INVESTMENTS - Carrying Value and Fair Value of HTM Debt Securities by Contractual Maturity Dates (Details) - USD ($) $ in Millions	Mar. 31, 2024	Dec. 31, 2023
Held-to-maturity Securities, Debt Maturities, Net Carrying Amount;
Amortized cost, net	$ 252,459	$ 254,247
Held-to-maturity Securities, Debt Maturities, Fair Value;
Fair value	231,374	235,001
Allowance for credit losses on HTM debt securities	106	95
Mortgage-backed securities
Held-to-maturity Securities, Debt Maturities, Net Carrying Amount;
Due within 1 year, amortized cost	21
After 1 but within 5 years, amortized cost	1,313
After 5 but within 10 years, amortized cost	588
After 10 years, amortized cost	77,577
Amortized cost, net	79,499	81,033
Held-to-maturity Securities, Debt Maturities, Fair Value;
Due within 1 year, fair value	21
After 1 but within 5 years, fair value	1,242
After 5 but within 10 years, fair value	531
After 10 years, fair value	67,522
Fair value	69,316	72,283
U.S. treasury securities
Held-to-maturity Securities, Debt Maturities, Net Carrying Amount;
Due within 1 year, amortized cost	25,638
After 1 but within 5 years, amortized cost	106,129
After 5 but within 10 years, amortized cost	0
After 10 years, amortized cost	0
Amortized cost, net	131,767	131,776
Held-to-maturity Securities, Debt Maturities, Fair Value;
Due within 1 year, fair value	24,777
After 1 but within 5 years, fair value	96,726
After 5 but within 10 years, fair value	0
After 10 years, fair value	0
Fair value	121,503	121,868
State and municipal
Held-to-maturity Securities, Debt Maturities, Net Carrying Amount;
Due within 1 year, amortized cost	28
After 1 but within 5 years, amortized cost	116
After 5 but within 10 years, amortized cost	1,460
After 10 years, amortized cost	7,464
Amortized cost, net	9,068	9,182
Held-to-maturity Securities, Debt Maturities, Fair Value;
Due within 1 year, fair value	27
After 1 but within 5 years, fair value	114
After 5 but within 10 years, fair value	1,403
After 10 years, fair value	6,992
Fair value	8,536	8,778
Foreign government
Held-to-maturity Securities, Debt Maturities, Net Carrying Amount;
Due within 1 year, amortized cost	1,983
After 1 but within 5 years, amortized cost	279
After 5 but within 10 years, amortized cost	0
After 10 years, amortized cost	0
Amortized cost, net	2,262	2,210
Held-to-maturity Securities, Debt Maturities, Fair Value;
Due within 1 year, fair value	1,941
After 1 but within 5 years, fair value	273
After 5 but within 10 years, fair value	0
After 10 years, fair value	0
Fair value	2,214	$ 2,152
All other
Held-to-maturity Securities, Debt Maturities, Net Carrying Amount;
Due within 1 year, amortized cost	0
After 1 but within 5 years, amortized cost	1
After 5 but within 10 years, amortized cost	9,156
After 10 years, amortized cost	20,706
Amortized cost, net	29,863
Held-to-maturity Securities, Debt Maturities, Fair Value;
Due within 1 year, fair value	0
After 1 but within 5 years, fair value	1
After 5 but within 10 years, fair value	9,163
After 10 years, fair value	20,641
Fair value	$ 29,805

Amount, excluding accrued interest, of allowance for credit loss on investment in debt security measured at amortized cost (held-to-maturity).

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Amount excluding accrued interest, after allowance for credit loss, of investment in debt security measured at amortized cost (held-to-maturity) with single maturity date and allocated without single maturity date, maturing after tenth fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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