FAIR VALUE MEASUREMENTS - Fair Value Hierarchy Levels of Assets by Pricing Source, Available-for-sale Securities (Details) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available-for-sale Securities	$ 67,794	$ 68,270
Level 1
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available-for-sale Securities	19,158	18,702
Level 2
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available-for-sale Securities	48,387	49,167
Level 3
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available-for-sale Securities	249	401
Fixed maturities
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available-for-sale Securities	65,349	65,573
Fixed maturities | Level 1
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available-for-sale Securities	18,669	18,683
Fixed maturities | Level 2
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available-for-sale Securities	46,434	46,641
Fixed maturities | Level 3
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available-for-sale Securities	246	249
Perpetual securities
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available-for-sale Securities	1,947	2,669
Perpetual securities | Level 1
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available-for-sale Securities	0	0
Perpetual securities | Level 2
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available-for-sale Securities	1,947	2,520
Perpetual securities | Level 3
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available-for-sale Securities	0	149
Equity securities
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available-for-sale Securities	498	28
Equity securities | Level 1
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available-for-sale Securities	489	19
Equity securities | Level 2
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available-for-sale Securities	6	6
Equity securities | Level 3
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available-for-sale Securities	3	3
Equity securities | Third party pricing vendor valuation technique
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available-for-sale Securities	495	25
Equity securities | Third party pricing vendor valuation technique | Level 1
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available-for-sale Securities	489	19
Equity securities | Third party pricing vendor valuation technique | Level 2
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available-for-sale Securities	6	6
Equity securities | Third party pricing vendor valuation technique | Level 3
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available-for-sale Securities	0	0
Equity securities | Net asset value valuation technique
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available-for-sale Securities	3	3
Equity securities | Net asset value valuation technique | Level 1
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available-for-sale Securities	0	0
Equity securities | Net asset value valuation technique | Level 2
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available-for-sale Securities	0	0
Equity securities | Net asset value valuation technique | Level 3
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available-for-sale Securities	3	3
Government and agencies | Fixed maturities
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available-for-sale Securities	19,276	19,198
Government and agencies | Fixed maturities | Level 1
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available-for-sale Securities	18,669	18,683
Government and agencies | Fixed maturities | Level 2
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available-for-sale Securities	607	515
Government and agencies | Fixed maturities | Level 3
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available-for-sale Securities	0	0
Government and agencies | Fixed maturities | Third party pricing vendor valuation technique
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available-for-sale Securities	19,276	19,198
Government and agencies | Fixed maturities | Third party pricing vendor valuation technique | Level 1
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available-for-sale Securities	18,669	18,683
Government and agencies | Fixed maturities | Third party pricing vendor valuation technique | Level 2
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available-for-sale Securities	607	515
Government and agencies | Fixed maturities | Third party pricing vendor valuation technique | Level 3
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available-for-sale Securities	0	0
Municipalities | Fixed maturities
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available-for-sale Securities	1,208	1,257
Municipalities | Fixed maturities | Level 1
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available-for-sale Securities	0	0
Municipalities | Fixed maturities | Level 2
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available-for-sale Securities	1,208	1,257
Municipalities | Fixed maturities | Level 3
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available-for-sale Securities	0	0
Municipalities | Fixed maturities | Third party pricing vendor valuation technique
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available-for-sale Securities	1,208	1,257
Municipalities | Fixed maturities | Third party pricing vendor valuation technique | Level 1
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available-for-sale Securities	0	0
Municipalities | Fixed maturities | Third party pricing vendor valuation technique | Level 2
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available-for-sale Securities	1,208	1,257
Municipalities | Fixed maturities | Third party pricing vendor valuation technique | Level 3
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available-for-sale Securities	0	0
Mortgage- and asset-backed securities | Fixed maturities
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available-for-sale Securities	582	602
Mortgage- and asset-backed securities | Fixed maturities | Level 1
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available-for-sale Securities	0	0
Mortgage- and asset-backed securities | Fixed maturities | Level 2
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available-for-sale Securities	362	379
Mortgage- and asset-backed securities | Fixed maturities | Level 3
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available-for-sale Securities	220	223
Mortgage- and asset-backed securities | Fixed maturities | Third party pricing vendor valuation technique
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available-for-sale Securities	362	379
Mortgage- and asset-backed securities | Fixed maturities | Third party pricing vendor valuation technique | Level 1
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available-for-sale Securities	0	0
Mortgage- and asset-backed securities | Fixed maturities | Third party pricing vendor valuation technique | Level 2
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available-for-sale Securities	362	379
Mortgage- and asset-backed securities | Fixed maturities | Third party pricing vendor valuation technique | Level 3
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available-for-sale Securities	0	0
Mortgage- and asset-backed securities | Fixed maturities | Consensus pricing valuation technique
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available-for-sale Securities	220	223
Mortgage- and asset-backed securities | Fixed maturities | Consensus pricing valuation technique | Level 1
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available-for-sale Securities	0	0
Mortgage- and asset-backed securities | Fixed maturities | Consensus pricing valuation technique | Level 2
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available-for-sale Securities	0	0
Mortgage- and asset-backed securities | Fixed maturities | Consensus pricing valuation technique | Level 3
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available-for-sale Securities	220	223
Public utilities | Fixed maturities
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available-for-sale Securities	7,479	7,897
Public utilities | Fixed maturities | Level 1
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available-for-sale Securities	0	0
Public utilities | Fixed maturities | Level 2
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available-for-sale Securities	7,479	7,897
Public utilities | Fixed maturities | Level 3
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available-for-sale Securities	0	0
Public utilities | Fixed maturities | Third party pricing vendor valuation technique
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available-for-sale Securities	7,479	7,897
Public utilities | Fixed maturities | Third party pricing vendor valuation technique | Level 1
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available-for-sale Securities	0	0
Public utilities | Fixed maturities | Third party pricing vendor valuation technique | Level 2
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available-for-sale Securities	7,479	7,897
Public utilities | Fixed maturities | Third party pricing vendor valuation technique | Level 3
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available-for-sale Securities	0	0
Sovereign and supranational | Fixed maturities
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available-for-sale Securities	1,407	1,416
Sovereign and supranational | Fixed maturities | Level 1
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available-for-sale Securities	0	0
Sovereign and supranational | Fixed maturities | Level 2
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available-for-sale Securities	1,407	1,416
Sovereign and supranational | Fixed maturities | Level 3
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available-for-sale Securities	0	0
Sovereign and supranational | Fixed maturities | Third party pricing vendor valuation technique
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available-for-sale Securities	1,407	1,416
Sovereign and supranational | Fixed maturities | Third party pricing vendor valuation technique | Level 1
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available-for-sale Securities	0	0
Sovereign and supranational | Fixed maturities | Third party pricing vendor valuation technique | Level 2
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available-for-sale Securities	1,407	1,416
Sovereign and supranational | Fixed maturities | Third party pricing vendor valuation technique | Level 3
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available-for-sale Securities	0	0
Banks/financial institutions | Fixed maturities
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available-for-sale Securities	6,019	6,598
Banks/financial institutions | Fixed maturities | Level 1
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available-for-sale Securities	0	0
Banks/financial institutions | Fixed maturities | Level 2
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available-for-sale Securities	5,993	6,572
Banks/financial institutions | Fixed maturities | Level 3
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available-for-sale Securities	26	26
Banks/financial institutions | Fixed maturities | Third party pricing vendor valuation technique
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available-for-sale Securities	5,993	6,514
Banks/financial institutions | Fixed maturities | Third party pricing vendor valuation technique | Level 1
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available-for-sale Securities	0	0
Banks/financial institutions | Fixed maturities | Third party pricing vendor valuation technique | Level 2
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available-for-sale Securities	5,993	6,514
Banks/financial institutions | Fixed maturities | Third party pricing vendor valuation technique | Level 3
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available-for-sale Securities	0	0
Banks/financial institutions | Fixed maturities | Consensus pricing valuation technique
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available-for-sale Securities	26	84
Banks/financial institutions | Fixed maturities | Consensus pricing valuation technique | Level 1
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available-for-sale Securities	0	0
Banks/financial institutions | Fixed maturities | Consensus pricing valuation technique | Level 2
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available-for-sale Securities	0	58
Banks/financial institutions | Fixed maturities | Consensus pricing valuation technique | Level 3
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available-for-sale Securities	26	26
Banks/financial institutions | Perpetual securities
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available-for-sale Securities	1,742	2,438
Banks/financial institutions | Perpetual securities | Level 1
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available-for-sale Securities	0	0
Banks/financial institutions | Perpetual securities | Level 2
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available-for-sale Securities	1,742	2,289
Banks/financial institutions | Perpetual securities | Level 3
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available-for-sale Securities	0	149
Banks/financial institutions | Perpetual securities | Third party pricing vendor valuation technique
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available-for-sale Securities	1,742	2,289
Banks/financial institutions | Perpetual securities | Third party pricing vendor valuation technique | Level 1
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available-for-sale Securities	0	0
Banks/financial institutions | Perpetual securities | Third party pricing vendor valuation technique | Level 2
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available-for-sale Securities	1,742	2,289
Banks/financial institutions | Perpetual securities | Third party pricing vendor valuation technique | Level 3
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available-for-sale Securities	0	0
Banks/financial institutions | Perpetual securities | Consensus pricing valuation technique
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available-for-sale Securities		149
Banks/financial institutions | Perpetual securities | Consensus pricing valuation technique | Level 1
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available-for-sale Securities		0
Banks/financial institutions | Perpetual securities | Consensus pricing valuation technique | Level 2
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available-for-sale Securities		0
Banks/financial institutions | Perpetual securities | Consensus pricing valuation technique | Level 3
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available-for-sale Securities		149
Other corporate | Fixed maturities
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available-for-sale Securities	29,378	28,605
Other corporate | Fixed maturities | Level 1
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available-for-sale Securities	0	0
Other corporate | Fixed maturities | Level 2
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available-for-sale Securities	29,378	28,605
Other corporate | Fixed maturities | Level 3
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available-for-sale Securities	0	0
Other corporate | Fixed maturities | Third party pricing vendor valuation technique
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available-for-sale Securities	29,378	28,605
Other corporate | Fixed maturities | Third party pricing vendor valuation technique | Level 1
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available-for-sale Securities	0	0
Other corporate | Fixed maturities | Third party pricing vendor valuation technique | Level 2
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available-for-sale Securities	29,378	28,605
Other corporate | Fixed maturities | Third party pricing vendor valuation technique | Level 3
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available-for-sale Securities	0	0
Other corporate | Perpetual securities
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available-for-sale Securities	205	231
Other corporate | Perpetual securities | Level 1
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available-for-sale Securities	0	0
Other corporate | Perpetual securities | Level 2
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available-for-sale Securities	205	231
Other corporate | Perpetual securities | Level 3
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available-for-sale Securities	0	0
Other corporate | Perpetual securities | Third party pricing vendor valuation technique
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available-for-sale Securities	205	231
Other corporate | Perpetual securities | Third party pricing vendor valuation technique | Level 1
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available-for-sale Securities	0	0
Other corporate | Perpetual securities | Third party pricing vendor valuation technique | Level 2
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available-for-sale Securities	205	231
Other corporate | Perpetual securities | Third party pricing vendor valuation technique | Level 3
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available-for-sale Securities	$ 0	$ 0