Investment Securities - Amortized Cost and Fair Value of Available-for-Sale Investment Securities Portfolio (Details) - USD ($) $ in Thousands	Mar. 31, 2025	Dec. 31, 2024
Available-for-Sale
Total	$ 8,643,126	$ 8,480,508
Unrealized Gains	20,152	6,987
Unrealized Losses	(796,933)	(897,516)
Basis adjustments	(112,374)	(131,520)
Fair Value	7,753,971	7,458,459
U.S. Treasury
Available-for-Sale
Total	261,345	261,421
Unrealized Gains	87	67
Unrealized Losses	(10,931)	(12,659)
Basis adjustments	(45,964)	(49,816)
Fair Value	204,537	199,013
U.S. government-sponsored entities and agencies
Available-for-Sale
Total	1,554,502	1,521,610
Unrealized Gains	238	7
Unrealized Losses	(161,684)	(181,360)
Basis adjustments	(68,253)	(82,351)
Fair Value	1,324,803	1,257,906
Mortgage-backed securities
Available-for-Sale
Total	6,064,171	5,861,067
Unrealized Gains	18,649	6,005
Unrealized Losses	(582,801)	(662,181)
Basis adjustments	0	0
Fair Value	5,500,019	5,204,891
States and political subdivisions
Available-for-Sale
Total	466,473	510,630
Unrealized Gains	213	148
Unrealized Losses	(29,073)	(25,881)
Basis adjustments	1,843	647
Fair Value	439,456	485,544
Pooled trust preferred securities
Available-for-Sale
Total	13,809	13,807
Unrealized Gains	0	0
Unrealized Losses	(2,498)	(2,485)
Basis adjustments	0	0
Fair Value	11,311	11,322
Other securities
Available-for-Sale
Total	282,826	311,973
Unrealized Gains	965	760
Unrealized Losses	(9,946)	(12,950)
Basis adjustments	0	0
Fair Value	$ 273,845	$ 299,783

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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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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