INVESTMENT SECURITIES - Schedule of Investment Securities (Details) - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020
Debt and Equity Securities, FV-NI [Line Items]
Equity (Baker Hughes)	$ 6,741	$ 7,319
Current investment securities	6,741	7,319
Gross unrealized losses	(168)
Equity securities	239	218
Non-current investment securities, amortized cost	35,152	34,313
Non-current investment securities, gross unrealized gains	5,801	8,342
Non-current investment securities, gross unrealized losses	(168)	(106)
Non-current investment securities, estimated fair value	40,786	42,549
Amortized cost	41,893	41,632
Gross unrealized gains	5,801	8,342
Gross unrealized losses		(106)
Estimated fair value	47,527	49,868
U.S. corporate
Debt and Equity Securities, FV-NI [Line Items]
Amortized cost	24,159	23,604
Gross unrealized gains	4,616	6,651
Gross unrealized losses	(79)	(26)
Estimated fair value	28,695	30,230
Non-U.S. corporate
Debt and Equity Securities, FV-NI [Line Items]
Amortized cost	2,456	2,283
Gross unrealized gains	273	458
Gross unrealized losses	(5)	(1)
Estimated fair value	2,724	2,740
State and municipal
Debt and Equity Securities, FV-NI [Line Items]
Amortized cost	3,409	3,387
Gross unrealized gains	648	878
Gross unrealized losses	(19)	(9)
Estimated fair value	4,038	4,256
Mortgage and asset-backed
Debt and Equity Securities, FV-NI [Line Items]
Amortized cost	3,725	3,652
Gross unrealized gains	153	171
Gross unrealized losses	(63)	(71)
Estimated fair value	3,815	3,752
Government and agencies
Debt and Equity Securities, FV-NI [Line Items]
Amortized cost	1,166	1,169
Gross unrealized gains	112	184
Gross unrealized losses	(3)	0
Estimated fair value	$ 1,275	$ 1,353