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Amortized cost of investment in debt security, excluding accrued interest measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), with single maturity date and allocated without single maturity date, maturing in rolling sixth through tenth fiscal year following latest fiscal year. For interim and annual periods when interim period is reported on rolling approach, from latest statement of financial position date.

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Fair value of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), with single maturity date and allocated without single maturity date, maturing after rolling tenth fiscal year following latest fiscal year. For interim and annual periods when interim period is reported on rolling approach, from latest statement of financial position date.

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Fair value of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), without single maturity date and not allocated over maturity grouping.

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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 of realized gain 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 of realized loss 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 of restricted 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, after allowance for credit loss, of investment in debt security measured at amortized cost (held-to-maturity) with single maturity date and allocated without single maturity date, maturing in next rolling fiscal year following current statement of financial position date. For interim and annual periods when interim period is reported on rolling approach.

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Amount excluding accrued interest, after 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), with single maturity date and allocated without single maturity date, maturing in next rolling fiscal year following latest fiscal year. For interim and annual periods when interim period is reported on rolling approach, from latest statement of financial position date.

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Fair value of investment in debt security measured at amortized cost (held-to-maturity), with single maturity date and allocated without single maturity date, maturing in second through fifth rolling fiscal year following latest fiscal year. For interim and annual periods when interim period is reported on rolling approach, from latest statement of financial position date.

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

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Amount of cash inflow from sale 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 of cash inflow from sale of investment in mortgage-backed security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Investment Securities, Equity Securities with Readily Determinable Fair Values and Other Investments (Contractual Maturities and Estimated Fair Values) (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022	Dec. 31, 2022
Amortized Cost
Due in one year or less, held-to-maturity debt securities amortized cost	$ 2,075,000		$ 2,075,000
Due after one year through five years, held-to-maturity debt securities amortized cost	1,325,000		1,325,000
Amortized cost, held-to-maturity debt securities	3,400,000		3,400,000		$ 3,400,000
Fair Value
Due in one year or less, held-to-maturity debt securities, Estimated fair value	2,075,000		2,075,000
Due after one year through five years, held-to-maturity debt securities, Estimated fair value	1,325,000		1,325,000
Estimated fair value	3,400,000		3,400,000		3,400,000
Available-for-sale debt securities amortized cost disclosures
Due after five years through ten years, available-for-sale debt securities amortized cost	440,000		440,000
Due after ten years, available-for-sale debt securities amortized cost	160,678,000		160,678,000
Residential mortgage-backed securities, amortized cost	5,227,139,000		5,227,139,000
Amortized cost, Available-for-sale securities	5,388,257,000		5,388,257,000		5,018,996,000
Available for sale debt securities, Estimated Fair Value Disclosures
Due after five years through ten years, available-for-sale debt securities, Estimated Fair Value	431,000		431,000
Due after ten years, available-for-sale debt securities, Estimated Fair Value	145,907,000		145,907,000
Residential mortgage-backed securities, Estimated Fair Value	4,545,600,000		4,545,600,000
Estimated fair value, Available for sale securities	4,691,938,000		4,691,938,000		$ 4,417,796,000
Available for sale debt securities, Estimated Fair Value Disclosures
Proceeds from sales and calls of available for sale securities	1,595,000	$ 800,000	2,045,000	$ 800,000
Proceeds from sales of mortgage-backed securities	0	0	0	0
Gross gains realized on sales	0	0	0	0
Gross losses realized on sales	3	$ 0	3	$ 0
Collateral Pledged
Available-for-sale debt securities amortized cost disclosures
Amortized cost, Available-for-sale securities	1,797,588,000		1,797,588,000
Available for sale debt securities, Estimated Fair Value Disclosures
Fair value of available for sale investment securities pledged	$ 1,501,836,000		$ 1,501,836,000