EMPLOYEE BENEFITS - Schedule of Asset Category (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Pension and SERP
Defined Contribution Plan Disclosure [Line Items]
Fair value of pension plan assets	$ 5,806.4	$ 6,495.5	$ 5,409.2
Uncategorized	5,116.9	5,479.8
Pension and SERP | Total Assets Before 401
Defined Contribution Plan Disclosure [Line Items]
Fair value of pension plan assets	6,062.0	6,794.0
Pension and SERP | Equity securities
Defined Contribution Plan Disclosure [Line Items]
Fair value of pension plan assets	1,509.9	2,107.7
Uncategorized	1,102.2	1,385.2
Pension and SERP | Fixed Income
Defined Contribution Plan Disclosure [Line Items]
Fair value of pension plan assets	1,954.4	2,062.5
Uncategorized	1,598.8	1,689.1
Pension and SERP | Private Equity
Defined Contribution Plan Disclosure [Line Items]
Fair value of pension plan assets	1,684.9	1,702.7
Uncategorized	1,684.9	1,702.7
Pension and SERP | Real Assets
Defined Contribution Plan Disclosure [Line Items]
Fair value of pension plan assets	912.8	921.1
Uncategorized	731.0	702.8
Pension and SERP | 401 PBOP Assets
Defined Contribution Plan Disclosure [Line Items]
Fair value of pension plan assets	(255.6)	(298.5)
Pension and SERP | Level 1
Defined Contribution Plan Disclosure [Line Items]
Fair value of pension plan assets	866.6	1,080.4
Pension and SERP | Level 1 | Equity securities
Defined Contribution Plan Disclosure [Line Items]
Fair value of pension plan assets	407.7	722.5
Pension and SERP | Level 1 | Fixed Income
Defined Contribution Plan Disclosure [Line Items]
Fair value of pension plan assets	277.1	139.6
Pending redemption settlements	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	181.8	218.3
Pension and SERP | Level 2
Defined Contribution Plan Disclosure [Line Items]
Fair value of pension plan assets	78.5	233.8
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	78.5	233.8
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	970.1	1,138.3	$ 1,004.1
Uncategorized	431.7	463.5
PBOP | Total Assets Before 401
Defined Contribution Plan Disclosure [Line Items]
Fair value of pension plan assets	714.5	839.8
PBOP | Equity securities
Defined Contribution Plan Disclosure [Line Items]
Fair value of pension plan assets	336.7	439.7
Uncategorized	183.5	248.3
PBOP | Fixed Income
Defined Contribution Plan Disclosure [Line Items]
Fair value of pension plan assets	199.5	220.4
Uncategorized	141.1	125.5
PBOP | Private Equity
Defined Contribution Plan Disclosure [Line Items]
Fair value of pension plan assets	70.9	58.7
Uncategorized	70.9	58.7
PBOP | Real Assets
Defined Contribution Plan Disclosure [Line Items]
Fair value of pension plan assets	107.4	121.0
Uncategorized	36.2	31.0
PBOP | 401 PBOP Assets
Defined Contribution Plan Disclosure [Line Items]
Fair value of pension plan assets	255.6	298.5
PBOP | Level 1
Defined Contribution Plan Disclosure [Line Items]
Fair value of pension plan assets	242.6	331.1
PBOP | Level 1 | Equity securities
Defined Contribution Plan Disclosure [Line Items]
Fair value of pension plan assets	153.2	191.4
PBOP | Level 1 | Fixed Income
Defined Contribution Plan Disclosure [Line Items]
Fair value of pension plan assets	18.2	49.7
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	71.2	90.0
PBOP | Level 2
Defined Contribution Plan Disclosure [Line Items]
Fair value of pension plan assets	40.2	45.2
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	40.2	45.2
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