QUARTERLY FINANCIAL INFORMATION (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Quarterly Financial Information Disclosure [Abstract]
Total revenues	$ 16,295	$ 16,241	$ 16,245	$ 16,107	$ 14,168	$ 14,206	$ 14,259	$ 14,279	$ 64,888	$ 56,912	$ 53,767
Income (loss) before income taxes	593	888	1,229	746	436	901	19	707	3,456	2,063	4,020
Net income	$ 512	$ 689	$ 940	$ 566	$ 355	$ 644	$ 193	$ 491	$ 2,707	$ 1,683	$ 2,448
Basic earnings per common share (in USD per share)	$ 3.87	$ 5.16	$ 6.96	$ 4.18	$ 2.60	$ 4.68	$ 1.40	$ 3.56	$ 20.20	$ 12.24	$ 16.94
Diluted earnings per common share (in USD per share)	$ 3.84	$ 5.14	$ 6.94	$ 4.16	$ 2.58	$ 4.65	$ 1.39	$ 3.53	$ 20.10	$ 12.16	$ 16.81