BENEFIT PLANS (Components of Net Periodic Benefit Cost- Other Postretirement Benefits) (Details) - Other Postretirement Benefit Plans, Defined Benefit [Member] - USD ($) $ in Millions	3 Months Ended	9 Months Ended	12 Months Ended
	Dec. 31, 2021	Sep. 30, 2021	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Components of Net Periodic Benefit Cost
Service cost			$ 1.3	$ 1.5	$ 1.3
Service cost			1.2
Interest cost			0.5	1.0	1.4
Amortization of prior service credit			(1.5)	(3.9)	(3.9)
Amortization of actuarial gain			(1.4)	(0.8)	(1.3)
Net periodic pension benefit cost (credit)			(1.2)	(2.2)	(2.5)
Changes in Plan Assets and Benefit Obligations Recognized in Other Comprehensive Income
Net actuarial loss (gain)			0.9	(5.1)	2.7
Prior service cost			14.9	0.0	0.0
Reclassification of prior service credit			1.5	3.9	3.9
Reclassification of actuarial gain			1.4	0.8	1.3
Amount recognized in other comprehensive income			18.7	(0.4)	7.9
Amount recognized in net periodic pension benefit cost and other comprehensive income			$ 17.5	$ (2.6)	$ 5.4
Defined Benefit Plan, Assumed Health Care Cost Trend Rates [Abstract]
Rate to which the cost trend rate gradually declines	4.50%		4.50%
Year that the rate reaches the rate it is assumed to maintain			2028
Weighted-average assumptions used to determine net periodic benefit cost for years ended December 31
Discount rate — PBO			2.19%	2.84%	4.01%
Discount rate — service cost	2.84%	2.45%		3.09%	4.23%
Discount rate — interest cost			1.60%	2.42%	3.63%
Weighted-average assumptions used to determine benefit obligation at December 31
Discount rate	2.59%		2.59%	2.09%	2.84%
Pre-65 [Member]
Defined Benefit Plan, Assumed Health Care Cost Trend Rates [Abstract]
Healthcare cost trend rate assumed for next year	6.60%		6.60%
Post-65 [Member]
Defined Benefit Plan, Assumed Health Care Cost Trend Rates [Abstract]
Healthcare cost trend rate assumed for next year	6.50%		6.50%