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Stock Plans and Share-Based Compensation - Narrative (Details) |  |  |  | 8 Months Ended | 12 Months Ended
--- | --- | --- | --- | --- | ---
May 31, 2018 USD ($) shares | Dec. 16, 2017 shares | Mar. 06, 2017 $ / shares shares | Dec. 31, 2018 USD ($) plan shares | Dec. 31, 2018 USD ($) plan employee $ / shares shares | Dec. 31, 2017 $ / shares shares | Dec. 30, 2016 $ / shares
Chief Executive Officer |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |
Stock options granted (in shares) |  |  | 9,000,000 |  |  |  |
Fair value of stock options granted (in dollars per share) | $ / shares |  |  | $ 12.88 |  |  |  |
Options forfeited (in shares) |  | 9,000,000 |  |  |  |  |
Non-management Directors |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |
Annual retainer to be paid to non-management directors, common stock option | $ |  |  |  |  | $ 150,000 |  |
Chairman |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |
Annual grant of common stock amount | $ |  |  |  |  | 250,000 |  |
Performance Units |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |
Unrecognized compensation cost | $ |  |  |  | $ 38,000,000 | $ 38,000,000 |  |
Expected weighted average period of recognition for unrecognized compensation cost (in years) |  |  |  |  | 2 years |  |
Expected life (in years) |  |  |  |  | 2 years 10 months 24 days |  |
Restricted Stock Units and Awards |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |
Award performance period |  |  |  |  | 3 years |  |
Restricted Stock |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |
Award performance period |  |  |  |  | 5 years |  |
Unrecognized compensation cost | $ |  |  |  | 11,000,000 | $ 11,000,000 |  |
Expected weighted average period of recognition for unrecognized compensation cost (in years) |  |  |  |  | 2 years |  |
Stock Options |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |
Unrecognized compensation cost | $ |  |  |  | $ 13,000,000 | $ 13,000,000 |  |
Expected weighted average period of recognition for unrecognized compensation cost (in years) |  |  |  |  | 2 years |  |
Expected life (in years) |  |  |  |  | 6 years 6 months | 6 years 3 months | 6 years 6 months
Stock options granted (in shares) |  |  |  |  | 1,009,000 |  |
Fair value of stock options granted (in dollars per share) | $ / shares |  |  |  |  | $ 14.65 | $ 12.84 | $ 4.68
Number of options exercised in period (in shares) |  |  |  |  | 330,000 |  |
Nonvested stock options (in shares) |  |  |  | 4,673,000 | 4,673,000 | 4,163,000 |
Stock Options | Chief Executive Officer |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |
Award term |  |  | 10 years |  |  |  |
LITP |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |
Award performance period |  |  |  |  | 3 years |  |
LITP | Minimum |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |
Payout range (as a percent) |  |  |  |  | 0.00% |  |
LITP | Maximum |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |
Payout range (as a percent) |  |  |  |  | 200.00% |  |
LITP | Performance Units |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |
Performance unit equivalent of CSX stock (in shares) |  |  |  |  | 1 |  |
LITP | Restricted Stock |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |
Performance unit equivalent of CSX stock (in shares) |  |  |  |  | 1 |  |
LITP | Stock Options |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |
Option requisite service period |  |  |  |  | 3 years |  |
Award term |  |  |  |  | 10 years |  |
2016-2018 LTIP | Performance Units |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |
Award performance period |  |  |  |  | 3 years |  |
Number of plans | plan |  |  |  | 3 | 3 |  |
Payout percentage cumulative period |  |  |  |  | 3 years |  |
Percentage payout on operating ratio |  |  |  |  | 50.00% |  |
Percentage payout on average return on assets |  |  |  |  | 50.00% |  |
2016-2018 LTIP | Performance Units | Certain Executive Officers |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |
Percentage of payout subject to reduction (up to) |  |  |  |  | 30.00% |  |
2017-2019 LTIP | Performance Units |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |
Award performance period |  |  |  |  | 3 years |  |
Payout percentage cumulative period |  |  |  |  | 3 years |  |
Percentage payout on operating ratio |  |  |  |  | 50.00% |  |
Percentage payout on average return on assets |  |  |  |  | 50.00% |  |
2017-2019 LTIP | Performance Units | Certain Executive Officers |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |
Percentage of payout subject to reduction (up to) |  |  |  |  | 30.00% |  |
2018-2020 LTIP | Performance Units |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |
Award performance period |  |  |  |  | 3 years |  |
Percentage payout on operating ratio |  |  |  |  | 50.00% |  |
2018-2020 LTIP | Performance Units | Certain Executive Officers |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |
Percentage of payout subject to reduction (up to) |  |  |  |  | 25.00% |  |
2018-2020 LTIP | Performance Units | Maximum | Certain Executive Officers |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |
Payout range (as a percent) |  |  |  |  | 200.00% |  |
Equity Award Modifications |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |
Number of employees impacted (employees) | employee |  |  |  |  | 75 |  |
Share-based compensation expense revaluation of awards | $ |  |  |  |  | $ 39,000,000 |  |
Non-management Directors |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |
Annual retainer to be paid to non-management directors, cash option | $ |  |  |  |  | $ 100,000 |  |
ESPP | Employee Stock |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |
Number of registered shares of common stock that my be issued pursuant to plan (in shares) | 4,000,000 |  |  |  |  |  |
Maximum value of stocks purchased by employee, after tax | $ | $ 25,000 |  |  |  |  |  |
Percentage of share closing market price |  |  |  | 85.00% |  |  |
Share offering period | 6 months |  |  |  |  |  |
Number of shares issued under the plan (in shares) |  |  |  | 0 |  |  |
ESPP | Employee Stock | Minimum |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |
Employee contribution percentage | 1.00% |  |  |  |  |  |
ESPP | Employee Stock | Maximum |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |
Employee contribution percentage | 10.00% |  |  |  |  |  |

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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
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