INVESTMENTS - Debt Securities in HTM in Unrecognized Loss Position (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Fair value
Less than 12 months	$ 17,814	$ 9,716
12 months or longer	19,328	7,322
Total	37,142	17,038
Gross unrecognized losses
Less than 12 months	190	76
12 months or longer	663	194
Total	853	270
Unrealized loss, other than temporary impairment, not credit loss, recorded in AOCI	(653)	(117)
Mortgage-backed securities
Fair value
Less than 12 months	2,822	8,569
12 months or longer	18,086	6,353
Total	20,908	14,922
Gross unrecognized losses
Less than 12 months	20	50
12 months or longer	559	107
Total	579	157
State and municipal securities
Fair value
Less than 12 months	981	353
12 months or longer	1,242	835
Total	2,223	1,188
Gross unrecognized losses
Less than 12 months	34	5
12 months or longer	104	68
Total	138	73
Foreign government
Fair value
Less than 12 months	1,003	723
12 months or longer	0	0
Total	1,003	723
Gross unrecognized losses
Less than 12 months	24	18
12 months or longer	0	0
Total	24	18
Asset-backed securities
Fair value
Less than 12 months	13,008	71
12 months or longer	0	134
Total	13,008	205
Gross unrecognized losses
Less than 12 months	112	3
12 months or longer	0	19
Total	$ 112	$ 22