Stock-Based Compensation Stock-Based Compensation (Notes)	3 Months Ended
Mar. 31, 2018
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Disclosure of Compensation Related Costs, Share-based Payments [Text Block]	Stock-Based Compensation The Company has an equity compensation plan, the M/I Homes, Inc. 2009 Long-Term Incentive Plan (the “2009 LTIP”), which has been amended from time to time. The 2009 LTIP was approved by our shareholders and is administered by the Compensation Committee of our Board of Directors. Under the 2009 LTIP, the Company is permitted to grant (1) nonqualified stock options to purchase common shares, (2) incentive stock options to purchase common shares, (3) stock appreciation rights, (4) restricted common shares, (5) other stock-based awards – awards that are valued in whole or in part by reference to, or otherwise based on, the fair market value of the common shares, and (6) cash-based awards to its officers, employees, non-employee directors and other eligible participants. Subject to certain adjustments, the plan authorizes awards to officers, employees, non-employee directors and other eligible participants for up to 3,900,000 common shares, of which 983,845 remain available for grant at March 31, 2018. The 2009 LTIP replaced the M/I Homes, Inc. 1993 Stock Incentive Plan as Amended (the “1993 Plan”), which expired by its terms on April 22, 2009. Awards outstanding under the 1993 Plan remain in effect in accordance with their respective terms. Stock Options On February 15, 2018, the Company awarded certain of its employees 431,500 (in the aggregate) nonqualified stock options at an exercise price of $31.93 (the closing price of our common shares on the New York Stock Exchange on such date) and a fair value of $11.31 that vest ratably over a five-year period. Total stock-based compensation expense related to stock option awards that has been charged against income relating to the 2009 LTIP was $1.0 million for both the three months ended March 31, 2018 and 2017. As of March 31, 2018, there was a total of $10.6 million of unrecognized compensation expense related to unvested stock option awards that will be recognized as stock-based compensation expense as the awards vest over a weighted average period of 2.2 years for the service awards. Performance Share Unit Awards On February 15, 2018, February 8, 2017 and February 16, 2016, the Company awarded its executive officers (in the aggregate) a target number of performance share units (“PSU’s”) equal to 46,444, 57,110 and 79,108 PSU’s, respectively. Each PSU represents a contingent right to receive one common share of the Company if vesting is satisfied at the end of a three-year performance period (the “Performance Period”). The ultimate number of PSU’s that will vest and be earned, if any, after the completion of the Performance Period, is based on (1) (a) the Company’s cumulative pre-tax income from operations, excluding extraordinary items, as defined in the underlying award agreements with the executive officers, over the Performance Period (weighted 80%) (the “Performance Condition”), and (b) the Company’s relative total shareholder return over the Performance Period compared to the total shareholder return of a peer group of other publicly-traded homebuilders (weighted 20%) (the “Market Condition”) and (2) the participant’s continued employment through the end of the Performance Period, except in the case of termination due to death, disability or retirement or involuntary termination without cause by the Company. The number of PSU’s that vest may increase by up to 50% from the target number based on levels of achievement of the above criteria as set forth in the applicable award agreements and decrease to zero if the Company fails to meet the minimum performance levels for both of the above criteria. If the Company achieves the minimum performance levels for both of the above criteria, 50% of the target number of PSU’s will vest and be earned. Any portion of PSU’s that does not vest at the end of the Performance Period will be forfeited. Additionally, the PSU’s have no dividend or voting rights during the Performance Period. The grant date fair value of the portion of the PSU’s subject to the Performance Condition and the Market Condition component was $31.93 and $33.57 for the 2018 PSU’s, respectively, $23.34 and $19.69 for the 2017 PSU’s, respectively, and $16.85 and $15.75 for the 2016 PSU’s, respectively. In accordance with ASC 718, for the portion of the PSU’s subject to a Market Condition, stock-based compensation expense is derived using the Monte Carlo simulation methodology and is recognized ratably over the service period regardless of whether or not the attainment of the Market Condition is probable. Therefore, the Company recognized less than $0.1 million in stock-based compensation expense during the first quarter of 2018 related to the Market Condition portion of the 2018, 2017 and 2016 PSU awards. There was a total of $0.4 million of unrecognized stock-based compensation expense related to the Market Condition portion of the 2018, 2017 and 2016 PSU awards as of March 31, 2018. For the portion of the PSU’s subject to the Performance Condition, we recognize stock-based compensation expense on a straight-line basis over the Performance Period based on the probable outcome of the related Performance Condition. Otherwise, stock-based compensation expense recognition is deferred until probability is attained and a cumulative stock-based compensation expense adjustment is recorded and recognized ratably over the remaining service period. The Company reassesses the probability of the satisfaction of the Performance Condition on a quarterly basis, and stock-based compensation expense is adjusted based on the portion of the requisite service period that has passed. As of March 31, 2018, the Company had not recognized any stock-based compensation expense related to the Performance Condition portion of the 2018 or the 2017 PSU awards. If the Company achieves the minimum performance levels for the Performance Conditions to be met for the 2018 and the 2017 awards, the Company would record unrecognized stock-based compensation expense of $1.0 million as of March 31, 2018, for which $0.3 million would be immediately recognized had attainment been probable at March 31, 2018. The Company recognized less than $0.1 million of stock-based compensation expense related to the Performance Condition portion of the 2016 PSU awards during the first quarter of 2018 based on the probability of attaining the performance condition. The Company has $0.1 million of unrecognized stock-based compensation expense for the 2016 PSU awards as of March 31, 2018.

Stock-Based Compensation

The Company has an equity compensation plan, the M/I Homes, Inc. 2009 Long-Term Incentive Plan (the “2009 LTIP”), which has been amended from time to time. The 2009 LTIP was approved by our shareholders and is administered by the Compensation Committee of our Board of Directors. Under the 2009 LTIP, the Company is permitted to grant (1) nonqualified stock options to purchase common shares, (2) incentive stock options to purchase common shares, (3) stock appreciation rights, (4) restricted common shares, (5) other stock-based awards – awards that are valued in whole or in part by reference to, or otherwise based on, the fair market value of the common shares, and (6) cash-based awards to its officers, employees, non-employee directors and other eligible participants. Subject to certain adjustments, the plan authorizes awards to officers, employees, non-employee directors and other eligible participants for up to 3,900,000 common shares, of which 983,845 remain available for grant at March 31, 2018.

The 2009 LTIP replaced the M/I Homes, Inc. 1993 Stock Incentive Plan as Amended (the “1993 Plan”), which expired by its terms on April 22, 2009. Awards outstanding under the 1993 Plan remain in effect in accordance with their respective terms.

Stock Options

On February 15, 2018, the Company awarded certain of its employees 431,500 (in the aggregate) nonqualified stock options at an exercise price of $31.93 (the closing price of our common shares on the New York Stock Exchange on such date) and a fair value of $11.31 that vest ratably over a five-year period. Total stock-based compensation expense related to stock option awards that has been charged against income relating to the 2009 LTIP was $1.0 million for both the three months ended March 31, 2018 and 2017. As of March 31, 2018, there was a total of $10.6 million of unrecognized compensation expense related to unvested stock option awards that will be recognized as stock-based compensation expense as the awards vest over a weighted average period of 2.2 years for the service awards.

Performance Share Unit Awards

On February 15, 2018, February 8, 2017 and February 16, 2016, the Company awarded its executive officers (in the aggregate) a target number of performance share units (“PSU’s”) equal to 46,444, 57,110 and 79,108 PSU’s, respectively. Each PSU represents a contingent right to receive one common share of the Company if vesting is satisfied at the end of a three-year performance period (the “Performance Period”). The ultimate number of PSU’s that will vest and be earned, if any, after the completion of the Performance Period, is based on (1) (a) the Company’s cumulative pre-tax income from operations, excluding extraordinary items, as defined in the underlying award agreements with the executive officers, over the Performance Period (weighted 80%) (the “Performance Condition”), and (b) the Company’s relative total shareholder return over the Performance Period compared to the total shareholder return of a peer group of other publicly-traded homebuilders (weighted 20%) (the “Market Condition”) and (2) the participant’s continued employment through the end of the Performance Period, except in the case of termination due to death, disability or retirement or involuntary termination without cause by the Company. The number of PSU’s that vest may increase by up to 50% from the target number based on levels of achievement of the above criteria as set forth in the applicable award agreements and decrease to zero if the Company fails to meet the minimum performance levels for both of the above criteria. If the Company achieves the minimum performance levels for both of the above criteria, 50% of the target number of PSU’s will vest and be earned. Any portion of PSU’s that does not vest at the end of the Performance Period will be forfeited. Additionally, the PSU’s have no dividend or voting rights during the Performance Period.

The grant date fair value of the portion of the PSU’s subject to the Performance Condition and the Market Condition component was $31.93 and $33.57 for the 2018 PSU’s, respectively, $23.34 and $19.69 for the 2017 PSU’s, respectively, and $16.85 and $15.75 for the 2016 PSU’s, respectively. In accordance with ASC 718, for the portion of the PSU’s subject to a Market Condition, stock-based compensation expense is derived using the Monte Carlo simulation methodology and is recognized ratably over the service period regardless of whether or not the attainment of the Market Condition is probable. Therefore, the Company recognized less than $0.1 million in stock-based compensation expense during the first quarter of 2018 related to the Market Condition portion of the 2018, 2017 and 2016 PSU awards. There was a total of $0.4 million of unrecognized stock-based compensation expense related to the Market Condition portion of the 2018, 2017 and 2016 PSU awards as of March 31, 2018.

For the portion of the PSU’s subject to the Performance Condition, we recognize stock-based compensation expense on a straight-line basis over the Performance Period based on the probable outcome of the related Performance Condition. Otherwise, stock-based compensation expense recognition is deferred until probability is attained and a cumulative stock-based compensation expense adjustment is recorded and recognized ratably over the remaining service period. The Company reassesses the probability of the satisfaction of the Performance Condition on a quarterly basis, and stock-based compensation expense is adjusted based on the portion of the requisite service period that has passed. As of March 31, 2018, the Company had not recognized any stock-based compensation expense related to the Performance Condition portion of the 2018 or the 2017 PSU awards. If the Company achieves the minimum performance levels for the Performance Conditions to be met for the 2018 and the 2017 awards, the Company would record unrecognized stock-based compensation expense of $1.0 million as of March 31, 2018, for which $0.3 million would be immediately recognized had attainment been probable at March 31, 2018. The Company recognized less than $0.1 million of stock-based compensation expense related to the Performance Condition portion of the 2016 PSU awards during the first quarter of 2018 based on the probability of attaining the performance condition. The Company has $0.1 million of unrecognized stock-based compensation expense for the 2016 PSU awards as of March 31, 2018.