INVESTMENTS - Equity Securities (Details) $ in Millions	Dec. 31, 2018 USD ($)
Equity Securities, FV-NI [Line Items]
Fair Value	$ 987	[1],[2],[3]
Yen-denominated
Equity Securities, FV-NI [Line Items]
Fair Value	641
Dollar-denominated
Equity Securities, FV-NI [Line Items]
Fair Value	346
Equity securities
Equity Securities, FV-NI [Line Items]
Perpetual securities, fair value	$ 62

[1] Includes perpetual securities ($62 at fair value)

[2] Includes perpetual securities

[3] Includes perpetual securities