Investment Securities, Equity Securities with Readily Determinable Fair Values and Other Investments (Details) - USD ($)	Sep. 30, 2025	Dec. 31, 2024
Held-to-maturity securities
Amortized cost	$ 4,400,000	$ 4,400,000
Estimated fair value	4,400,000	4,400,000
Carrying value	4,400,000	4,400,000
Available-for-sale securities
Amortized cost	5,316,580,000	5,472,310,000
Gross unrealized gains	23,677,000	9,189,000
Gross unrealized losses	(359,915,000)	(493,583,000)
Estimated fair value, Available for sale securities	4,980,342,000	4,987,916,000
Estimated Fair Value
Available-for-sale securities
Estimated fair value, Available for sale securities	4,980,342,000	4,987,916,000
Reported Value Measurement
Available-for-sale securities
Estimated fair value, Available for sale securities	4,980,342,000	4,987,916,000
Residential mortgage-backed securities
Available-for-sale securities
Amortized cost	5,175,459,000	5,315,488,000
Gross unrealized gains	23,676,000	8,858,000
Gross unrealized losses	(353,611,000)	(489,170,000)
Residential mortgage-backed securities \| Estimated Fair Value
Available-for-sale securities
Estimated fair value, Available for sale securities	4,845,524,000	4,835,176,000
Residential mortgage-backed securities \| Reported Value Measurement
Available-for-sale securities
Estimated fair value, Available for sale securities	4,845,524,000	4,835,176,000
Mortgage-backed securities
Available-for-sale securities
Estimated fair value, Available for sale securities	880,747	1,001,184
Fannie Mae and Freddie Mac
Available-for-sale securities
Estimated fair value, Available for sale securities	3,964,777	3,833,992
States and political subdivisions
Available-for-sale securities
Amortized cost	141,121,000	156,822,000
Gross unrealized gains	1,000	331,000
Gross unrealized losses	(6,304,000)	(4,413,000)
States and political subdivisions \| Estimated Fair Value
Available-for-sale securities
Estimated fair value, Available for sale securities	134,818,000	152,740,000
States and political subdivisions \| Reported Value Measurement
Available-for-sale securities
Estimated fair value, Available for sale securities	134,818,000	152,740,000
Other Debt Obligations
Held-to-maturity securities
Amortized cost	4,400,000	4,400,000
Estimated fair value	4,400,000	4,400,000
Carrying value	$ 4,400,000	$ 4,400,000

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).

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).

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

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