Securities - Amortized Cost and Fair Value of Securities Available for Sale and Held for Investment (Details) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
Available-for-Sale Debt Securities
Available for sale, amortized cost, total	$ 2,128,508	$ 2,119,303
Available for sale, gross unrealized gains	681	1,101
Available for sale, gross unrealized losses	(287,344)	(248,662)
Available for sale, fair value	1,841,845	1,871,742
Held-to-Maturity Debt Securities
Held to maturity, amortized cost, total	691,404	747,408
Held to maturity, gross unrealized gains	0	64
Held to maturity, gross unrealized losses	(154,186)	(129,731)
Held to maturity, fair value	537,218	617,741
U.S. Treasury securities and obligations of U.S. government agencies
Available-for-Sale Debt Securities
Available for sale, amortized cost, total	39,388	13,813
Available for sale, gross unrealized gains	2	173
Available for sale, gross unrealized losses	(954)	(339)
Available for sale, fair value	38,436	13,647
Mortgage-backed securities and collateralized mortgage obligations of U.S. government-sponsored entities
Available-for-Sale Debt Securities
Available for sale, amortized cost, total	1,593,306	1,561,197
Available for sale, gross unrealized gains	58	539
Available for sale, gross unrealized losses	(266,725)	(223,083)
Available for sale, fair value	1,326,639	1,338,653
Held-to-Maturity Debt Securities
Held to maturity, amortized cost, total		747,408
Held to maturity, gross unrealized gains		64
Held to maturity, gross unrealized losses		(129,731)
Held to maturity, fair value		617,741
Private mortgage-backed securities and collateralized mortgage obligations
Available-for-Sale Debt Securities
Available for sale, amortized cost, total	139,089	179,148
Available for sale, gross unrealized gains	25	70
Available for sale, gross unrealized losses	(13,927)	(12,831)
Available for sale, fair value	125,187	166,387
Collateralized loan obligations
Available-for-Sale Debt Securities
Available for sale, amortized cost, total	307,664	313,155
Available for sale, gross unrealized gains	0	0
Available for sale, gross unrealized losses	(3,496)	(10,251)
Available for sale, fair value	304,168	302,904
Obligations of state and political subdivisions
Available-for-Sale Debt Securities
Available for sale, amortized cost, total	21,768	29,350
Available for sale, gross unrealized gains	0	122
Available for sale, gross unrealized losses	(2,116)	(1,731)
Available for sale, fair value	19,652	27,741
Other debt securities
Available-for-Sale Debt Securities
Available for sale, amortized cost, total	27,293	22,640
Available for sale, gross unrealized gains	596	197
Available for sale, gross unrealized losses	(126)	(427)
Available for sale, fair value	27,763	$ 22,410
Mortgage-backed securities and collateralized mortgage obligations of U.S. government-sponsored entities
Held-to-Maturity Debt Securities
Held to maturity, amortized cost, total	691,404
Held to maturity, gross unrealized gains	0
Held to maturity, gross unrealized losses	(154,186)
Held to maturity, fair value	$ 537,218

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amount, before tax, of unrealized loss in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amortized cost excluding accrued interest, after allowance for credit loss, of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amount excluding accrued interest, of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Fair value of investment in debt security measured at amortized cost (held-to-maturity).

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