Fair Value Disclosures (Details 3) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investment securities	$ 204,177	$ 214,257
Loans held for sale	774,100	2,571,300
Subordinated notes	282,219	282,129
Level 1 \| Carrying Amount
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investment securities	17,368	18,484
Level 1 \| Estimated Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investment securities	9,660,575	4,425,583
Investment securities	17,368	18,484
Level 2 \| Carrying Amount
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investment securities	11,927	12,396
Loans held for sale	767,370	2,570,091
Derivative assets		48,684
Federal funds purchased	289,165	132,270
Customer repurchase agreements	6,102	9,496
Other borrowings	4,900,000	2,400,000
Subordinated notes	282,219	282,129
Trust preferred subordinated debentures	113,406	113,406
Derivative liabilities		51,310
Level 2 \| Estimated Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investment securities	11,927	12,396
Loans held for sale	767,370	2,570,091
Derivative assets	125,913	48,684
Federal funds purchased	289,165	132,270
Customer repurchase agreements	6,102	9,496
Other borrowings	4,900,000	2,400,000
Subordinated notes	281,793	292,302
Trust preferred subordinated debentures	113,406	113,406
Derivative liabilities	126,459	51,310
Level 3 \| Carrying Amount
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investment securities	199,489	208,991
Loans held for sale	6,694	7,043
Loans held for investment, net	24,205,424	24,451,215
Deposits	27,134,263	26,478,593
Level 3 \| Estimated Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investment securities	199,489	208,991
Loans held for sale	6,694	7,043
Loans held for investment, net	24,170,104	24,478,586
Deposits	$ 30,302,466	$ 29,357,121

Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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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 of subordinated debt obligations including, but not limited to, subordinated loan, subordinated bond, subordinated debenture or junior debt.

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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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