Investment Securities - Schedule of Amortized Cost, Gross Unrealized Gains and Losses, and Fair Value of Investment Securities (Details) - USD ($) $ in Thousands	Jun. 30, 2025	Dec. 31, 2024
Available-for-Sale:
Available-for-Sale: Amortized Cost	$ 3,313,974	$ 2,947,415
Available-for-Sale: Gross Unrealized Gains	4,476	1,248
Available-for-Sale: Gross Unrealized Losses	(206,946)	(259,135)
Total Investment Securities Available-for-Sale	3,111,504	2,689,528
Held-to-Maturity:
Held-to-Maturity: Amortized Cost	4,441,353	4,618,543
Held-to-Maturity: Gross Unrealized Gains	72	40
Held-to-Maturity: Gross Unrealized Losses	(686,631)	(797,701)
Investment Securities Held-to-Maturity	3,754,794	3,820,882
Debt Securities Issued by the U.S. Treasury and Government Agencies
Available-for-Sale:
Available-for-Sale: Amortized Cost	248,373	257,036
Available-for-Sale: Gross Unrealized Gains	462	221
Available-for-Sale: Gross Unrealized Losses	(5,120)	(8,185)
Total Investment Securities Available-for-Sale	243,715	249,072
Held-to-Maturity:
Held-to-Maturity: Amortized Cost	131,932	131,868
Held-to-Maturity: Gross Unrealized Gains	0	0
Held-to-Maturity: Gross Unrealized Losses	(10,754)	(14,927)
Investment Securities Held-to-Maturity	121,178	116,941
Debt Securities Issued by States and Political Subdivisions
Available-for-Sale:
Available-for-Sale: Amortized Cost	72,943	73,208
Available-for-Sale: Gross Unrealized Gains	0	0
Available-for-Sale: Gross Unrealized Losses	(6,983)	(9,349)
Total Investment Securities Available-for-Sale	65,960	63,859
Debt Securities Issued by U.S. Government-Sponsored Enterprises
Available-for-Sale:
Available-for-Sale: Amortized Cost	1,005	1,505
Available-for-Sale: Gross Unrealized Gains	0	0
Available-for-Sale: Gross Unrealized Losses	(20)	(41)
Total Investment Securities Available-for-Sale	985	1,464
Debt Securities Issued by Corporations
Available-for-Sale:
Available-for-Sale: Amortized Cost	752,354	703,579
Available-for-Sale: Gross Unrealized Gains	1,640	376
Available-for-Sale: Gross Unrealized Losses	(25,152)	(32,280)
Total Investment Securities Available-for-Sale	728,842	671,675
Held-to-Maturity:
Held-to-Maturity: Amortized Cost	10,354	10,490
Held-to-Maturity: Gross Unrealized Gains	0	0
Held-to-Maturity: Gross Unrealized Losses	(1,827)	(2,156)
Investment Securities Held-to-Maturity	8,527	8,334
Total Collateralized Mortgage Obligations
Available-for-Sale:
Available-for-Sale: Amortized Cost	1,582,011	1,356,995
Available-for-Sale: Gross Unrealized Gains	1,462	521
Available-for-Sale: Gross Unrealized Losses	(117,636)	(138,822)
Total Investment Securities Available-for-Sale	1,465,837	1,218,694
Held-to-Maturity:
Held-to-Maturity: Amortized Cost	2,504,103	2,601,599
Held-to-Maturity: Gross Unrealized Gains	3	3
Held-to-Maturity: Gross Unrealized Losses	(408,663)	(469,360)
Investment Securities Held-to-Maturity	2,095,443	2,132,242
Residential - Government Agencies or Sponsored Enterprises
Available-for-Sale:
Available-for-Sale: Amortized Cost	1,191,950	1,050,299
Available-for-Sale: Gross Unrealized Gains	877	322
Available-for-Sale: Gross Unrealized Losses	(95,458)	(115,401)
Total Investment Securities Available-for-Sale	1,097,369	935,220
Held-to-Maturity:
Held-to-Maturity: Amortized Cost	2,092,255	2,185,210
Held-to-Maturity: Gross Unrealized Gains	3	3
Held-to-Maturity: Gross Unrealized Losses	(325,650)	(377,149)
Investment Securities Held-to-Maturity	1,766,608	1,808,064
Commercial - Government Agencies or Sponsored Enterprises
Available-for-Sale:
Available-for-Sale: Amortized Cost	354,093	306,696
Available-for-Sale: Gross Unrealized Gains	535	199
Available-for-Sale: Gross Unrealized Losses	(22,167)	(23,421)
Total Investment Securities Available-for-Sale	332,461	283,474
Held-to-Maturity:
Held-to-Maturity: Amortized Cost	411,848	416,389
Held-to-Maturity: Gross Unrealized Gains	0	0
Held-to-Maturity: Gross Unrealized Losses	(83,013)	(92,211)
Investment Securities Held-to-Maturity	328,835	324,178
Commercial - Non-Agency
Available-for-Sale:
Available-for-Sale: Amortized Cost	35,968
Available-for-Sale: Gross Unrealized Gains	50
Available-for-Sale: Gross Unrealized Losses	(11)
Total Investment Securities Available-for-Sale	36,007
Total Mortgage-Backed Securities
Available-for-Sale:
Available-for-Sale: Amortized Cost	657,288	555,092
Available-for-Sale: Gross Unrealized Gains	912	130
Available-for-Sale: Gross Unrealized Losses	(52,035)	(70,458)
Total Investment Securities Available-for-Sale	606,165	484,764
Held-to-Maturity:
Held-to-Maturity: Amortized Cost	1,794,964	1,874,586
Held-to-Maturity: Gross Unrealized Gains	69	37
Held-to-Maturity: Gross Unrealized Losses	(265,387)	(311,258)
Investment Securities Held-to-Maturity	1,529,646	1,563,365
Residential - Government Agencies or Sponsored Agencies
Available-for-Sale:
Available-for-Sale: Amortized Cost	657,288	555,092
Available-for-Sale: Gross Unrealized Gains	912	130
Available-for-Sale: Gross Unrealized Losses	(52,035)	(70,458)
Total Investment Securities Available-for-Sale	606,165	484,764
Held-to-Maturity:
Held-to-Maturity: Amortized Cost	1,784,975	1,864,591
Held-to-Maturity: Gross Unrealized Gains	69	37
Held-to-Maturity: Gross Unrealized Losses	(263,552)	(309,093)
Investment Securities Held-to-Maturity	1,521,492	1,555,535
Commercial - Government Agencies or Sponsored Enterprises
Held-to-Maturity:
Held-to-Maturity: Amortized Cost	9,989	9,995
Held-to-Maturity: Gross Unrealized Gains	0	0
Held-to-Maturity: Gross Unrealized Losses	(1,835)	(2,165)
Investment Securities Held-to-Maturity	$ 8,154	$ 7,830

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, before 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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Amount excluding accrued interest, before allowance for credit loss, of investment in debt security measured at amortized cost (held-to-maturity).

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Amount of accumulated unrecognized gain on investment in debt security measured at amortized cost (held-to-maturity).

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Amount of accumulated unrealized loss on investment in debt security measured at amortized cost (held-to-maturity).

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

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