Investment Securities - Amortized Cost and Fair Value of Available-for-Sale Investment Securities Portfolio (Details) - USD ($) $ in Thousands	Dec. 31, 2024	Dec. 31, 2023
Available-for-Sale
Amortized Cost	$ 8,480,508	$ 7,684,889
Unrealized Gains	6,987	4,607
Unrealized Losses	(897,516)	(874,143)
Basis Adjustments	(131,520)	(102,298)
Fair Value	7,458,459	6,713,055
U.S. Treasury
Available-for-Sale
Amortized Cost	261,421	449,817
Unrealized Gains	67	154
Unrealized Losses	(12,659)	(11,941)
Basis Adjustments	(49,816)	(41,297)
Fair Value	199,013	396,733
U.S. government-sponsored entities and agencies
Available-for-Sale
Amortized Cost	1,521,610	1,487,879
Unrealized Gains	7	33
Unrealized Losses	(181,360)	(192,717)
Basis Adjustments	(82,351)	(63,931)
Fair Value	1,257,906	1,231,264
Mortgage-backed securities
Available-for-Sale
Amortized Cost	5,861,067	4,835,319
Unrealized Gains	6,005	3,093
Unrealized Losses	(662,181)	(621,852)
Basis Adjustments	0	0
Fair Value	5,204,891	4,216,560
States and political subdivisions
Available-for-Sale
Amortized Cost	510,630	554,509
Unrealized Gains	148	878
Unrealized Losses	(25,881)	(23,057)
Basis Adjustments	647	2,930
Fair Value	485,544	535,260
Pooled trust preferred securities
Available-for-Sale
Amortized Cost	13,807	13,797
Unrealized Gains	0	0
Unrealized Losses	(2,485)	(2,460)
Basis Adjustments	0	0
Fair Value	11,322	11,337
Other securities
Available-for-Sale
Amortized Cost	311,973	343,568
Unrealized Gains	760	449
Unrealized Losses	(12,950)	(22,116)
Basis Adjustments	0	0
Fair Value	$ 299,783	$ 321,901

Debt Securities, Available-For-Sale, Accumulated Basis Adjustments, Before Tax

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- Definition

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).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-2

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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).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-2

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- Definition

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).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 30
-Name Accounting Standards Codification
-Section 45
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479130/326-30-45-1

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- Definition

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).

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 326
-SubTopic 30
-Name Accounting Standards Codification
-Section 45
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479130/326-30-45-1

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