Investment Securities - Schedule of Contractual Maturities of Investment Securities (Details) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022	Sep. 30, 2022
Available-for-sale securities
Due in one year or less, amortized cost	$ 99,892	$ 119,830	$ 55,249
Due in one to five years, amortized cost	139,623	63,644	86,555
Due in five to ten years, amortized cost	43,199	115,734	115,949
Due after ten years, amortized cost	64,419	64,590	68,853
Amortized Cost	4,315,723	3,769,634	3,478,306
Due in one year or less, fair value	99,525	119,275	54,846
Due in one to five years, fair value	130,036	61,701	83,641
Due in five to ten years, fair value	38,074	105,076	105,921
Due after ten years, fair value	54,855	57,478	60,639
Fair Value	3,611,835	3,243,017	2,923,653
Held-to-maturity securities
Held-to-maturity securities, due in one year or less, amortized cost	2,248	1,340	1,173
Held-to-maturity securities, due in one to five years, amortized cost	103,104	94,705	85,423
Held-to-maturity securities, due in five to ten years, amortized cost	106,042	115,318	108,703
Held-to-maturity securities, due after ten years, amortized cost	362,183	365,510	348,026
Amortized Cost	3,909,531	3,641,055	3,390,152
Less: Allowance for credit losses	(381)	(488)	(310)
Held-to-maturity securities, net of allowance for credit losses	3,909,150	3,640,567	3,389,842
Held-to-maturity securities, due in one year or less, fair value	2,241	1,332	1,166
Held-to-maturity securities, due in one to five years, fair value	96,546	89,093	78,995
Held-to-maturity securities, due in five to ten years, fair value	100,215	113,758	104,829
Held-to-maturity securities, due after ten years, fair value	270,722	288,460	272,319
Fair Value	3,057,959	2,949,821	2,679,326
Mortgage-backed
Available-for-sale securities
Mortgage-backed, without single maturity date, amortized cost	3,968,590	3,405,836	3,151,700
Mortgage-backed, without single maturity date, fair value	3,289,345	2,899,487	2,618,606
Held-to-maturity securities
Mortgage-backed, amortized cost	3,335,954	3,064,182	2,846,827
Mortgage-backed, fair value	$ 2,588,235	$ 2,457,178	$ 2,222,017