Fair Value - Estimated fair value and related carrying amount, of the Company's financial instruments (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Jul. 07, 2020	Dec. 31, 2019
Financial assets:
Trading securities		$ 10,674
Financial liabilities:
Other borrowings	$ 390,179		$ 700,103
Other derivative financial instruments (Mortgage banking related)	804,832		31,273
Carrying Amount
Financial assets:
Cash and cash equivalents	4,609,255		688,704
Trading securities	10,674
Investment securities	4,446,657		2,005,171
Loans held for sale	290,467		59,363
Loans, net of allowance for loan losses	24,206,825		11,313,113
Accrued interest receivable	107,601		36,774
Mortgage servicing rights	43,820		30,525
Interest rate swap - non-designated hedge	802,763		15,350
Other derivative financial instruments (mortgage banking related)	11,136		902
Financial liabilities:
Deposits	30,693,882		12,177,096
Federal funds purchased and securities sold under agreements to repurchase	779,666		298,741
Other borrowings	390,179		815,936
Accrued interest payable	7,103		4,916
Interest rate swap - non-designated hedge	804,832		16,693
Interest rate swap - cash flow hedge			13,791
Other derivative financial instruments (Mortgage banking related)			789
Fair Value
Financial assets:
Cash and cash equivalents	4,609,255		688,704
Trading securities	10,674
Investment securities	4,448,300		2,005,171
Loans held for sale	290,467		59,363
Loans, net of allowance for loan losses	24,757,859		11,452,003
Accrued interest receivable	107,601		36,774
Mortgage servicing rights	43,820		30,525
Interest rate swap - non-designated hedge	802,763		15,350
Other derivative financial instruments (mortgage banking related)	11,136		902
Financial liabilities:
Deposits	30,719,416		11,406,477
Federal funds purchased and securities sold under agreements to repurchase	779,666		298,741
Other borrowings	386,126		818,210
Accrued interest payable	7,103		4,916
Interest rate swap - non-designated hedge	804,832		16,693
Interest rate swap - cash flow hedge			13,791
Other derivative financial instruments (Mortgage banking related)			789
Commitments to extend credit \| Fair Value
Financial liabilities:
Commitments to extend credit	136,726		36,031
Quoted Prices In Active Markets for Identical Assets (Level 1)
Financial assets:
Cash and cash equivalents	4,609,255		688,704
Investment securities	160,443		49,124
Significant Other Observable Inputs (Level 2)
Financial assets:
Trading securities	10,674
Investment securities	4,287,857		1,956,047
Loans held for sale	290,467		59,363
Accrued interest receivable	12,952		8,500
Interest rate swap - non-designated hedge	802,763		15,350
Other derivative financial instruments (mortgage banking related)	11,136		902
Financial liabilities:
Deposits	30,719,416		11,406,477
Federal funds purchased and securities sold under agreements to repurchase	779,666		298,741
Other borrowings	386,126		818,210
Accrued interest payable	7,103		4,916
Interest rate swap - non-designated hedge	804,832		16,693
Interest rate swap - cash flow hedge			13,791
Other derivative financial instruments (Mortgage banking related)			789
Significant Other Observable Inputs (Level 2) \| Commitments to extend credit
Financial liabilities:
Commitments to extend credit	136,726		36,031
Significant Unobservable Inputs (Level 3)
Financial assets:
Loans, net of allowance for loan losses	24,757,859		11,452,003
Accrued interest receivable	94,649		28,274
Mortgage servicing rights	$ 43,820		$ 30,525

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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Fair value, after the effects of master netting arrangements, of a financial liability or 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 liabilities not subject to a master netting arrangement and not elected to be offset.

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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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Fair value as of the balance sheet date of all interest rate derivative liabilities designated as cash flow hedging instruments.

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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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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 fair value amount of long-term debt whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this 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.

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

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