INVESTMENT SECURITIES - Schedule of Investment Securities Maturity Information (Details) - USD ($) $ in Millions	Dec. 31, 2024	Dec. 31, 2023
Investment securities available for sale
Non-amortizing securities maturing in one year or less, amortized cost	$ 5,090	$ 5,674
Non-amortizing securities maturing in after one through five years, amortized cost	8,945	4,996
Non-amortizing securities maturing in after five through 10 years, amortized cost	346	408
Non-amortizing securities maturing in after 10 years, amortized cost	22	17
Amortized Cost	34,512	20,688
Non-amortizing securities maturing in one year or less, fair value	5,086	5,658
Non-amortizing securities maturing in after one through five years, fair value	8,949	4,959
Non-amortizing securities maturing in after five through 10 years, fair value	330	369
Non-amortizing securities maturing in after 10 years, fair value	22	16
Investment securities available for sale, fair value	33,750	19,936
Investment securities held to maturity
Non-amortizing securities maturing in one year or less, amortized cost	429	27
Non-amortizing securities maturing in after one through five years, amortized cost	1,299	1,636
Non-amortizing securities maturing in after five through 10 years, amortized cost	546	622
Amortized Cost	10,239	9,979
Non-amortizing securities maturing in one year or less, fair value	419	26
Non-amortizing securities maturing in after one through five years, fair value	1,208	1,508
Non-amortizing securities maturing in after five through 10 years, fair value	468	533
Investment securities held to maturity, cost, fair value	8,702	8,503
Government agency
Investment securities available for sale
Without single maturity date, amortized cost	79	120
Without single maturity date, fair value	77	117
Residential mortgage-backed securities
Investment securities available for sale
Without single maturity date, amortized cost	16,161	7,154
Without single maturity date, fair value	15,620	6,686
Investment securities held to maturity
Without single maturity date, amortized cost	4,558	4,205
Without single maturity date, fair value	3,878	3,561
Commercial mortgage-backed securities
Investment securities available for sale
Without single maturity date, amortized cost	3,869	2,319
Without single maturity date, fair value	3,666	2,131
Investment securities held to maturity
Without single maturity date, amortized cost	3,407	3,489
Without single maturity date, fair value	$ 2,729	$ 2,875