INVESTMENTS - Carrying Value and Fair Value of HTM Debt Securities by Contractual Maturity Dates (Details) - USD ($) $ in Millions	Sep. 30, 2022	Jun. 30, 2022	Dec. 31, 2021	Sep. 30, 2021	Jun. 30, 2021	Dec. 31, 2020
Held-to-maturity Securities, Debt Maturities, Net Carrying Amount;
Amortized cost	$ 267,864		$ 216,963
Held-to-maturity Securities, Debt Maturities, Fair Value;
Fair value	239,807		216,038
Allowance for credit losses on HTM debt securities	115	$ 105	87	$ 73	$ 83	$ 86
Mortgage-backed securities
Held-to-maturity Securities, Debt Maturities, Net Carrying Amount;
Due within 1 year, amortized cost	32		152
After 1 but within 5 years, amortized cost	683		684
After 5 but within 10 years, amortized cost	1,520		1,655
After 10 years, amortized cost	88,352		63,200
Amortized cost	90,587		65,691
Held-to-maturity Securities, Debt Maturities, Fair Value;
Due within 1 year, fair value	32		151
After 1 but within 5 years, fair value	663		725
After 5 but within 10 years, fair value	1,386		1,739
After 10 years, fair value	77,351		63,232
Fair value	79,432		65,847
U.S. treasury securities
Held-to-maturity Securities, Debt Maturities, Net Carrying Amount;
Due within 1 year, amortized cost	0		0
After 1 but within 5 years, amortized cost	89,774		65,498
After 5 but within 10 years, amortized cost	45,195		46,321
After 10 years, amortized cost	0		0
Amortized cost	134,969		111,819
Held-to-maturity Securities, Debt Maturities, Fair Value;
Due within 1 year, fair value	0		0
After 1 but within 5 years, fair value	81,540		64,516
After 5 but within 10 years, fair value	38,757		45,701
After 10 years, fair value	0		0
Fair value	120,297		110,217
State and municipal
Held-to-maturity Securities, Debt Maturities, Net Carrying Amount;
Due within 1 year, amortized cost	41		51
After 1 but within 5 years, amortized cost	121		166
After 5 but within 10 years, amortized cost	935		908
After 10 years, amortized cost	8,118		7,798
Amortized cost	9,215		8,923
Held-to-maturity Securities, Debt Maturities, Fair Value;
Due within 1 year, fair value	41		50
After 1 but within 5 years, fair value	120		170
After 5 but within 10 years, fair value	880		951
After 10 years, fair value	7,081		8,329
Fair value	8,122		9,500
Foreign government
Held-to-maturity Securities, Debt Maturities, Net Carrying Amount;
Due within 1 year, amortized cost	0		292
After 1 but within 5 years, amortized cost	2,014		1,359
After 5 but within 10 years, amortized cost	0		0
After 10 years, amortized cost	0		0
Amortized cost	2,014		1,651
Held-to-maturity Securities, Debt Maturities, Fair Value;
Due within 1 year, fair value	0		291
After 1 but within 5 years, fair value	1,899		1,328
After 5 but within 10 years, fair value	0		0
After 10 years, fair value	0		0
Fair value	1,899		1,619
All other
Held-to-maturity Securities, Debt Maturities, Net Carrying Amount;
Due within 1 year, amortized cost	0		0
After 1 but within 5 years, amortized cost	0		0
After 5 but within 10 years, amortized cost	11,857		11,520
After 10 years, amortized cost	19,222		17,359
Amortized cost	31,079		28,879
Held-to-maturity Securities, Debt Maturities, Fair Value;
Due within 1 year, fair value	0		0
After 1 but within 5 years, fair value	0		0
After 5 but within 10 years, fair value	11,603		11,515
After 10 years, fair value	18,454		17,340
Fair value	$ 30,057		$ 28,855