FAIR VALUE MEASUREMENTS - Fair Value Hierarchy Levels of Assets by Pricing Source, Held-to-Maturity Securities (Details) - USD ($) $ in Millions	Mar. 31, 2016	Dec. 31, 2015
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities held to maturity, fixed maturities, fair value	$ 42,807	$ 37,520
Fixed maturities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities held to maturity, fixed maturities, fair value	42,807	37,520
Fixed maturities | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities held to maturity, fixed maturities, fair value	27,595	23,391
Fixed maturities | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities held to maturity, fixed maturities, fair value	15,185	14,103
Fixed maturities | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities held to maturity, fixed maturities, fair value	27	26
Government and agencies | Fixed maturities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities held to maturity, fixed maturities, fair value	27,595	23,391
Government and agencies | Fixed maturities | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities held to maturity, fixed maturities, fair value	27,595	23,391
Government and agencies | Fixed maturities | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities held to maturity, fixed maturities, fair value	0	0
Government and agencies | Fixed maturities | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities held to maturity, fixed maturities, fair value	0	0
Government and agencies | Fixed maturities | Third party pricing vendor valuation technique
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities held to maturity, fixed maturities, fair value	27,595	23,391
Government and agencies | Fixed maturities | Third party pricing vendor valuation technique | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities held to maturity, fixed maturities, fair value	27,595	23,391
Government and agencies | Fixed maturities | Third party pricing vendor valuation technique | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities held to maturity, fixed maturities, fair value	0	0
Government and agencies | Fixed maturities | Third party pricing vendor valuation technique | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities held to maturity, fixed maturities, fair value	0	0
Municipalities | Fixed maturities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities held to maturity, fixed maturities, fair value	487	415
Municipalities | Fixed maturities | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities held to maturity, fixed maturities, fair value	0	0
Municipalities | Fixed maturities | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities held to maturity, fixed maturities, fair value	487	415
Municipalities | Fixed maturities | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities held to maturity, fixed maturities, fair value	0	0
Municipalities | Fixed maturities | Third party pricing vendor valuation technique
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities held to maturity, fixed maturities, fair value	487	415
Municipalities | Fixed maturities | Third party pricing vendor valuation technique | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities held to maturity, fixed maturities, fair value	0	0
Municipalities | Fixed maturities | Third party pricing vendor valuation technique | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities held to maturity, fixed maturities, fair value	487	415
Municipalities | Fixed maturities | Third party pricing vendor valuation technique | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities held to maturity, fixed maturities, fair value	0	0
Mortgage- and asset-backed securities | Fixed maturities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities held to maturity, fixed maturities, fair value	40	38
Mortgage- and asset-backed securities | Fixed maturities | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities held to maturity, fixed maturities, fair value	0	0
Mortgage- and asset-backed securities | Fixed maturities | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities held to maturity, fixed maturities, fair value	13	12
Mortgage- and asset-backed securities | Fixed maturities | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities held to maturity, fixed maturities, fair value	27	26
Mortgage- and asset-backed securities | Fixed maturities | Third party pricing vendor valuation technique
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities held to maturity, fixed maturities, fair value	13	12
Mortgage- and asset-backed securities | Fixed maturities | Third party pricing vendor valuation technique | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities held to maturity, fixed maturities, fair value	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 and Nonrecurring Basis [Line Items]
Securities held to maturity, fixed maturities, fair value	13	12
Mortgage- and asset-backed securities | Fixed maturities | Third party pricing vendor valuation technique | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities held to maturity, fixed maturities, fair value	0	0
Mortgage- and asset-backed securities | Fixed maturities | Consensus pricing valuation technique
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities held to maturity, fixed maturities, fair value	27	26
Mortgage- and asset-backed securities | Fixed maturities | Consensus pricing valuation technique | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities held to maturity, fixed maturities, fair value	0	0
Mortgage- and asset-backed securities | Fixed maturities | Consensus pricing valuation technique | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities held to maturity, fixed maturities, fair value	0	0
Mortgage- and asset-backed securities | Fixed maturities | Consensus pricing valuation technique | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities held to maturity, fixed maturities, fair value	27	26
Public utilities | Fixed maturities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities held to maturity, fixed maturities, fair value	3,520	3,203
Public utilities | Fixed maturities | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities held to maturity, fixed maturities, fair value	0	0
Public utilities | Fixed maturities | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities held to maturity, fixed maturities, fair value	3,520	3,203
Public utilities | Fixed maturities | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities held to maturity, fixed maturities, fair value	0	0
Public utilities | Fixed maturities | Third party pricing vendor valuation technique
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities held to maturity, fixed maturities, fair value	3,520	3,203
Public utilities | Fixed maturities | Third party pricing vendor valuation technique | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities held to maturity, fixed maturities, fair value	0	0
Public utilities | Fixed maturities | Third party pricing vendor valuation technique | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities held to maturity, fixed maturities, fair value	3,520	3,203
Public utilities | Fixed maturities | Third party pricing vendor valuation technique | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities held to maturity, fixed maturities, fair value	0	0
Sovereign and supranational | Fixed maturities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities held to maturity, fixed maturities, fair value	2,987	2,711
Sovereign and supranational | Fixed maturities | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities held to maturity, fixed maturities, fair value	0	0
Sovereign and supranational | Fixed maturities | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities held to maturity, fixed maturities, fair value	2,987	2,711
Sovereign and supranational | Fixed maturities | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities held to maturity, fixed maturities, fair value	0	0
Sovereign and supranational | Fixed maturities | Third party pricing vendor valuation technique
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities held to maturity, fixed maturities, fair value	2,987	2,711
Sovereign and supranational | Fixed maturities | Third party pricing vendor valuation technique | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities held to maturity, fixed maturities, fair value	0	0
Sovereign and supranational | Fixed maturities | Third party pricing vendor valuation technique | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities held to maturity, fixed maturities, fair value	2,987	2,711
Sovereign and supranational | Fixed maturities | Third party pricing vendor valuation technique | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities held to maturity, fixed maturities, fair value	0	0
Banks/financial institutions | Fixed maturities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities held to maturity, fixed maturities, fair value	4,731	4,546
Banks/financial institutions | Fixed maturities | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities held to maturity, fixed maturities, fair value	0	0
Banks/financial institutions | Fixed maturities | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities held to maturity, fixed maturities, fair value	4,731	4,546
Banks/financial institutions | Fixed maturities | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities held to maturity, fixed maturities, fair value	0	0
Banks/financial institutions | Fixed maturities | Third party pricing vendor valuation technique
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities held to maturity, fixed maturities, fair value	4,731	4,546
Banks/financial institutions | Fixed maturities | Third party pricing vendor valuation technique | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities held to maturity, fixed maturities, fair value	0	0
Banks/financial institutions | Fixed maturities | Third party pricing vendor valuation technique | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities held to maturity, fixed maturities, fair value	4,731	4,546
Banks/financial institutions | Fixed maturities | Third party pricing vendor valuation technique | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities held to maturity, fixed maturities, fair value	0	0
Other corporate | Fixed maturities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities held to maturity, fixed maturities, fair value	3,447	3,216
Other corporate | Fixed maturities | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities held to maturity, fixed maturities, fair value	0	0
Other corporate | Fixed maturities | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities held to maturity, fixed maturities, fair value	3,447	3,216
Other corporate | Fixed maturities | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities held to maturity, fixed maturities, fair value	0	0
Other corporate | Fixed maturities | Third party pricing vendor valuation technique
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities held to maturity, fixed maturities, fair value	3,447	3,189
Other corporate | Fixed maturities | Third party pricing vendor valuation technique | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities held to maturity, fixed maturities, fair value	0	0
Other corporate | Fixed maturities | Third party pricing vendor valuation technique | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities held to maturity, fixed maturities, fair value	3,447	3,189
Other corporate | Fixed maturities | Third party pricing vendor valuation technique | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities held to maturity, fixed maturities, fair value	$ 0	0
Other corporate | Fixed maturities | Consensus pricing valuation technique
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities held to maturity, fixed maturities, fair value		27
Other corporate | Fixed maturities | Consensus pricing valuation technique | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities held to maturity, fixed maturities, fair value		0
Other corporate | Fixed maturities | Consensus pricing valuation technique | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities held to maturity, fixed maturities, fair value		27
Other corporate | Fixed maturities | Consensus pricing valuation technique | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities held to maturity, fixed maturities, fair value		$ 0