FAIR VALUE MEASUREMENTS - Fair Value Hierarchy Levels of Assets by Pricing Source, Securities Carried at Fair Value (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available for sale, fixed maturity securities	$ 91,262	$ 82,895
Equity securities	802	987
Level 1
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available for sale, fixed maturity securities	34,878	32,993
Equity securities	642	874
Level 2
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available for sale, fixed maturity securities	55,697	49,380
Equity securities	80	67
Level 3
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available for sale, fixed maturity securities	687	522
Equity securities	80	46
Third party pricing vendor valuation technique
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Equity securities	722	941
Third party pricing vendor valuation technique | Level 1
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Equity securities	642	874
Third party pricing vendor valuation technique | Level 2
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Equity securities	80	67
Third party pricing vendor valuation technique | Level 3
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Equity securities	0	0
Net asset value valuation technique
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Equity securities	80	46
Net asset value valuation technique | Level 1
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Equity securities	0	0
Net asset value valuation technique | Level 2
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Equity securities	0	0
Net asset value valuation technique | Level 3
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Equity securities	80	46
Government and agencies
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available for sale, fixed maturity securities	36,400	34,342
Government and agencies | Level 1
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available for sale, fixed maturity securities	34,878	32,993
Government and agencies | Level 2
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available for sale, fixed maturity securities	1,522	1,349
Government and agencies | Level 3
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available for sale, fixed maturity securities	0	0
Government and agencies | Third party pricing vendor valuation technique
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available for sale, fixed maturity securities	36,400	34,342
Government and agencies | Third party pricing vendor valuation technique | Level 1
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available for sale, fixed maturity securities	34,878	32,993
Government and agencies | Third party pricing vendor valuation technique | Level 2
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available for sale, fixed maturity securities	1,522	1,349
Government and agencies | Third party pricing vendor valuation technique | Level 3
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available for sale, fixed maturity securities	0	0
Municipalities
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available for sale, fixed maturity securities	1,847	1,863
Municipalities | Level 1
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available for sale, fixed maturity securities	0	0
Municipalities | Level 2
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available for sale, fixed maturity securities	1,847	1,863
Municipalities | Level 3
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available for sale, fixed maturity securities	0	0
Municipalities | Third party pricing vendor valuation technique
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available for sale, fixed maturity securities	1,847	1,863
Municipalities | Third party pricing vendor valuation technique | Level 1
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available for sale, fixed maturity securities	0	0
Municipalities | Third party pricing vendor valuation technique | Level 2
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available for sale, fixed maturity securities	1,847	1,863
Municipalities | Third party pricing vendor valuation technique | Level 3
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available for sale, fixed maturity securities	0	0
Mortgage- and asset-backed securities
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available for sale, fixed maturity securities	410	339
Mortgage- and asset-backed securities | Level 1
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available for sale, fixed maturity securities	0	0
Mortgage- and asset-backed securities | Level 2
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available for sale, fixed maturity securities	232	162
Mortgage- and asset-backed securities | Level 3
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available for sale, fixed maturity securities	178	177
Mortgage- and asset-backed securities | Third party pricing vendor valuation technique
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available for sale, fixed maturity securities	232	162
Mortgage- and asset-backed securities | Third party pricing vendor valuation technique | Level 1
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available for sale, fixed maturity securities	0	0
Mortgage- and asset-backed securities | Third party pricing vendor valuation technique | Level 2
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available for sale, fixed maturity securities	232	162
Mortgage- and asset-backed securities | Third party pricing vendor valuation technique | Level 3
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available for sale, fixed maturity securities	0	0
Mortgage- and asset-backed securities | Consensus pricing valuation technique
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available for sale, fixed maturity securities	178	177
Mortgage- and asset-backed securities | Consensus pricing valuation technique | Level 1
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available for sale, fixed maturity securities	0	0
Mortgage- and asset-backed securities | Consensus pricing valuation technique | Level 2
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available for sale, fixed maturity securities	0	0
Mortgage- and asset-backed securities | Consensus pricing valuation technique | Level 3
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available for sale, fixed maturity securities	178	177
Public utilities
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available for sale, fixed maturity securities	6,780	7,171
Public utilities | Level 1
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available for sale, fixed maturity securities	0	0
Public utilities | Level 2
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available for sale, fixed maturity securities	6,556	7,062
Public utilities | Level 3
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available for sale, fixed maturity securities	224	109
Public utilities | Third party pricing vendor valuation technique
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available for sale, fixed maturity securities	6,556	7,062
Public utilities | Third party pricing vendor valuation technique | Level 1
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available for sale, fixed maturity securities	0	0
Public utilities | Third party pricing vendor valuation technique | Level 2
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available for sale, fixed maturity securities	6,556	7,062
Public utilities | Third party pricing vendor valuation technique | Level 3
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available for sale, fixed maturity securities	0	0
Public utilities | Discounted cash flow technique
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available for sale, fixed maturity securities	224	109
Public utilities | Discounted cash flow technique | Level 1
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available for sale, fixed maturity securities	0	0
Public utilities | Discounted cash flow technique | Level 2
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available for sale, fixed maturity securities	0	0
Public utilities | Discounted cash flow technique | Level 3
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available for sale, fixed maturity securities	224	109
Sovereign and supranational
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available for sale, fixed maturity securities	1,042	1,260
Sovereign and supranational | Level 1
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available for sale, fixed maturity securities	0	0
Sovereign and supranational | Level 2
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available for sale, fixed maturity securities	1,042	1,260
Sovereign and supranational | Level 3
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available for sale, fixed maturity securities	0	0
Sovereign and supranational | Third party pricing vendor valuation technique
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available for sale, fixed maturity securities	1,042	1,260
Sovereign and supranational | Third party pricing vendor valuation technique | Level 1
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available for sale, fixed maturity securities	0	0
Sovereign and supranational | Third party pricing vendor valuation technique | Level 2
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available for sale, fixed maturity securities	1,042	1,260
Sovereign and supranational | Third party pricing vendor valuation technique | Level 3
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available for sale, fixed maturity securities	0	0
Banks/financial institutions
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available for sale, fixed maturity securities	10,287	8,918
Banks/financial institutions | Level 1
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available for sale, fixed maturity securities	0	0
Banks/financial institutions | Level 2
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available for sale, fixed maturity securities	10,264	8,895
Banks/financial institutions | Level 3
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available for sale, fixed maturity securities	23	23
Banks/financial institutions | Third party pricing vendor valuation technique
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available for sale, fixed maturity securities	10,264	8,895
Banks/financial institutions | Third party pricing vendor valuation technique | Level 1
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available for sale, fixed maturity securities	0	0
Banks/financial institutions | Third party pricing vendor valuation technique | Level 2
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available for sale, fixed maturity securities	10,264	8,895
Banks/financial institutions | Third party pricing vendor valuation technique | Level 3
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available for sale, fixed maturity securities	0	0
Banks/financial institutions | Consensus pricing valuation technique
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available for sale, fixed maturity securities	23	23
Banks/financial institutions | Consensus pricing valuation technique | Level 1
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available for sale, fixed maturity securities	0	0
Banks/financial institutions | Consensus pricing valuation technique | Level 2
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available for sale, fixed maturity securities	0	0
Banks/financial institutions | Consensus pricing valuation technique | Level 3
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available for sale, fixed maturity securities	23	23
Other corporate
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available for sale, fixed maturity securities	34,496	29,002
Other corporate | Level 1
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available for sale, fixed maturity securities	0	0
Other corporate | Level 2
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available for sale, fixed maturity securities	34,234	28,789
Other corporate | Level 3
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available for sale, fixed maturity securities	262	213
Other corporate | Third party pricing vendor valuation technique
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available for sale, fixed maturity securities	34,234	28,789
Other corporate | Third party pricing vendor valuation technique | Level 1
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available for sale, fixed maturity securities	0	0
Other corporate | Third party pricing vendor valuation technique | Level 2
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available for sale, fixed maturity securities	34,234	28,789
Other corporate | Third party pricing vendor valuation technique | Level 3
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available for sale, fixed maturity securities	0	0
Other corporate | Discounted cash flow technique
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available for sale, fixed maturity securities	262	213
Other corporate | Discounted cash flow technique | Level 1
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available for sale, fixed maturity securities	0	0
Other corporate | Discounted cash flow technique | Level 2
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available for sale, fixed maturity securities	0	0
Other corporate | Discounted cash flow technique | Level 3
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available for sale, fixed maturity securities	$ 262	$ 213