SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Reclassifications Out of Accumulated Other Comprehensive Income) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2026	Mar. 31, 2025
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	$ 32,792	$ 30,401
Unrealized gain (loss) on investments	(6)	7
Net current period other comprehensive gain (loss)	(6)	7
Ending balance	33,502	30,937
Pension Benefits
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Unrealized gain (loss) on investments	0	0
Amount attributable to tax, before reclassification	0	0
Net current period other comprehensive gain (loss)	0	0
Other Benefits
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Unrealized gain (loss) on investments	0	0
Amount attributable to tax, before reclassification	0	0
Net current period other comprehensive gain (loss)	0	0
Available-for-Sale Securities
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Unrealized gain (loss) on investments	(6)	7
Amount attributable to tax, before reclassification	3	2
Net current period other comprehensive gain (loss)	(6)	7
Accumulated Other Comprehensive Income (Loss)
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	(20)	(14)
Ending balance	(26)	(7)
Accumulated Other Comprehensive Income (Loss) | Pension Benefits
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	(47)	(35)
Ending balance	(47)	(35)
Accumulated Other Comprehensive Income (Loss) | Other Benefits
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	19	18
Ending balance	19	18
Accumulated Other Comprehensive Income (Loss) | Available-for-Sale Securities
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	8	3
Ending balance	2	10
Amortization of net actuarial loss (gain)
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Amounts reclassified from other comprehensive income	(2)	(4)
Amortization of net actuarial loss (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 loss (gain) | Other Benefits
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Amounts reclassified from other comprehensive income	(2)	(4)
Amount attributable to tax, reclassification	1	1
Amortization of net actuarial loss (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	2	4
Regulatory account transfer | 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
Regulatory account transfer | Other Benefits
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Amounts reclassified from other comprehensive income	2	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