INVESTMENTS - Debt Securities Held-to-Maturity (Details) - USD ($) $ in Millions	1 Months Ended
	Nov. 30, 2018	Dec. 31, 2018	Dec. 31, 2017
Debt Securities Held-to-maturity
Carrying value		$ 63,357	$ 53,320
Gross unrecognized gains		386	702
Gross unrecognized losses		853	270
Fair value		62,890	53,752
Mortgage-backed securities - U.S. agency-sponsored
Debt Securities Held-to-maturity
Carrying value		34,239	23,880
Gross unrecognized gains		199	40
Gross unrecognized losses		578	157
Fair value		33,860	23,763
Mortgage-backed securities - Alt-A
Debt Securities Held-to-maturity
Carrying value		0	141
Gross unrecognized gains		0	57
Gross unrecognized losses		0	0
Fair value		0	198
Mortgage-backed securities - Non-U.S. residential
Debt Securities Held-to-maturity
Carrying value		1,339	1,841
Gross unrecognized gains		12	65
Gross unrecognized losses		1	0
Fair value		1,350	1,906
Mortgage-backed securities - Commercial
Debt Securities Held-to-maturity
Carrying value		368	237
Gross unrecognized gains		0	0
Gross unrecognized losses		0	0
Fair value		368	237
Mortgage-backed securities
Debt Securities Held-to-maturity
Carrying value		35,946	26,099
Gross unrecognized gains		211	162
Gross unrecognized losses		579	157
Fair value		35,578	26,104
Fair value of securities transferred from AFS to HTM	$ 10,000
Unrealized loss position of securities at time of transfer	$ 598
State and municipal securities
Debt Securities Held-to-maturity
Carrying value		7,628	8,897
Gross unrecognized gains		167	378
Gross unrecognized losses		138	73
Fair value		7,657	9,202
Foreign government
Debt Securities Held-to-maturity
Carrying value		1,027	740
Gross unrecognized gains		0	0
Gross unrecognized losses		24	18
Fair value		1,003	722
Asset-backed securities
Debt Securities Held-to-maturity
Carrying value		18,756	17,584
Gross unrecognized gains		8	162
Gross unrecognized losses		112	22
Fair value		$ 18,652	$ 17,724