Investment Securities - Amortized Cost and Fair Value of Securities (Details) - USD ($) $ in Thousands	Mar. 31, 2025	Dec. 31, 2024
Available for sale debt securities
Amortized Cost	$ 2,091,034	$ 2,190,448
Unrealized Gains	375	406
Unrealized Losses	(232,981)	(264,338)
Total available-for-sale securities	1,858,428	1,926,516
Held to maturity securities
Amortized Cost	3,724,908	3,790,650
Unrealized Gains	209	201
Unrealized Losses	(474,842)	(528,342)
Total held-to-maturity securities	3,250,275	3,262,509
Available-for-sale investment securities
Accrued interest receivable related to available-for-sale investment securities	5,000	5,600
Accrued interest receivable related to held to maturity investment securities	6,800	6,600
Collateralized loan obligations
Available for sale debt securities
Amortized Cost	136,413	173,152
Unrealized Gains	109	323
Unrealized Losses	(19)
Total available-for-sale securities	136,503	173,475
Government agency debt securities
Available for sale debt securities
Amortized Cost		8,170
Unrealized Losses		(23)
Total available-for-sale securities		8,147
Held to maturity securities
Amortized Cost	49,104	49,267
Unrealized Losses	(4,478)	(5,398)
Total held-to-maturity securities	44,626	43,869
Residential - Government agency
Available for sale debt securities
Amortized Cost	36,376	37,473
Unrealized Gains	243
Unrealized Losses	(1,305)	(1,614)
Total available-for-sale securities	35,314	35,859
Held to maturity securities
Amortized Cost	39,912	40,888
Unrealized Losses	(5,671)	(6,579)
Total held-to-maturity securities	34,241	34,309
Residential - Government-sponsored enterprises
Available for sale debt securities
Amortized Cost	814,089	840,836
Unrealized Gains	5
Unrealized Losses	(86,677)	(102,723)
Total available-for-sale securities	727,417	738,113
Held to maturity securities
Amortized Cost	91,523	92,573
Unrealized Losses	(13,511)	(14,854)
Total held-to-maturity securities	78,012	77,719
Commercial - Government agency
Available for sale debt securities
Amortized Cost	246,139	249,348
Unrealized Losses	(50,373)	(53,223)
Total available-for-sale securities	195,766	196,125
Held to maturity securities
Amortized Cost	31,056	31,009
Unrealized Losses	(8,698)	(8,666)
Total held-to-maturity securities	22,358	22,343
Commercial - Government-sponsored enterprises
Available for sale debt securities
Amortized Cost	46,380	48,015
Unrealized Losses	(2,368)	(3,107)
Total available-for-sale securities	44,012	44,908
Held to maturity securities
Amortized Cost	1,103,962	1,114,549
Unrealized Gains	209	201
Unrealized Losses	(137,358)	(149,244)
Total held-to-maturity securities	966,813	965,506
Commercial - Non-agency
Available for sale debt securities
Amortized Cost	22,000	22,000
Unrealized Gains	5	83
Total available-for-sale securities	22,005	22,083
Government agency
Available for sale debt securities
Amortized Cost	440,756	452,038
Unrealized Gains	13
Unrealized Losses	(49,095)	(54,914)
Total available-for-sale securities	391,674	397,124
Held to maturity securities
Amortized Cost	887,439	907,565
Unrealized Losses	(111,525)	(126,020)
Total held-to-maturity securities	775,914	781,545
Government-sponsored enterprises
Available for sale debt securities
Amortized Cost	348,881	359,416
Unrealized Losses	(43,144)	(48,734)
Total available-for-sale securities	305,737	310,682
Held to maturity securities
Amortized Cost	1,467,222	1,500,212
Unrealized Losses	(187,697)	(210,721)
Total held-to-maturity securities	1,279,525	1,289,491
Debt securities issued by states and political subdivisions
Held to maturity securities
Amortized Cost	54,690	54,587
Unrealized Losses	(5,904)	(6,860)
Total held-to-maturity securities	$ 48,786	$ 47,727