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Stock-Based Compensation (Tables) | 12 Months Ended
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Dec. 31, 2023
Share-Based Payment Arrangement [Abstract] |
Schedule of Stock-based Compensation Plans | The table below summarizes certain data for our stock-based compensation plans (in millions):
| Successor |  |  | Predecessor
| Fiscal Year Ended December 31, 2023 |  | Fiscal Year Ended December 31, 2022 |  | From October 20, 2021 through December 31, 2021 |  |  | From July 1, 2021 through October 19, 2021
Stock-based compensation expense - Profits Interests | $ | 13.3 |  |  | $ | 25.2 |  |  | $ | 5.3 |  |  |  | $ | 9.3 |
Stock-based compensation expense - Omnibus Plan (excluding directors) | $ | 7.6 |  |  | $ | 5.5 |  |  | $ | — |  |  |  | $ | — |
Stock-based compensation expense - Omnibus Plan (directors) | $ | 0.7 |  |  | $ | 0.7 |  |  | $ | — |  |  |  | $ | — |
Tax benefit for stock-based compensation (1) | $ | 2.4 |  |  | $ | 1.0 |  |  | $ | — |  |  |  | $ | — |
(1) Tax benefit (expense) was zero related to Profits Interests expense for the years ended December 31, 2023 and 2022, Successor Stub Period from October 20, 2021 through December 31, 2021, and Predecessor Stub Period from July 1, 2021 through October 19, 2021.
Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions | The fair value of the market condition PSUs is determined using a Monte Carlo simulation model on the grant date with the following assumptions:
| Successor
| March 29, 2023 |  | April 1, 2022 |  | December 27, 2021
MIR Stock Price | $ | 8.06 |  |  | $ | 8.13 |  |  | $ | 10.70 |
Expected volatility(1) | 45.30 | % |  | 45.32 | % |  | 41.12 | %
Risk-free interest rate(2) | 3.92 | % |  | 2.61 | % |  | 0.98 | %
Dividend yield | 0.00 | % |  | 0.00 | % |  | 0.00 | %
Fair value | $ | 11.83 |  |  | $ | 11.69 |  |  | $ | 7.91 |
(1) Expected volatility is based on historical volatilities from a group of comparable entities for a time period similar to that of the expected term. (2) The risk-free rate is based on an average of U.S. Treasury yields in effect at the time of grant corresponding with the expected term. The fair value of the Profits Interests are estimated based on a valuation model using Monte Carlo simulations, for the $12, $14, and $16 per share performance vesting conditions, with the following assumptions:
Cost of equity (1) | 8.5 | %
Risk-free interest rate (2) | 0.1 | %
Expected volatility (3) | 30.0 | %
Expected term (in years) (4) | 5
Average fair value of all profits interests | $ | 6.90 |
(1) Cost of equity based on a group of comparable entities (2) The risk-free rate is based on an average of U.S. Treasury yields in effect at the time of grant corresponding with the expected term. (3) Expected volatility is based on historical volatilities from a group of comparable entities for a time period similar to that of the expected term and the expected term. (4) Expected term is based on probability and expected timing of market events. The fair value of the Predecessor Shares was estimated using the Black-Scholes option-pricing model, with the following assumptions:
|  | Predecessor
|  | June 30, 2020
Dividend yield |  | 0.0 | %
Risk-free interest rate (1) |  | 0.2 | %
Expected volatility (2) |  | 55.7 | %
Expected term (in years) (3) |  | 3
Fair value |  | $ | 0.37 |
(1) The risk-free rate is based on an average of U.S. Treasury yields in effect at the time of grant corresponding with the expected term. (2) Expected volatility is based on historical volatilities from a group of comparable entities for a time period similar to that of the expected term and the expected term. (3) Expected term is based on probability and expected timing of market events.
Activity of RSUs, PSUs, and Director RSUs | Activity of our RSUs, PSUs, and Director RSUs is as follows:
| RSUs |  | PSUs |  | Director RSUs
| Quantity |  | Weighted average grant date fair value |  | Quantity |  | Weighted average grant date fair value |  | Quantity |  | Weighted average grant date fair value
Beginning balance at Business Combination | — |  |  | $ | — |  |  | — |  |  | $ | — |  |  | — |  |  | $ | — |
Awards granted | 974,775 |  |  | 10.48 |  |  | 229,006 |  |  | 9.20 |  |  | 34,902 |  |  | 10.48 |
Awards vested | — |  |  | — |  |  | — |  |  | — |  |  | — |  |  | — |
Awards forfeited | — |  |  | — |  |  | — |  |  | — |  |  | — |  |  | — |
Total awards outstanding at December 31, 2021 | 974,775 |  |  | $ | 10.48 |  |  | 229,006 |  |  | $ | 9.20 |  |  | 34,902 |  |  | $ | 10.48 |
Awards granted | 1,005,100 |  |  | 8.05 |  |  | 187,356 |  |  | 9.88 |  |  | 94,811 |  |  | 6.65 |
Awards vested | 225,186 |  |  | 10.48 |  |  | — |  |  | — |  |  | 80,779 |  |  | 8.29 |
Awards forfeited | 95,663 |  |  | 9.65 |  |  | 4,956 |  |  | 9.88 |  |  | — |  |  | — |
Total awards outstanding at December 31, 2022 | 1,659,026 |  |  | $ | 9.05 |  |  | 411,406 |  |  | $ | 9.50 |  |  | 48,934 |  |  | $ | 6.68 |
Awards granted | 729,829 |  |  | 8.05 |  |  | 322,323 |  |  | 9.42 |  |  | 82,950 |  |  | 7.89 |
Awards vested | 500,603 |  |  | 9.06 |  |  | — |  |  | — |  |  | 90,409 |  |  | 7.24 |
Awards forfeited | 242,173 |  |  | 8.55 |  |  | 27,193 |  |  | 9.93 |  |  | — |  |  | — |
Total awards outstanding at December 31, 2023 | 1,646,079 |  |  | $ | 8.68 |  |  | 706,536 |  |  | $ | 9.45 |  |  | 41,475 |  |  | $ | 7.89 |
Schedule of Unrecognized Compensation Cost | Unrecognized compensation cost and weighted average periods remaining for non-vested awards as of December 31, 2023 are as follows (dollars in millions):
| Successor
| As of December 31, 2023 |  | Weighted average period remaining for non-vested awards as of December 31, 2023
Unrecognized compensation cost |  |  |
RSUs | $ | 11.4 |  |  | 1.2 years
PSUs | 3.2 |  |  | 1.2 years
Director RSUs | 0.3 |  |  | 4 months
Total unrecognized compensation cost | $ | 14.9 |  |  |
Share-based Payment Arrangement, Activity | A summary of restricted stock activity within the Company’s equity plans and changes for the years ended June 30, 2021 and the Predecessor Stub Period, is as follows:
| Shares (in millions) |  | Weighted Average Grant- Date Fair Value |  | Total Fair Value (in millions)
Restricted Stock Awards |  |  |  |  |
Nonvested at June 30, 2021 | 0.2 |  |  | $ | 0.27 |  |  | $ | — |
Granted | — |  |  | — |  |  | — |
Vested | (0.2) |  |  | 0.27 |  |  | — |
Repurchased | — |  |  | — |  |  | — |
Nonvested at October 19, 2021 | — |  |  | $ | — |  |  | $ | — |

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