Face (par) amount of debt instrument at time of issuance.

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Name:	us-gaap_DebtInstrumentFaceAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

FAIR VALUE MEASUREMENTS - Narrative (Details) - USD ($)	3 Months Ended
FAIR VALUE MEASUREMENTS - Narrative (Details) - USD ($)	Mar. 31, 2023	Mar. 31, 2022	Apr. 20, 2023	Dec. 31, 2022
Fair Value of Financial Instruments [Line Items]
Investments not required to be disclosed	$ 356,000,000			$ 351,000,000
Unsecured Notes at 5.13% Due 2033 \| Unsecured Debt \| ATSI \| Subsequent Event
Fair Value of Financial Instruments [Line Items]
Face amount of debt			$ 150,000,000
Issuance interest rate			5.13%
Corporate-Owned Life Insurance
Fair Value of Financial Instruments [Line Items]
Gain (loss) on investments	$ 7,000,000	$ (6,000,000)