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Share-Based Compensation (Tables) | 12 Months Ended
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Mar. 31, 2018
Disclosure of Compensation Related Costs, Share-based Payments [Abstract] |
Schedule of components of share-based compensation expense and related tax benefits | The components of share-based compensation expense and related tax benefits are as follows:
| Years Ended March 31,
(In millions) | 2018 |  | 2017 |  | 2016
Restricted stock unit awards (1) | $ | 46 |  |  | $ | 79 |  |  | $ | 88 |
Stock options | 14 |  |  | 24 |  |  | 22 |
Employee stock purchase plan | 9 |  |  | 12 |  |  | 13 |
Share-based compensation expense (2) | 69 |  |  | 115 |  |  | 123 |
Tax benefit for share-based compensation expense (3) | (28 | ) |  | (92 | ) |  | (41 | )
Share-based compensation expense, net of tax | $ | 41 |  |  | $ | 23 |  |  | $ | 82 |
(1) | Includes compensation expense recognized for RSUs, PeRSUs and TSRUs. Our TSRUs were awarded beginning in 2015.
(2) | 2016 includes non-cash credits of $14 million representing the reversal of previously recognized share-based compensation expense, which was recorded due to employee terminations associated with the March 2016 Cost Alignment Plan.
(3) | Income tax benefit is computed using the tax rates of applicable tax jurisdictions. Additionally, a portion of pre-tax compensation expense is not tax-deductible. Income tax expense for 2018 and 2017 included discrete income tax benefits of $8 million and $54 million related to the adoption of the amended accounting guidance on share-based compensation.
Schedule of weighted-average assumptions used to estimate the fair value | The weighted-average assumptions used to estimate the fair value of TSRUs are as follows:
| Years Ended March 31,
| 2018 |  | 2017 |  | 2016
Expected stock price volatility | 29% |  | 23% |  | 18%
Expected dividend yield | 0.8% |  | 0.7% |  | 0.4%
Risk-free interest rate | 1.5% |  | 1.1% |  | 0.9%
Expected life (in years) | 3 |  | 3 |  | 3
Weighted-average assumptions used to estimate the fair value of employee stock options were as follows:
| Years Ended March 31,
| 2018 |  | 2017 |  | 2016
Expected stock price volatility | 25% |  | 21% |  | 21%
Expected dividend yield | 0.8% |  | 0.7% |  | 0.4%
Risk-free interest rate | 1.7% |  | 1.1% |  | 1.4%
Expected life (in years) | 4.5 |  | 4 |  | 4
Summary of options outstanding | The following is a summary of stock options outstanding at March 31, 2018:
|  | Options Outstanding |  | Options Exercisable
Range of Exercise Prices |  | Number of Options Outstanding at Year End (In millions) |  | Weighted- Average Remaining Contractual Life (Years) |  | Weighted- Average Exercise Price |  | Number of Options Exercisable at Year End (In millions) |  | Weighted- Average Exercise Price
$ | 76.55 |  | – | $ | 158.24 |  |  | 1 |  | 2 |  | $ | 108.17 |  |  | 1 |  | $ | 106.05 |
158.25 |  | – | 239.93 |  |  | 2 |  | 4 |  | 190.18 |  |  | 1 |  | 199.13 |
|  |  |  | 3 |  |  |  |  |  | 2 |  |
Summary of stock option activity | The following table summarizes stock option activity during 2018:
(In millions, except per share data) | Shares |  | Weighted- Average Exercise Price |  | Weighted- Average Remaining Contractual Term (Years) |  | Aggregate Intrinsic Value (2)
Outstanding, March 31, 2017 | 4 |  | $ | 145.76 |  |  | 4 |  | $ | 97 |
Granted | 1 |  | 157.45 |  |  |  |  |
Cancelled | (1) |  | 180.79 |  |  |  |  |
Exercised | (1) |  | 86.95 |  |  |  |  |
Outstanding, March 31, 2018 | 3 |  | $ | 161.27 |  |  | 4 |  | $ | 36 |
Vested and expected to vest (1) | 3 |  | $ | 160.28 |  |  | 4 |  | $ | 35 |
Vested and exercisable, March 31, 2018 | 2 |  | 147.76 |  |  | 2 |  | 35 |
(1) | The number of options expected to vest takes into account an estimate of expected forfeitures.
(2) | The intrinsic value is calculated as the difference between the period-end market price of the Company’s common stock and the exercise price of “in-the-money” options.
Summary of data related to stock option activity | The following table provides data related to stock option activity:
| Years Ended March 31,
(In millions, except per share data) | 2018 |  | 2017 |  | 2016
Weighted-average grant date fair value per stock option | $ | 34.24 |  |  | $ | 32.19 |  |  | $ | 44.04 |
Aggregate intrinsic value on exercise | $ | 60 |  |  | $ | 97 |  |  | $ | 107 |
Cash received upon exercise | $ | 77 |  |  | $ | 54 |  |  | $ | 47 |
Tax benefits realized related to exercise | $ | 22 |  |  | $ | 38 |  |  | $ | 42 |
Total fair value of stock options vested | $ | 20 |  |  | $ | 18 |  |  | $ | 18 |
Total compensation cost, net of estimated forfeitures, related to unvested stock options not yet recognized, pre-tax | $ | 15 |  |  | $ | 21 |  |  | $ | 20 |
Weighted-average period in years over which stock option compensation cost is expected to be recognized | 2 |  |  | 2 |  |  | 2 |
Summary of restricted stock unit award activity | The following table summarizes activity for restricted stock unit awards (RSUs, PeRSUs, and TSRUs) during 2018:
(In millions, except per share data) | Shares |  | Weighted- Average Grant Date Fair Value Per Share
Nonvested, March 31, 2017 | 2 |  | $ | 188.54 |
Granted | 1 |  | 159.49 |
Vested | (1) |  | 172.02 |
Nonvested, March 31, 2018 | 2 |  | $ | 176.74 |
Schedule of data related to restricted stock unit award activity | The following table provides data related to restricted stock unit award activity:
| Years Ended March 31,
(In millions) | 2018 |  | 2017 |  | 2016
Total fair value of shares vested | $ | 156 |  |  | $ | 109 |  |  | $ | 104 |
Total compensation cost, net of estimated forfeitures, related to nonvested restricted stock unit awards not yet recognized, pre-tax | $ | 97 |  |  | $ | 99 |  |  | $ | 144 |
Weighted-average period in years over which restricted stock unit award cost is expected to be recognized | 2 |  |  | 2 |  |  | 2 |

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