EMPLOYEE BENEFIT PLANS (Changes in Benefit Obligations, Fair Value of Plan Assets, and Funded Status of Plan) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Pension Plans
Change in benefit obligation:
Benefit obligation at beginning of year	$ 357.0	$ 353.3
Service cost	48.1	55.6	$ 57.5
Interest cost	17.7	7.9	5.3
Plan amendments	0.0	0.0
Benefit payments	(18.1)	(18.9)
Actuarial loss (gain)	25.0	(40.9)
Projected benefit obligation at end of year	429.7	357.0	353.3
Change in plan assets:
Fair value of plan assets at beginning of year	274.2	306.3
Actual return on plan assets	34.8	(51.0)
Benefits paid	(18.1)	(18.9)
Employer contributions	58.4	37.8
Fair value of plan assets at end of year	349.3	274.2	306.3
Reconciliation of funded status:
Fair value of plan assets at end of year	349.3	274.2	306.3
Less benefit obligations at end of year	429.7	357.0	353.3
Funded status at end of year	(80.4)	(82.8)
Post-Retirement Medical Plan
Change in benefit obligation:
Benefit obligation at beginning of year	13.9	18.2
Service cost	0.5	0.8	1.1
Interest cost	0.7	0.3	0.3
Plan amendments	6.0	0.0
Benefit payments	(1.4)	(1.4)
Actuarial loss (gain)	(0.1)	(4.0)
Projected benefit obligation at end of year	19.6	13.9	18.2
Change in plan assets:
Fair value of plan assets at beginning of year	0.0	0.0
Actual return on plan assets	0.0	0.0
Benefits paid	(1.4)	(1.4)
Employer contributions	1.4	1.4
Fair value of plan assets at end of year	0.0	0.0	0.0
Reconciliation of funded status:
Fair value of plan assets at end of year	0.0	0.0	0.0
Less benefit obligations at end of year	19.6	13.9	$ 18.2
Funded status at end of year	$ (19.6)	$ (13.9)