Fair Value Measurements (Estimated Fair Values of Financial Instruments) (Details) - USD ($) $ in Thousands	Jun. 30, 2022	Dec. 31, 2021
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Held to maturity securities	$ 2,752,012	$ 1,565,751
Loans held for sale	21,496	41,022
Derivative financial instruments	72,408	6,908
Derivative financial instruments	3,102	22,244
Total Fair Value [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Cash, interest-bearing bank deposits, and federal funds sold	1,569,470	4,231,836
Available for sale securities	5,779,381	6,986,698
Held to maturity securities	2,615,798	1,631,482
Loans, net	21,537,820	20,733,821
Loans held for sale	44,253	93,069
Derivative financial instruments	78,793	75,867
Deposits	29,830,503	30,432,646
Federal funds purchased	2,350	1,850
Securities sold under agreements to repurchase	427,661	563,211
FHLB short-term borrowings	200,000	1,119,026
Long-term debt	240,091	253,677
Derivative financial instruments	118,652	35,046
Total Fair Value [Member] \| Level 1 [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Cash, interest-bearing bank deposits, and federal funds sold	1,569,470	4,231,836
Federal funds purchased	2,350	1,850
Securities sold under agreements to repurchase	427,661	563,211
Total Fair Value [Member] \| Level 2 [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Available for sale securities	5,779,381	6,986,698
Held to maturity securities	2,615,798	1,631,482
Loans, net	4,806	13,253
Loans held for sale	44,253	93,069
Derivative financial instruments	78,793	75,867
FHLB short-term borrowings	200,000	1,119,026
Long-term debt	240,091	253,677
Derivative financial instruments	115,541	30,930
Total Fair Value [Member] \| Level 3 [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Loans, net	21,533,014	20,720,568
Deposits	29,830,503	30,432,646
Derivative financial instruments	3,111	4,116
Carrying Amount [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Cash, interest-bearing bank deposits, and federal funds sold	1,569,470	4,231,836
Available for sale securities	5,779,381	6,986,698
Held to maturity securities	2,752,012	1,565,751
Loans, net	21,537,893	20,792,217
Loans held for sale	44,253	93,069
Derivative financial instruments	78,793	75,867
Deposits	29,866,432	30,465,897
Federal funds purchased	2,350	1,850
Securities sold under agreements to repurchase	427,661	563,211
FHLB short-term borrowings	200,000	1,100,000
Long-term debt	240,091	244,220
Derivative financial instruments	$ 118,652	$ 35,046

Equity and debt available for sale securities.

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Fair value portion of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates.

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Fair value portion of deposit liabilities held by the entity, including, but not limited to, foreign and domestic, interest and noninterest bearing, demand deposits, saving deposits, negotiable orders of withdrawal (NOW) and time deposits.

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Fair value, after the effects of master netting arrangements, of a financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes assets not subject to a master netting arrangement and not elected to be offset.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Fair value portion of short term borrowing where a bank borrows, at the federal funds rate, from another bank.

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Fair value portion of borrowing from Federal Home Loan Bank (FHLBank).

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

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Amortized cost, after allowance for credit loss, of financing receivable. Excludes financing receivable covered under loss sharing agreement and net investment in lease.

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Fair value portion of securities that an entity sells and agrees to repurchase at a specified date for a specified price.

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