Investment Securities - Schedule of Amortized Cost, Gross Unrealized Gains and Losses, and Estimated Fair Values of Investment Securities (Details) - USD ($) $ in Thousands	Jun. 30, 2025	Dec. 31, 2024
Investment securities held to maturity:
Amortized Cost	$ 2,502,639	$ 2,581,469
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(26,350)	(56,944)
Fair Value	2,476,289	2,524,525
Investment securities available for sale:
Amortized Cost	8,142,396	8,079,918
Gross Unrealized Gains	70,244	9,025
Gross Unrealized Losses	(413,816)	(537,925)
Fair Value	7,798,824	7,551,018
Accrued interest receivable on investment securities held to maturity	5,500	5,700
Discount included in amortized cost of investment securities HTM	(614,600)	(649,700)
Accrued interest receivable on investment securities available for sale	$ 29,800	$ 29,500
Debt Securities, Available-for-Sale, Accrued Interest, after Allowance for Credit Loss, Statement of Financial Position [Extensible Enumeration]	Other assets	Other assets
U.S. Treasury securities
Investment securities available for sale:
Amortized Cost	$ 1,220,809	$ 1,214,363
Gross Unrealized Gains	20,119	3,203
Gross Unrealized Losses	(2)	(4,824)
Fair Value	1,240,926	1,212,742
U.S. Government agency securities
Investment securities available for sale:
Amortized Cost	29,995	29,993
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(284)	(830)
Fair Value	29,711	29,163
Mortgage-backed securities issued by U.S. Government agencies
Investment securities available for sale:
Amortized Cost	1,551,556	1,583,331
Gross Unrealized Gains	6,540	848
Gross Unrealized Losses	(101,208)	(121,389)
Fair Value	1,456,888	1,462,790
Mortgage-backed securities issued by U.S. Government sponsored enterprises
Investment securities held to maturity:
Amortized Cost	2,502,639	2,581,469
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(26,350)	(56,944)
Fair Value	2,476,289	2,524,525
Investment securities available for sale:
Amortized Cost	2,239,222	2,294,700
Gross Unrealized Gains	1,792	250
Gross Unrealized Losses	(199,625)	(260,915)
Fair Value	2,041,389	2,034,035
Collateralized mortgage obligations issued by U.S. Government agencies or sponsored enterprises
Investment securities available for sale:
Amortized Cost	623,963	657,453
Gross Unrealized Gains	119	0
Gross Unrealized Losses	(88,413)	(107,252)
Fair Value	535,669	550,201
Commercial mortgage-backed securities issued by U.S. Government agencies or sponsored enterprises
Investment securities available for sale:
Amortized Cost	2,467,691	2,290,968
Gross Unrealized Gains	41,667	4,724
Gross Unrealized Losses	(24,284)	(42,576)
Fair Value	2,485,074	2,253,116
Corporate debt securities and other debt securities
Investment securities available for sale:
Amortized Cost	9,160	9,110
Gross Unrealized Gains	7	0
Gross Unrealized Losses	0	(139)
Fair Value	$ 9,167	$ 8,971

Debt Securities, Held-To-Maturity, Discount (Premium)

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