FAIR VALUE MEASUREMENTS - Recurring Assets and Liabilities (Details) - USD ($) $ in Millions	Jun. 30, 2023	Dec. 31, 2022
Liabilities
Restricted cash	$ 43	$ 46
Recurring
Assets
Fair value, assets	536	525
Liabilities
Fair value, liabilities	(5)	(2)
Net assets	531	523
Recurring \| FTRs \| Derivative Liabilities
Liabilities
Fair value, liabilities	(5)	(2)
Recurring \| FTRs \| Derivative Assets
Assets
Fair value, assets	10	11
Recurring \| Equity securities
Assets
Fair value, assets	2	2
Recurring \| U.S. state debt securities
Assets
Fair value, assets	269	266
Recurring \| Cash, cash equivalents and restricted cash
Assets
Fair value, assets	214	206
Recurring \| Other
Assets
Fair value, assets	41	40
Recurring \| Level 1
Assets
Fair value, assets	216	208
Liabilities
Fair value, liabilities	0	0
Net assets	216	208
Recurring \| Level 1 \| FTRs \| Derivative Liabilities
Liabilities
Fair value, liabilities	0	0
Recurring \| Level 1 \| FTRs \| Derivative Assets
Assets
Fair value, assets	0	0
Recurring \| Level 1 \| Equity securities
Assets
Fair value, assets	2	2
Recurring \| Level 1 \| U.S. state debt securities
Assets
Fair value, assets	0	0
Recurring \| Level 1 \| Cash, cash equivalents and restricted cash
Assets
Fair value, assets	214	206
Recurring \| Level 1 \| Other
Assets
Fair value, assets	0	0
Recurring \| Level 2
Assets
Fair value, assets	310	306
Liabilities
Fair value, liabilities	0	0
Net assets	310	306
Recurring \| Level 2 \| FTRs \| Derivative Liabilities
Liabilities
Fair value, liabilities	0	0
Recurring \| Level 2 \| FTRs \| Derivative Assets
Assets
Fair value, assets	0	0
Recurring \| Level 2 \| Equity securities
Assets
Fair value, assets	0	0
Recurring \| Level 2 \| U.S. state debt securities
Assets
Fair value, assets	269	266
Recurring \| Level 2 \| Cash, cash equivalents and restricted cash
Assets
Fair value, assets	0	0
Recurring \| Level 2 \| Other
Assets
Fair value, assets	41	40
Recurring \| Level 3
Assets
Fair value, assets	10	11
Liabilities
Fair value, liabilities	(5)	(2)
Net assets	5	9
Recurring \| Level 3 \| FTRs \| Derivative Liabilities
Liabilities
Fair value, liabilities	(5)	(2)
Recurring \| Level 3 \| FTRs \| Derivative Assets
Assets
Fair value, assets	10	11
Recurring \| Level 3 \| Equity securities
Assets
Fair value, assets	0	0
Recurring \| Level 3 \| U.S. state debt securities
Assets
Fair value, assets	0	0
Recurring \| Level 3 \| Cash, cash equivalents and restricted cash
Assets
Fair value, assets	0	0
Recurring \| Level 3 \| Other
Assets
Fair value, assets	$ 0	$ 0

Fair value of assets and liabilities net.

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- Definition

Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482106/820-10-50-2

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- References

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- Definition

Fair value of financial and nonfinancial obligations.

+ References

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- References

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- Definition

Amount of cash restricted as to withdrawal or usage, classified as current. Cash includes, but is not limited to, currency on hand, demand deposits with banks or financial institutions, and other accounts with general characteristics of demand deposits.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 210
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(1))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480566/210-10-S99-1

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 230
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 8
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482913/230-10-50-8

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