INVESTMENTS - Equity Securities (Details) $ in Millions	Jun. 30, 2018 USD ($)
Equity Securities, FV-NI [Line Items]
Fair Value	$ 1,103	[1],[2]
Yen-denominated
Equity Securities, FV-NI [Line Items]
Fair Value	712
Dollar-denominated
Equity Securities, FV-NI [Line Items]
Fair Value	391
Equity securities
Equity Securities, FV-NI [Line Items]
Perpetual securities, fair value	$ 69

[1] Includes perpetual securities

[2] Includes perpetual securities ($69 at fair value)