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INVESTMENTS - Carrying Value and Fair Value of HTM Debt Securities by Contractual Maturity Dates (Details) - USD ($) $ in Millions	Mar. 31, 2025	Dec. 31, 2024	Mar. 31, 2024	Dec. 31, 2023
Held-to-maturity Securities, Debt Maturities, Net Carrying Amount;
Amortized cost, net	$ 220,385	$ 242,382
Held-to-maturity Securities, Debt Maturities, Fair Value;
Fair value	205,187	224,410
Allowance for credit losses on HTM debt securities	130	137	$ 106	$ 95
Mortgage-backed securities
Held-to-maturity Securities, Debt Maturities, Net Carrying Amount;
Due within 1 year, amortized cost	192
After 1 but within 5 years, amortized cost	998
After 5 but within 10 years, amortized cost	1,233
After 10 years, amortized cost	69,777
Amortized cost, net	72,200	73,789
Held-to-maturity Securities, Debt Maturities, Fair Value;
Due within 1 year, fair value	191
After 1 but within 5 years, fair value	960
After 5 but within 10 years, fair value	1,153
After 10 years, fair value	60,858
Fair value	63,162	63,359
U.S. treasury securities
Held-to-maturity Securities, Debt Maturities, Net Carrying Amount;
Due within 1 year, amortized cost	24,594
After 1 but within 5 years, amortized cost	81,540
After 5 but within 10 years, amortized cost	0
After 10 years, amortized cost	0
Amortized cost, net	106,134	126,142
Held-to-maturity Securities, Debt Maturities, Fair Value;
Due within 1 year, fair value	24,199
After 1 but within 5 years, fair value	76,510
After 5 but within 10 years, fair value	0
After 10 years, fair value	0
Fair value	100,709	119,208
State and municipal
Held-to-maturity Securities, Debt Maturities, Net Carrying Amount;
Due within 1 year, amortized cost	32
After 1 but within 5 years, amortized cost	173
After 5 but within 10 years, amortized cost	1,942
After 10 years, amortized cost	6,677
Amortized cost, net	8,824	8,903
Held-to-maturity Securities, Debt Maturities, Fair Value;
Due within 1 year, fair value	31
After 1 but within 5 years, fair value	172
After 5 but within 10 years, fair value	1,861
After 10 years, fair value	6,057
Fair value	8,121	8,262
Foreign government
Held-to-maturity Securities, Debt Maturities, Net Carrying Amount;
Due within 1 year, amortized cost	153
After 1 but within 5 years, amortized cost	524
After 5 but within 10 years, amortized cost	3
After 10 years, amortized cost	0
Amortized cost, net	680	988
Held-to-maturity Securities, Debt Maturities, Fair Value;
Due within 1 year, fair value	153
After 1 but within 5 years, fair value	534
After 5 but within 10 years, fair value	3
After 10 years, fair value	0
Fair value	690	$ 991
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	9,056
After 10 years, amortized cost	23,491
Amortized cost, net	32,547
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	9,057
After 10 years, fair value	23,448
Fair value	$ 32,505