Investment Securities - Schedule of Contractual Maturities of Investment Securities (Details) - USD ($) $ in Thousands	Sep. 30, 2025	Dec. 31, 2024	Sep. 30, 2024
Available-for-sale securities
Due in one year or less, amortized cost	$ 58,284	$ 89,578	$ 150,539
Due in one to five years, amortized cost	160,939	157,883	168,856
Due in five to ten years, amortized cost	89,505	89,125	91,620
Due after ten years, amortized cost	26,992	24,674	23,834
Amortized Cost	5,702,349	4,725,539	4,320,843
Due in one year or less, fair value	58,315	89,392	150,627
Due in one to five years, fair value	159,081	153,325	164,650
Due in five to ten years, fair value	87,359	84,240	89,220
Due after ten years, fair value	24,408	21,650	21,809
Fair Value	5,274,124	4,141,482	3,912,232
Held-to-maturity securities
Due in one year or less, amortized cost	44,853	18,929	12,026
Due in one to five years, amortized cost	81,277	110,897	110,330
Due in five to ten years, amortized cost	91,067	71,846	84,580
Due after ten years, amortized cost	302,624	329,734	329,808
Amortized Cost	3,438,801	3,613,720	3,677,899
Less: Allowance for credit losses	(395)	(457)	(479)
Held-to-maturity securities, net of allowance for credit losses	3,438,406	3,613,263	3,677,420
Due in one year or less, fair value	44,288	18,658	11,883
Due in one to five years, fair value	81,174	108,056	108,416
Due in five to ten years, fair value	87,541	70,277	83,918
Due after ten years, fair value	245,188	258,379	271,954
Fair Value	2,860,970	2,910,550	3,121,820
Mortgage-backed
Available-for-sale securities
Mortgage-backed, amortized cost	5,366,629	4,364,279	3,885,994
Mortgage-backed, fair value	4,944,961	3,792,875	3,485,926
Held-to-maturity securities
Mortgage-backed, amortized cost	2,918,980	3,082,314	3,141,155
Mortgage-backed, fair value	$ 2,402,779	$ 2,455,180	$ 2,645,649