Fair Value - Estimated fair value and related carrying amount, of the Company's financial instruments (Details) - USD ($) $ in Thousands	6 Months Ended
Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Financial assets:
Trading securities	$ 494
Loans held for sale	603,275	$ 47,796	$ 59,363
Interest Receivable	94,500
Financial liabilities:
Increase (Decrease) in Loans Held-for-sale	1,045,044	214,785
Other borrowings	700,099	700,914	700,103
Other derivative financial instruments (Mortgage banking related)	1,017,933	30,286	30,485
Carrying Amount
Financial assets:
Cash and cash equivalents	4,363,708	851,971	688,704
Trading securities	494
Investment securities	3,271,148	1,766,400	2,005,171
Loans held for sale	603,275		59,363
Loans held for sale		47,796
Loans, net of allowance for loan losses	25,064,539	11,167,979	11,313,113
Accrued interest receivable	106,938	38,650	36,774
Mortgage servicing rights	25,441	30,332	30,525
Interest rate swap - non-designated hedge	966,034	14,561	15,350
Other derivative financial instruments (mortgage banking related)	12,223	3,026	902
Financial liabilities:
Deposits	29,957,285	11,922,280	12,177,096
Federal Funds Purchased and Securities Sold under Agreements to Repurchase.	720,479		298,741
Federal funds purchased and securities sold under agreements to repurchase		298,029
Other borrowings	1,089,279		815,936
Other borrowings		816,414
Accrued interest payable	9,232	6,168	4,916
Interest rate swap - non-designated hedge	972,513	15,952	16,693
Interest rate swap - cash flow hedge	45,420	14,334	13,791
Other derivative financial instruments (Mortgage banking related)			789
Fair Value
Financial assets:
Cash and cash equivalents	4,363,708	851,971	688,704
Trading securities	494
Investment securities	3,271,148	1,766,400	2,005,171
Loans held for sale	603,275		59,363
Loans held for sale		47,796
Loans, net of allowance for loan losses	24,974,102	11,278,624	11,452,003
Accrued interest receivable	106,938	38,650	36,774
Mortgage servicing rights	25,441	30,332	30,525
Interest rate swap - non-designated hedge	966,034	14,561	15,350
Other derivative financial instruments (mortgage banking related)	12,223	3,026	902
Financial liabilities:
Deposits	29,976,226	11,124,796	11,406,477
Federal Funds Purchased and Securities Sold under Agreements to Repurchase.	720,479		298,741
Federal funds purchased and securities sold under agreements to repurchase		298,029
Other borrowings	1,071,443		818,210
Other borrowings		819,306
Accrued interest payable	9,232	6,168	4,916
Interest rate swap - non-designated hedge	972,513	15,952	16,693
Interest rate swap - cash flow hedge	45,420	14,334	13,791
Other derivative financial instruments (Mortgage banking related)			789
Commitments to extend credit		27,579
Commitments to extend credit \| Fair Value
Financial liabilities:
Commitments to extend credit	(21,456)		36,031
Quoted Prices In Active Markets for Identical Assets (Level 1)
Financial assets:
Cash and cash equivalents	4,363,708	851,971	688,704
Investment securities	133,430	49,124	49,124
Significant Other Observable Inputs (Level 2)
Financial assets:
Trading securities	494
Investment securities	3,137,718	1,717,276	1,956,047
Loans held for sale	603,275		59,363
Loans held for sale		47,796
Accrued interest receivable	11,228	7,880	8,500
Interest rate swap - non-designated hedge	966,034	14,561	15,350
Other derivative financial instruments (mortgage banking related)	12,223	3,026	902
Financial liabilities:
Deposits	29,976,226	11,124,796	11,406,477
Federal Funds Purchased and Securities Sold under Agreements to Repurchase.	720,479		298,741
Federal funds purchased and securities sold under agreements to repurchase		298,029
Other borrowings	1,071,443		818,210
Other borrowings		819,306
Accrued interest payable	9,232	6,168	4,916
Interest rate swap - non-designated hedge	972,513	15,952	16,693
Interest rate swap - cash flow hedge	45,420	14,334	13,791
Other derivative financial instruments (Mortgage banking related)			789
Commitments to extend credit		27,579
Significant Other Observable Inputs (Level 2) \| Commitments to extend credit
Financial liabilities:
Commitments to extend credit	(21,456)		36,031
Significant Unobservable Inputs (Level 3)
Financial assets:
Loans, net of allowance for loan losses	24,974,102	11,278,624	11,452,003
Accrued interest receivable	95,710	30,770	28,274
Mortgage servicing rights	$ 25,441	$ 30,332	$ 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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Fair value portion 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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No definition available.

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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 reporting period in the value of loans or securitized loans that are held with the intention to sell in the near future.

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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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Carrying amount as of the balance sheet date of interest earned but not received. Also called accrued interest or accrued interest receivable.

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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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Amount, after allowance for bad debt, of loan receivables held-for-sale that are not part of a disposal group. Excludes loans and leases covered under loss sharing agreements and loans classified as debt securities.

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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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