FAIR VALUE MEASUREMENTS - Fair Value Measurement Inputs and Valuation Techniques (Details) $ in Millions		Sep. 30, 2025 USD ($)	Dec. 31, 2024 USD ($)
Fair Value Measurement Inputs and Valuation Techniques
Fixed maturity securities, available-for-sale		$ 67,276	$ 65,269
Equity securities		885	796
Total assets		77,382	74,133
Level 3
Fair Value Measurement Inputs and Valuation Techniques
Fixed maturity securities, available-for-sale		3,246	2,067
Equity securities		163	157
Total assets		3,409	2,224
Adjusted cost valuation technique | Level 3 | Private Financials
Fair Value Measurement Inputs and Valuation Techniques
Equity securities		163	157
Municipalities
Fair Value Measurement Inputs and Valuation Techniques
Fixed maturity securities, available-for-sale		1,986	2,034
Municipalities | Level 3
Fair Value Measurement Inputs and Valuation Techniques
Fixed maturity securities, available-for-sale		0	0
Mortgage- and asset-backed securities
Fair Value Measurement Inputs and Valuation Techniques
Fixed maturity securities, available-for-sale		4,362	3,563
Mortgage- and asset-backed securities | Level 3
Fair Value Measurement Inputs and Valuation Techniques
Fixed maturity securities, available-for-sale		2,246	1,156
Mortgage- and asset-backed securities | Consensus pricing valuation technique | Level 3 | Offered Quotes
Fair Value Measurement Inputs and Valuation Techniques
Fixed maturity securities, available-for-sale		$ 2,246	$ 1,156
Mortgage- and asset-backed securities | Consensus pricing valuation technique | Level 3 | Lower Limit | Offered Quotes
Fair Value Measurement Inputs and Valuation Techniques
Fixed maturity securities, available-for-sale, measurement input	[1]	89.64	84.08
Mortgage- and asset-backed securities | Consensus pricing valuation technique | Level 3 | Upper Limit | Offered Quotes
Fair Value Measurement Inputs and Valuation Techniques
Fixed maturity securities, available-for-sale, measurement input	[1]	106.78	104.60
Mortgage- and asset-backed securities | Consensus pricing valuation technique | Level 3 | Weighted Average | Offered Quotes
Fair Value Measurement Inputs and Valuation Techniques
Fixed maturity securities, available-for-sale, measurement input	[1]	100.52	99.07
Public utilities
Fair Value Measurement Inputs and Valuation Techniques
Fixed maturity securities, available-for-sale		$ 7,430	$ 7,045
Public utilities | Level 3
Fair Value Measurement Inputs and Valuation Techniques
Fixed maturity securities, available-for-sale		806	647
Public utilities | Discounted cash flow technique | Level 3 | Credit Spreads
Fair Value Measurement Inputs and Valuation Techniques
Fixed maturity securities, available-for-sale		$ 806	$ 647
Public utilities | Discounted cash flow technique | Level 3 | Lower Limit | Credit Spreads
Fair Value Measurement Inputs and Valuation Techniques
Fixed maturity securities, available-for-sale, measurement input	[2]	0.0100	0.0100
Public utilities | Discounted cash flow technique | Level 3 | Upper Limit | Credit Spreads
Fair Value Measurement Inputs and Valuation Techniques
Fixed maturity securities, available-for-sale, measurement input	[2]	0.0394	0.0375
Public utilities | Discounted cash flow technique | Level 3 | Weighted Average | Credit Spreads
Fair Value Measurement Inputs and Valuation Techniques
Fixed maturity securities, available-for-sale, measurement input	[2]	0.0166	0.0162
Sovereign and supranational
Fair Value Measurement Inputs and Valuation Techniques
Fixed maturity securities, available-for-sale		$ 425	$ 416
Sovereign and supranational | Level 3
Fair Value Measurement Inputs and Valuation Techniques
Fixed maturity securities, available-for-sale		22	23
Sovereign and supranational | Consensus pricing valuation technique | Level 3 | Offered Quotes
Fair Value Measurement Inputs and Valuation Techniques
Fixed maturity securities, available-for-sale		22	23
Banks/financial institutions
Fair Value Measurement Inputs and Valuation Techniques
Fixed maturity securities, available-for-sale		9,719	8,956
Banks/financial institutions | Level 3
Fair Value Measurement Inputs and Valuation Techniques
Fixed maturity securities, available-for-sale		9	10
Banks/financial institutions | Adjusted cost valuation technique | Level 3 | Private Financials
Fair Value Measurement Inputs and Valuation Techniques
Fixed maturity securities, available-for-sale		9	10
Other corporate
Fair Value Measurement Inputs and Valuation Techniques
Fixed maturity securities, available-for-sale		26,771	25,409
Other corporate | Level 3
Fair Value Measurement Inputs and Valuation Techniques
Fixed maturity securities, available-for-sale		163	231
Other corporate | Discounted cash flow technique | Level 3 | Credit Spreads
Fair Value Measurement Inputs and Valuation Techniques
Fixed maturity securities, available-for-sale		$ 163	$ 231
Other corporate | Discounted cash flow technique | Level 3 | Lower Limit | Credit Spreads
Fair Value Measurement Inputs and Valuation Techniques
Fixed maturity securities, available-for-sale, measurement input	[2]	0.0075	0.0091
Other corporate | Discounted cash flow technique | Level 3 | Upper Limit | Credit Spreads
Fair Value Measurement Inputs and Valuation Techniques
Fixed maturity securities, available-for-sale, measurement input	[2]	0.0384	0.0294
Other corporate | Discounted cash flow technique | Level 3 | Weighted Average | Credit Spreads
Fair Value Measurement Inputs and Valuation Techniques
Fixed maturity securities, available-for-sale, measurement input	[2]	0.0217	0.0173

[1] Represents prices for securities where the Company receives unadjusted broker quotes and for which there is no transparency into the providers' valuation techniques

[2] Actual or equivalent credit spreads in basis points