COMPREHENSIVE INCOME - Schedule of Comprehensive Income (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2025	Mar. 31, 2024
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	$ 26,986.1	$ 25,285.9
TOTAL OTHER COMPREHENSIVE INCOME (LOSS)	23.4	(6.8)
Ending balance	27,364.0	25,843.7
Total
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	(3.1)	(55.5)
Change in Fair Value Recognized in AOCI, Net of Tax	37.2	17.9
Amount of (Gain) Loss Reclassified from AOCI	(17.5)	(31.3)
Income Tax (Expense) Benefit	(3.7)	(6.6)
Reclassifications from AOCI, Net of Income Tax (Expense) Benefit	(13.8)	(24.7)
TOTAL OTHER COMPREHENSIVE INCOME (LOSS)	23.4	(6.8)
Ending balance	20.3	(62.3)
Pension and OPEB
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	(104.9)	(152.3)
Change in Fair Value Recognized in AOCI, Net of Tax	0.0	0.0
Amount of (Gain) Loss Reclassified from AOCI	0.4	(0.8)
Income Tax (Expense) Benefit	0.1	(0.2)
Reclassifications from AOCI, Net of Income Tax (Expense) Benefit	0.3	(0.6)
TOTAL OTHER COMPREHENSIVE INCOME (LOSS)	0.3	(0.6)
Ending balance	(104.6)	(152.9)
Amortization of Prior Service Cost (Credit)
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Amount of (Gain) Loss Reclassified from AOCI	(0.1)	(1.3)
Amortization of Actuarial (Gains) Losses
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Amount of (Gain) Loss Reclassified from AOCI	0.5	0.5
Commodity | Cash Flow Hedges
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	98.5	104.9
Change in Fair Value Recognized in AOCI, Net of Tax	38.2	5.5
Amount of (Gain) Loss Reclassified from AOCI	(16.5)	(29.3)
Income Tax (Expense) Benefit	(3.5)	(6.1)
Reclassifications from AOCI, Net of Income Tax (Expense) Benefit	(13.0)	(23.2)
TOTAL OTHER COMPREHENSIVE INCOME (LOSS)	25.2	(17.7)
Ending balance	123.7	87.2
Interest Rate | Cash Flow Hedges
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	3.3	(8.1)
Change in Fair Value Recognized in AOCI, Net of Tax	(1.0)	12.4
Amount of (Gain) Loss Reclassified from AOCI	(1.4)	(1.2)
Income Tax (Expense) Benefit	(0.3)	(0.3)
Reclassifications from AOCI, Net of Income Tax (Expense) Benefit	(1.1)	(0.9)
TOTAL OTHER COMPREHENSIVE INCOME (LOSS)	(2.1)	11.5
Ending balance	$ 1.2	$ 3.4