INVESTMENTS - Trading Securities (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Debt Securities, Trading, Gain (Loss) [Abstract]
Net investment gains (losses) recognized during the period on securities held at the end of the period	$ 150	$ (99)	$ 424	$ (195)
Net investment gains (losses) recognized on securities sold during the period	1	3	(23)	2
Unrealized and realized gains (losses) on trading securities arising during the period	151	(96)	401	(193)
Interest and dividend income from trading securities	71	73	161	139
Net investment income (loss) from trading securities	$ 222	$ (23)	$ 562	$ (54)