, 2019 and 2018. Our time-based restricted stock awards receive dividends similar to shares of Common Stock and common partnership units prior to vesting, and our TSR long-term incentive partnership units receive a percentage of the distributions paid to common partnership units prior to vesting. These dividends and distributions are not forfeited if the awards fail to vest. Therefore, the unvested shares and units related to these awards are participating securities. The effect of participating securities is included in basic and diluted earnings per share and unit computations using the two-class method of allocating distributed and undistributed earnings when the two-class method is more dilutive than the treasury method. There were 0.2 million and 0.3 million unvested restricted participating shares and 0.2 million and 0.3 million unvested restricted participating units, for the three months ended March 31, 2019 and 2018, respectively. The Aimco Operating Partnership has various classes of preferred OP Units, which may be redeemed at the holders’ option. The Aimco Operating Partnership may redeem these units for cash, or at its option, shares of Common Stock. As of March 31, 2019, these preferred OP Units were potentially redeemable for approximately 2.0 million shares of Common Stock (based on the period end market price), or cash. The Aimco Operating Partnership has a redemption policy that requires cash settlement of redemption requests for the preferred OP Units, subject to limited exceptions. Accordingly, we have excluded these securities from earnings per share and unit computations and we expect to exclude them in future periods. During the three months ended March 31, 2019 and 2018, we paid $2.02 and $0.38, respectively, in dividends and distributions per share and per unit. The $2.02 paid during the three months ended March 31, 2019 represents the per share and unit value of the special dividend and special distribution. The special dividend consisted of $67.1 million in cash, 4.5 million shares of Common Stock and $0.4 million of cash in paid lieu of issuing fractional shares. The special distribution consisted of $72.7 million in cash, 4.8 million common partnership units and $0.4 million of cash paid in lieu of issuing fractional units.

Earnings and Dividends per Share and Unit

Aimco and the Aimco Operating Partnership calculate basic earnings per common share and basic earnings per common unit based on the weighted average number of shares of Common Stock and common partnership units and participating securities outstanding, and calculate diluted earnings per share and diluted earnings per unit taking into consideration dilutive common stock and common partnership unit equivalents and dilutive convertible securities outstanding during the period.

Our common stock and common partnership unit equivalents include options to purchase shares of Common Stock, which, if exercised, would result in Aimco’s issuance of additional shares and the Aimco Operating Partnership’s issuance to Aimco of additional common partnership units equal to the number of shares purchased under the options. These equivalents also include unvested total stockholder return, or TSR, restricted stock awards that do not meet the definition of participating securities, which would result in an increase in the number of shares of Common Stock and common partnership units outstanding equal to the number of shares that vest. The dilutive effect of these securities was 0.2 million and 0.1 million shares and 0.3 million and 0.1 million units for the three months ended March 31, 2019 and 2018, respectively. Securities with dilutive effect are included in the denominator for calculating diluted earnings per share and per unit during these periods. There were no shares and 0.2 million potential shares, and 0.4 million and 0.2 million potential units not dilutive and excluded from the denominator for calculating diluted earnings per share and per unit, respectively, for both the three months ended March 31, 2019 and 2018.

Our time-based restricted stock awards receive dividends similar to shares of Common Stock and common partnership units prior to vesting, and our TSR long-term incentive partnership units receive a percentage of the distributions paid to common partnership units prior to vesting. These dividends and distributions are not forfeited if the awards fail to vest. Therefore, the unvested shares and units related to these awards are participating securities. The effect of participating securities is included in basic and diluted earnings per share and unit computations using the two-class method of allocating distributed and undistributed earnings when the two-class method is more dilutive than the treasury method. There were 0.2 million and 0.3 million unvested restricted participating shares and 0.2 million and 0.3 million unvested restricted participating units, for the three months ended March 31, 2019 and 2018, respectively.

The Aimco Operating Partnership has various classes of preferred OP Units, which may be redeemed at the holders’ option. The Aimco Operating Partnership may redeem these units for cash, or at its option, shares of Common Stock. As of March 31, 2019, these preferred OP Units were potentially redeemable for approximately 2.0 million shares of Common Stock (based on the period end market price), or cash. The Aimco Operating Partnership has a redemption policy that requires cash settlement of redemption requests for the preferred OP Units, subject to limited exceptions. Accordingly, we have excluded these securities from earnings per share and unit computations and we expect to exclude them in future periods.

During the three months ended March 31, 2019 and 2018, we paid $2.02 and $0.38, respectively, in dividends and distributions per share and per unit. The $2.02 paid during the three months ended March 31, 2019 represents the per share and unit value of the special dividend and special distribution. The special dividend consisted of $67.1 million in cash, 4.5 million shares of Common Stock and $0.4 million of cash in paid lieu of issuing fractional shares. The special distribution consisted of $72.7 million in cash, 4.8 million common partnership units and $0.4 million of cash paid in lieu of issuing fractional units.