INVESTMENT SECURITIES - Schedule of Amortized Cost and Fair Value of Securities, by Contractual Maturities (Details) - USD ($) $ in Millions	Sep. 30, 2025	Dec. 31, 2024
Amortized Cost
Available for sale, due in one year or less, amortized cost	$ 206
Available for sale, due after one year but within five years, amortized cost	424
Available for sale, due after five years but within ten years, amortized cost	62
Available for sale, due after ten years, amortized cost	21
Available for sale, with contractual maturities, amortized cost	713
Amortized Cost	3,690	$ 3,620
Fair Value
Available for sale, due in one year or less, fair value	206
Available for sale, due after one year but within five years, fair value	425
Available for sale, due after five years but within ten years, fair value	63
Available for sale, due after ten years, fair value	20
Available for sale, with contractual maturities, fair value	714
Fair Value	3,620	3,466
Amortized Cost
Held to maturity, due in one year or less, amortized cost	4
Held to maturity, due after one year but within five years, amortized cost	89
Held to maturity, due after five years but within ten years, amortized cost	239
Held to maturity, due after ten years, amortized cost	664
Held to maturity, with contractual maturities, amortized cost	996
Amortized Cost	4,049	3,979
Fair Value
Held to maturity, due in one year or less, fair value	5
Held to maturity, due after one year but within five years, fair value	86
Held to maturity, due after five years but within ten years, fair value	229
Held to maturity, due after ten years, fair value	599
Held to maturity, with contractual maturities, fair value	919
Fair Value	3,838	3,644
Agency MBS
Amortized Cost
Available-for-sale, amortized cost	773
Amortized Cost	773	714
Fair Value
Available for sale, fair value	770
Fair Value	770	694
Amortized Cost
Held to maturity, amortized cost	821
Amortized Cost	821	901
Fair Value
Held to maturity, fair value	761
Fair Value	761	806
Agency CMO
Amortized Cost
Available-for-sale, amortized cost	694
Amortized Cost	694	796
Fair Value
Available for sale, fair value	626
Fair Value	626	698
Amortized Cost
Held to maturity, amortized cost	637
Amortized Cost	637	714
Fair Value
Held to maturity, fair value	569
Fair Value	569	619
Agency commercial MBS
Amortized Cost
Available-for-sale, amortized cost	1,510
Amortized Cost	1,510	1,420
Fair Value
Available for sale, fair value	1,510
Fair Value	1,510	1,388
Amortized Cost
Held to maturity, amortized cost	1,595
Amortized Cost	1,595	1,326
Fair Value
Held to maturity, fair value	1,589
Fair Value	$ 1,589	$ 1,284