Fair Value Measurements (Estimated Fair Values of Financial Instruments) (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Held to maturity securities	$ 1,565,751	$ 1,357,170
Loans held-for-sale, fair value	41,022	0
Derivative financial instruments	6,908	2,869
Derivative financial instruments	22,244	44,841
Total Fair Value [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Cash, interest-bearing bank deposits, and federal funds sold	4,231,836	1,860,092
Available for sale securities	6,986,698	5,999,327
Held to maturity securities	1,631,482	1,467,581
Loans, net	20,733,821	21,533,384
Loans held-for-sale, fair value	93,069	136,063
Derivative financial instruments	75,867	150,180
Deposits	30,432,646	27,679,321
Federal funds purchased	1,850	300
Securities sold under agreements to repurchase	563,211	567,213
Short-term FHLB Borrowings	1,119,026	1,147,335
Long-term debt	253,677	404,880
Derivative financial instruments	35,046	55,257
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	4,231,836	1,860,092
Federal funds purchased	1,850	300
Securities sold under agreements to repurchase	563,211	567,213
Total Fair Value [Member] \| Level 2 [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Available for sale securities	6,986,698	5,999,327
Held to maturity securities	1,631,482	1,467,581
Loans, net	13,253	60,451
Loans held-for-sale, fair value	93,069	136,063
Derivative financial instruments	75,867	150,180
Short-term FHLB Borrowings	1,119,026	1,147,335
Long-term debt	253,677	404,880
Derivative financial instruments	30,930	49,612
Total Fair Value [Member] \| Level 2 [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Loans, net	20,720,568	21,472,933
Deposits	30,432,646	27,679,321
Derivative financial instruments	4,116	5,645
Carrying Amount [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Cash, interest-bearing bank deposits, and federal funds sold	4,231,836	1,860,092
Available for sale securities	6,986,698	5,999,327
Held to maturity securities	1,565,751	1,357,170
Loans, net	20,792,217	21,339,754
Loans held-for-sale, fair value	93,069	136,063
Derivative financial instruments	75,867	150,180
Deposits	30,465,897	27,697,877
Federal funds purchased	1,850	300
Securities sold under agreements to repurchase	563,211	567,213
Short-term FHLB Borrowings	1,100,000	1,100,000
Long-term debt	244,220	378,322
Derivative financial instruments	$ 35,046	$ 55,257

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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Amount, after allowance for credit loss, of financing receivable. Excludes financing receivable covered under loss sharing agreement.

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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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