INVESTMENTS - Securities Lending Transactions Accounted for as Secured Borrowings (Details) - USD ($) $ in Millions		Jun. 30, 2017	Dec. 31, 2016
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities Loaned, Including Not Subject to Master Netting Arrangement and Assets other than Securities Transferred		$ 663	$ 526
Gross amount of recognized liabilities for securities lending		663	526
Amounts related to agreements not included in offsetting disclosure in Note 4		0	0
Public utilities
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities Loaned, Including Not Subject to Master Netting Arrangement and Assets other than Securities Transferred		63	62
Banks/financial institutions
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities Loaned, Including Not Subject to Master Netting Arrangement and Assets other than Securities Transferred		38	34
Other corporate
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities Loaned, Including Not Subject to Master Netting Arrangement and Assets other than Securities Transferred		556	430
Equity securities
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities Loaned, Including Not Subject to Master Netting Arrangement and Assets other than Securities Transferred		6
Maturity Overnight and Continuous
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities Loaned, Including Not Subject to Master Netting Arrangement and Assets other than Securities Transferred	[1]	663	526
Maturity Overnight and Continuous | Public utilities
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities Loaned, Including Not Subject to Master Netting Arrangement and Assets other than Securities Transferred	[1]	63	62
Maturity Overnight and Continuous | Banks/financial institutions
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities Loaned, Including Not Subject to Master Netting Arrangement and Assets other than Securities Transferred	[1]	38	34
Maturity Overnight and Continuous | Other corporate
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities Loaned, Including Not Subject to Master Netting Arrangement and Assets other than Securities Transferred	[1]	556	430
Maturity Overnight and Continuous | Equity securities
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities Loaned, Including Not Subject to Master Netting Arrangement and Assets other than Securities Transferred	[1]	6
Maturity up to 30 Days
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities Loaned, Including Not Subject to Master Netting Arrangement and Assets other than Securities Transferred		0	0
Maturity up to 30 Days | Public utilities
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities Loaned, Including Not Subject to Master Netting Arrangement and Assets other than Securities Transferred		0	0
Maturity up to 30 Days | Banks/financial institutions
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities Loaned, Including Not Subject to Master Netting Arrangement and Assets other than Securities Transferred		0	0
Maturity up to 30 Days | Other corporate
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities Loaned, Including Not Subject to Master Netting Arrangement and Assets other than Securities Transferred		0	$ 0
Maturity up to 30 Days | Equity securities
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities Loaned, Including Not Subject to Master Netting Arrangement and Assets other than Securities Transferred		$ 0

[1] These securities are pledged as collateral under our U.S. securities lending program and can be called at our discretion; therefore, they are classified as Overnight and Continuous.