SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Reclassifications Out of Accumulated Other 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	$ 30,401	$ 25,292
Unrealized gain on investments	7	(1)
Net current period other comprehensive loss	7	(1)
Ending balance	30,937	25,983
Pension Benefits
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Unrealized gain on investments	0	0
Amount attributable to tax, before reclassification	0	0
Net current period other comprehensive loss	0	0
Other Benefits
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Unrealized gain on investments	0	0
Amount attributable to tax, before reclassification	0	0
Net current period other comprehensive loss	0	0
Available for Sale Securities
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Unrealized gain on investments	7	(1)
Amount attributable to tax, before reclassification	2	1
Net current period other comprehensive loss	7	(1)
Accumulated Other Comprehensive Income (Loss)
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	(14)	(8)
Ending balance	(7)	(9)
Accumulated Other Comprehensive Income (Loss) | Pension Benefits
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	(35)	(28)
Ending balance	(35)	(28)
Accumulated Other Comprehensive Income (Loss) | Other Benefits
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	18	18
Ending balance	18	18
Accumulated Other Comprehensive Income (Loss) | Available for Sale Securities
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	3	2
Ending balance	10	1
Amortization of prior service cost
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Amounts reclassified from other comprehensive income		(1)
Amortization of prior service cost | Pension Benefits
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Amounts reclassified from other comprehensive income		(1)
Amount attributable to tax, reclassification		0
Amortization of prior service cost | Other Benefits
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Amounts reclassified from other comprehensive income		0
Amount attributable to tax, reclassification		0
Amortization of prior service cost | Available for Sale Securities
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Amounts reclassified from other comprehensive income		0
Amount attributable to tax, reclassification		0
Amortization of net actuarial gain
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Amounts reclassified from other comprehensive income	(4)	(4)
Amortization of net actuarial gain | Pension Benefits
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Amounts reclassified from other comprehensive income	0	0
Amount attributable to tax, reclassification	0	0
Amortization of net actuarial gain | Other Benefits
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Amounts reclassified from other comprehensive income	(4)	(4)
Amount attributable to tax, reclassification	1	1
Amortization of net actuarial gain | Available for Sale Securities
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Amounts reclassified from other comprehensive income	0	0
Amount attributable to tax, reclassification	0	0
Regulatory account transfer
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Amounts reclassified from other comprehensive income	4	5
Regulatory account transfer | Pension Benefits
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Amounts reclassified from other comprehensive income	0	1
Amount attributable to tax, reclassification	0	0
Regulatory account transfer | Other Benefits
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Amounts reclassified from other comprehensive income	4	4
Amount attributable to tax, reclassification	1	1
Regulatory account transfer | Available for Sale Securities
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Amounts reclassified from other comprehensive income	0	0
Amount attributable to tax, reclassification	$ 0	$ 0