SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Accounting Changes Narrative (Details) - USD ($) $ in Millions	3 Months Ended
	Jun. 30, 2022	Dec. 31, 2023	Jan. 01, 2023	Dec. 31, 2022		Dec. 31, 2021		Dec. 31, 2020
New Accounting Pronouncements or Change in Accounting Principle
Allowance for credit losses on loans (ACLL)		$ (18,145)		$ (16,974)		$ (16,455)		$ (24,956)
Other assets		95,963		103,743
Stockholders’ equity		206,251		201,838		202,672
Deferred tax assets		(29,608)		(27,672)
Decrease to other liabilities		(75,835)		(87,873)
Retained earnings
New Accounting Pronouncements or Change in Accounting Principle
Stockholders’ equity		198,905		194,734		184,948		168,272
Accumulated other comprehensive income (loss)
New Accounting Pronouncements or Change in Accounting Principle
Stockholders’ equity		$ (44,800)		(47,062)		(38,765)		(32,058)
Macroeconomic Uncertainty
New Accounting Pronouncements or Change in Accounting Principle
Net (decrease) increase in allowance for credit losses	$ 800
Change in Accounting Method Accounted for as Change in Estimate
New Accounting Pronouncements or Change in Accounting Principle
Net (decrease) increase in allowance for credit losses	$ (300)
Cumulative effect of adoption
New Accounting Pronouncements or Change in Accounting Principle
Allowance for credit losses on loans (ACLL)			$ 352	352
Other assets			40
Deferred tax assets			102
Decrease to other liabilities			39
Cumulative effect of adoption | Retained earnings
New Accounting Pronouncements or Change in Accounting Principle
Stockholders’ equity			290	290	[1]	0	[1]	0	[1]
Cumulative effect of adoption | Accumulated other comprehensive income (loss)
New Accounting Pronouncements or Change in Accounting Principle
Stockholders’ equity			$ 27	$ 27	[1]	$ 0	[1]	$ 0	[1]

[1] See Note 1 for additional details.