INVESTMENTS - Trading Securities (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Investments, Debt and Equity Securities [Abstract]
Net investment gains (losses) recognized during the period on securities held at the end of the period	$ 422	$ (174)	$ 63
Net investment gains (losses) recognized on securities sold during the period	7	(24)	(19)
Unrealized and realized gains (losses) on trading securities	429	(198)	44
Interest and dividend income from trading securities	283	326	214
Net investment income (loss) from trading securities	$ 712	$ 128	$ 258