INVESTMENT SECURITIES - Schedule of AFS Securities Maturities (Details) - USD ($) $ in Thousands	Sep. 30, 2026	Dec. 31, 2025
Amortized Cost
Available-for-sale, amortized cost	$ 15,557,363	$ 13,813,551
Fair  Value
Total fair value	14,885,573	13,580,285
Total AFS Investment Securities
Amortized Cost
Due within one year	1,897,189
Due after one year through five years	7,057,528
Due after five years through ten years	4,432,768
Due after ten years	2,169,878
Available-for-sale, amortized cost	15,557,363	13,813,551
Fair  Value
Due within one year	1,884,382
Due after one year through five years	6,865,362
Due after five years through ten years	4,157,770
Due after ten years	1,978,059
Total fair value	$ 14,885,573	13,580,285
Weighted-Average Yield
Due within one year	3.44%
Due after one year through five years	4.04%
Due after five years through ten years	3.92%
Due after ten years	4.12%
Weighted-average yield	3.94%
Available-for-sale, accrued interest excluded	$ 109,900	$ 91,300