INVESTMENTS - TRADING SECURITIES (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Debt Securities, Trading, Gain (Loss) [Abstract]
Net investment gains (losses) recognized during the period on securities held at the end of the period	$ (108)	$ 57	$ (172)	$ 108
Net investment gains (losses) recognized on securities sold during the period	(10)	23	(9)	25
Unrealized and realized gains (losses) on trading securities arising during the period	(118)	80	(181)	133
Interest and dividend income from trading securities	80	49	146	89
Net investment income (loss) from trading securities	$ (38)	$ 129	$ (35)	$ 222