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EMPLOYEE BENEFITS - Schedule of Asset Category (Details) - USD ($) $ in Millions | 12 Months Ended |
--- | --- | ---
Dec. 31, 2023 | Dec. 31, 2022 | Dec. 31, 2021
Pension and SERP |  |  |
Defined Contribution Plan Disclosure [Line Items] |  |  |
Fair value of pension plan assets | $ 5,775.0 | $ 5,806.4 | $ 6,495.5
Uncategorized | 4,776.8 | 5,116.9 |
Pension and SERP | Total Assets Before 401 |  |  |
Defined Contribution Plan Disclosure [Line Items] |  |  |
Fair value of pension plan assets | 6,019.9 | 6,062.0 |
Pension and SERP | Equity Securities |  |  |
Defined Contribution Plan Disclosure [Line Items] |  |  |
Fair value of pension plan assets | 1,227.0 | 1,509.9 |
Uncategorized | 853.0 | 1,102.2 |
Pension and SERP | Fixed Income |  |  |
Defined Contribution Plan Disclosure [Line Items] |  |  |
Fair value of pension plan assets | 2,211.9 | 1,954.4 |
Uncategorized | 1,516.4 | 1,598.8 |
Pension and SERP | Private Equity |  |  |
Defined Contribution Plan Disclosure [Line Items] |  |  |
Fair value of pension plan assets | 1,685.3 | 1,684.9 |
Uncategorized | 1,685.3 | 1,684.9 |
Pension and SERP | Real Assets |  |  |
Defined Contribution Plan Disclosure [Line Items] |  |  |
Fair value of pension plan assets | 895.7 | 912.8 |
Uncategorized | 722.1 | 731.0 |
Pension and SERP | 401 PBOP Assets |  |  |
Defined Contribution Plan Disclosure [Line Items] |  |  |
Fair value of pension plan assets | (244.9) | (255.6) |
Pension and SERP | Level 1 |  |  |
Defined Contribution Plan Disclosure [Line Items] |  |  |
Fair value of pension plan assets | 902.2 | 866.6 |
Pension and SERP | Level 1 | Equity Securities |  |  |
Defined Contribution Plan Disclosure [Line Items] |  |  |
Fair value of pension plan assets | 374.0 | 407.7 |
Pension and SERP | Level 1 | Fixed Income |  |  |
Defined Contribution Plan Disclosure [Line Items] |  |  |
Fair value of pension plan assets | 354.6 | 277.1 |
Pending redemption settlements | 31.0 | 138.0 |
Pension and SERP | Level 1 | Private Equity |  |  |
Defined Contribution Plan Disclosure [Line Items] |  |  |
Fair value of pension plan assets | 0.0 | 0.0 |
Pension and SERP | Level 1 | Real Assets |  |  |
Defined Contribution Plan Disclosure [Line Items] |  |  |
Fair value of pension plan assets | 173.6 | 181.8 |
Pension and SERP | Level 2 |  |  |
Defined Contribution Plan Disclosure [Line Items] |  |  |
Fair value of pension plan assets | 340.9 | 78.5 |
Pension and SERP | Level 2 | Equity Securities |  |  |
Defined Contribution Plan Disclosure [Line Items] |  |  |
Fair value of pension plan assets | 0.0 | 0.0 |
Pension and SERP | Level 2 | Fixed Income |  |  |
Defined Contribution Plan Disclosure [Line Items] |  |  |
Fair value of pension plan assets | 340.9 | 78.5 |
Pension and SERP | Level 2 | Private Equity |  |  |
Defined Contribution Plan Disclosure [Line Items] |  |  |
Fair value of pension plan assets | 0.0 | 0.0 |
Pension and SERP | Level 2 | Real Assets |  |  |
Defined Contribution Plan Disclosure [Line Items] |  |  |
Fair value of pension plan assets | 0.0 | 0.0 |
PBOP |  |  |
Defined Contribution Plan Disclosure [Line Items] |  |  |
Fair value of pension plan assets | 1,024.4 | 970.1 | $ 1,138.3
Uncategorized | 493.5 | 431.7 |
PBOP | Total Assets Before 401 |  |  |
Defined Contribution Plan Disclosure [Line Items] |  |  |
Fair value of pension plan assets | 779.5 | 714.5 |
PBOP | Equity Securities |  |  |
Defined Contribution Plan Disclosure [Line Items] |  |  |
Fair value of pension plan assets | 351.2 | 336.7 |
Uncategorized | 212.1 | 183.5 |
PBOP | Fixed Income |  |  |
Defined Contribution Plan Disclosure [Line Items] |  |  |
Fair value of pension plan assets | 236.2 | 199.5 |
Uncategorized | 159.8 | 141.1 |
PBOP | Private Equity |  |  |
Defined Contribution Plan Disclosure [Line Items] |  |  |
Fair value of pension plan assets | 87.7 | 70.9 |
Uncategorized | 87.7 | 70.9 |
PBOP | Real Assets |  |  |
Defined Contribution Plan Disclosure [Line Items] |  |  |
Fair value of pension plan assets | 104.4 | 107.4 |
Uncategorized | 33.9 | 36.2 |
PBOP | 401 PBOP Assets |  |  |
Defined Contribution Plan Disclosure [Line Items] |  |  |
Fair value of pension plan assets | 244.9 | 255.6 |
PBOP | Level 1 |  |  |
Defined Contribution Plan Disclosure [Line Items] |  |  |
Fair value of pension plan assets | 243.0 | 242.6 |
PBOP | Level 1 | Equity Securities |  |  |
Defined Contribution Plan Disclosure [Line Items] |  |  |
Fair value of pension plan assets | 139.1 | 153.2 |
PBOP | Level 1 | Fixed Income |  |  |
Defined Contribution Plan Disclosure [Line Items] |  |  |
Fair value of pension plan assets | 33.4 | 18.2 |
PBOP | Level 1 | Private Equity |  |  |
Defined Contribution Plan Disclosure [Line Items] |  |  |
Fair value of pension plan assets | 0.0 | 0.0 |
PBOP | Level 1 | Real Assets |  |  |
Defined Contribution Plan Disclosure [Line Items] |  |  |
Fair value of pension plan assets | 70.5 | 71.2 |
PBOP | Level 2 |  |  |
Defined Contribution Plan Disclosure [Line Items] |  |  |
Fair value of pension plan assets | 43.0 | 40.2 |
PBOP | Level 2 | Equity Securities |  |  |
Defined Contribution Plan Disclosure [Line Items] |  |  |
Fair value of pension plan assets | 0.0 | 0.0 |
PBOP | Level 2 | Fixed Income |  |  |
Defined Contribution Plan Disclosure [Line Items] |  |  |
Fair value of pension plan assets | 43.0 | 40.2 |
PBOP | Level 2 | Private Equity |  |  |
Defined Contribution Plan Disclosure [Line Items] |  |  |
Fair value of pension plan assets | 0.0 | 0.0 |
PBOP | Level 2 | Real Assets |  |  |
Defined Contribution Plan Disclosure [Line Items] |  |  |
Fair value of pension plan assets | $ 0.0 | $ 0.0 |

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