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INVESTMENTS - Carrying Value and Fair Value of HTM Debt Securities by Contractual Maturity Dates (Details) - USD ($) $ in Millions	Mar. 31, 2026	Dec. 31, 2025	Mar. 31, 2025	Dec. 31, 2024
Held-to-maturity Securities, Debt Maturities, Net Carrying Amount;
Amortized cost, net	$ 178,503	$ 189,831
Held-to-maturity Securities, Debt Maturities, Fair Value;
Fair value	167,857	179,520
Allowance for credit losses on HTM debt securities	116	146	$ 130	$ 137
Mortgage-backed securities
Held-to-maturity Securities, Debt Maturities, Net Carrying Amount;
Due within 1 year, amortized cost	0
After 1 but within 5 years, amortized cost	1,066
After 5 but within 10 years, amortized cost	1,236
After 10 years, amortized cost	63,149
Amortized cost, net	65,451	66,919
Held-to-maturity Securities, Debt Maturities, Fair Value;
Due within 1 year, fair value	0
After 1 but within 5 years, fair value	1,027
After 5 but within 10 years, fair value	1,167
After 10 years, fair value	56,031
Fair value	58,225	59,994
U.S. treasury securities
Held-to-maturity Securities, Debt Maturities, Net Carrying Amount;
Due within 1 year, amortized cost	35,893
After 1 but within 5 years, amortized cost	45,656
After 5 but within 10 years, amortized cost	0
After 10 years, amortized cost	0
Amortized cost, net	81,549	89,494
Held-to-maturity Securities, Debt Maturities, Fair Value;
Due within 1 year, fair value	35,414
After 1 but within 5 years, fair value	43,291
After 5 but within 10 years, fair value	0
After 10 years, fair value	0
Fair value	78,705	86,484
State and municipal
Held-to-maturity Securities, Debt Maturities, Net Carrying Amount;
Due within 1 year, amortized cost	16
After 1 but within 5 years, amortized cost	329
After 5 but within 10 years, amortized cost	2,390
After 10 years, amortized cost	5,782
Amortized cost, net	8,517	8,608
Held-to-maturity Securities, Debt Maturities, Fair Value;
Due within 1 year, fair value	16
After 1 but within 5 years, fair value	328
After 5 but within 10 years, fair value	2,278
After 10 years, fair value	5,330
Fair value	7,952	8,179
Foreign government
Held-to-maturity Securities, Debt Maturities, Net Carrying Amount;
Due within 1 year, amortized cost	287
After 1 but within 5 years, amortized cost	333
After 5 but within 10 years, amortized cost	0
After 10 years, amortized cost	0
Amortized cost, net	620	790
Held-to-maturity Securities, Debt Maturities, Fair Value;
Due within 1 year, fair value	294
After 1 but within 5 years, fair value	343
After 5 but within 10 years, fair value	0
After 10 years, fair value	0
Fair value	637	$ 810
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	0
After 5 but within 10 years, amortized cost	2,100
After 10 years, amortized cost	20,266
Amortized cost, net	22,366
Held-to-maturity Securities, Debt Maturities, Fair Value;
Due within 1 year, fair value	0
After 1 but within 5 years, fair value	0
After 5 but within 10 years, fair value	2,099
After 10 years, fair value	20,239
Fair value	$ 22,338