Fair Value - Estimated fair value and related carrying amount, of the Company's financial instruments (Details) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2022	Mar. 31, 2021	Dec. 31, 2021
Financial assets:
Trading securities	$ 74,234		$ 77,689
Financial liabilities:
Other derivative financial instruments (mortgage banking related)	(1,968)	$ (402,575)
Carrying Amount
Financial assets:
Cash and cash equivalents	6,032,606		6,843,147
Trading securities	74,234		77,689
Investment securities	8,931,233		7,173,947
Loans held for sale	130,376		191,723
Loans, net of allowance for credit losses	26,256,031		23,626,359
Accrued interest receivable	106,396		90,069
Mortgage servicing rights	83,339		65,620
Interest rate swap - non-designated hedge	408,434		408,776
Other derivative financial instruments (mortgage banking related)	4,381		5,966
Financial liabilities:
Deposits	38,775,830		35,054,829
Federal funds purchased and securities sold under agreements to repurchase	770,409		781,239
Other borrowings	405,553		327,066
Accrued interest payable	6,644		3,345
Interest rate swap - non-designated hedge	409,084		410,137
Other derivative financial instruments (mortgage banking related)	3,084
Fair Value
Financial assets:
Cash and cash equivalents	6,032,606		6,843,147
Trading securities	74,234		77,689
Investment securities	8,733,959		7,132,110
Loans held for sale	130,376		191,723
Loans, net of allowance for credit losses	26,434,330		23,921,372
Accrued interest receivable	106,396		90,069
Mortgage servicing rights	83,339		65,620
Interest rate swap - non-designated hedge	408,434		408,776
Other derivative financial instruments (mortgage banking related)	4,381		5,966
Financial liabilities:
Deposits	38,737,371		35,050,516
Federal funds purchased and securities sold under agreements to repurchase	770,409		781,239
Other borrowings	399,125		334,640
Accrued interest payable	6,644		3,345
Interest rate swap - non-designated hedge	409,084		410,137
Other derivative financial instruments (mortgage banking related)	3,084
Commitments to extend credit \| Fair Value
Financial liabilities:
Commitments to extend credit	63,247		93,501
Quoted Prices In Active Markets for Identical Assets (Level 1)
Financial assets:
Cash and cash equivalents	6,032,606		6,843,147
Investment securities	179,258		160,568
Significant Other Observable Inputs (Level 2)
Financial assets:
Trading securities	74,234		77,689
Investment securities	8,554,701		6,971,542
Loans held for sale	130,376		191,723
Accrued interest receivable	25,425		19,241
Interest rate swap - non-designated hedge	408,434		408,776
Other derivative financial instruments (mortgage banking related)	4,381		5,966
Financial liabilities:
Deposits	38,737,371		35,050,516
Federal funds purchased and securities sold under agreements to repurchase	770,409		781,239
Other borrowings	399,125		334,640
Accrued interest payable	6,644		3,345
Interest rate swap - non-designated hedge	409,084		410,137
Other derivative financial instruments (mortgage banking related)	3,084
Significant Other Observable Inputs (Level 2) \| Commitments to extend credit
Financial liabilities:
Commitments to extend credit	63,247		93,501
Significant Unobservable Inputs (Level 3)
Financial assets:
Loans, net of allowance for credit losses	26,434,330		23,921,372
Accrued interest receivable	80,971		70,828
Mortgage servicing rights	$ 83,339		$ 65,620

Fair value of accrued interest payable as on date.

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Fair value of accrued interest receivable as on date.

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Fair value portion of arrangements to extend credit.

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The element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, the element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. The item represents residential mortgage servicing rights as presented on the statement of financial position which are due to the entity as of the balance sheet date.

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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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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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Amount after offset of short term borrowing where a bank borrows, at the federal funds rate, from another bank and securities that an entity sells and agrees to repurchase at a specified date for a specified price.

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The increase (decrease) during the period in the carrying value of derivative instruments reported as liabilities that are due to be disposed of within one year (or the normal operating cycle, if longer).

+ References

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Fair value as of the balance sheet date of all derivative assets not designated as hedging instruments.

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Fair value as of the balance sheet date of all derivative liabilities not designated as hedging instruments.

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Fair value portion of investment securities, including, but not limited to, marketable securities, derivative financial instruments, and investments accounted for under the equity method.

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-Publisher FASB
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Fair value portion of loans held-for-sale including, but not limited to, mortgage loans and finance receivables.

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Fair value portion of loan receivable, including, but not limited to, mortgage loans held for investment, finance receivables held for investment, policy loans on insurance contracts.

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The carrying amount as of the balance sheet date for the aggregate of other miscellaneous borrowings owed by the reporting entity.

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- Definition

Amount of investment in debt security measured at fair value with change in fair value recognized in net income (trading).

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