INVESTMENTS - Trading Securities (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Investments, Debt and Equity Securities [Abstract]
Net investment gains (losses) recognized during the period on securities held at the end of the period	$ 96	$ 422	$ (174)
Net investment gains (losses) recognized on securities sold during the period	10	7	(24)
Unrealized and realized gains (losses) on trading securities	106	429	(198)
Interest and dividend income from trading securities	206	283	326
Net investment income (loss) from trading securities	$ 312	$ 712	$ 128