Disclosures about Fair Value of Financial Instruments - Estimated Fair Values of Financial Instruments (Detail) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Assets:
Cash and cash equivalents, carrying value	$ 693,354	$ 212,505
Cash and cash equivalents, fair value	693,354	212,505
Debt securities, available for sale	1,206,431	577,198
Interest-only GNMA securities		16,272
Equity securities	3,854	2,406
Loans held for sale	79,086	486,328
Total loans and leases receivable, net of allowance for credit losses on loans and leases, carrying value	15,608,989	9,508,367
Total loans and leases receivable, net of allowance for credit losses on loans and leases, fair value	16,222,202	9,853,037
FHLB, Federal Reserve Bank and other restricted stock, carrying value	71,368	84,214
FHLB, Federal Reserve Bank and other restricted stock, fair value	71,368	84,214
Derivatives	54,223	23,608
Liabilities:
Deposits, carrying value	11,309,929	8,648,936	$ 7,142,236
Deposits, fair value	11,312,494	8,652,340
FRB PPP Liquidity facility, carrying value	4,415,016	0
FRB PPP Liquidity Facility, fair value	4,415,016
Federal funds purchased, carrying value	250,000	538,000
Federal funds purchased, fair value	250,000	538,000
FHLB advances, carrying value	850,000	850,000
FHLB advances, fair value	852,442	852,162
Other borrowings, carrying value	124,037	123,630
Other borrowings, fair value	129,120	127,603
Subordinated debt, carrying value	181,394	181,115
Subordinated debt, fair value	193,119	192,217
Derivatives	98,164	45,939
Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Cash and cash equivalents, fair value	693,354	212,505
Debt securities, available for sale	0	0
Interest-only GNMA securities		0
Equity securities	3,854	2,406
Loans held for sale	0	0
Total loans and leases receivable, net of allowance for credit losses on loans and leases, fair value	0	0
FHLB, Federal Reserve Bank and other restricted stock, fair value	0	0
Derivatives	0	0
Liabilities:
Deposits, fair value	10,657,998	6,980,402
FRB PPP Liquidity Facility, fair value	0
Federal funds purchased, fair value	250,000	538,000
FHLB advances, fair value	0	0
Other borrowings, fair value	0	0
Subordinated debt, fair value	0	0
Derivatives	0	0
Significant Other Observable Inputs (Level 2)
Assets:
Cash and cash equivalents, fair value	0	0
Debt securities, available for sale	1,206,431	577,198
Interest-only GNMA securities		0
Equity securities	0	0
Loans held for sale	78,443	2,130
Total loans and leases receivable, net of allowance for credit losses on loans and leases, fair value	3,616,432	2,245,758
FHLB, Federal Reserve Bank and other restricted stock, fair value	71,368	84,214
Derivatives	54,023	23,529
Liabilities:
Deposits, fair value	654,496	1,671,938
FRB PPP Liquidity Facility, fair value	4,415,016
Federal funds purchased, fair value	0	0
FHLB advances, fair value	852,442	852,162
Other borrowings, fair value	129,120	127,603
Subordinated debt, fair value	193,119	192,217
Derivatives	98,164	45,939
Significant Unobservable Inputs (Level 3)
Assets:
Cash and cash equivalents, fair value	0	0
Debt securities, available for sale	0	0
Interest-only GNMA securities		16,272
Equity securities	0	0
Loans held for sale	643	484,198
Total loans and leases receivable, net of allowance for credit losses on loans and leases, fair value	12,605,770	7,607,279
FHLB, Federal Reserve Bank and other restricted stock, fair value	0	0
Derivatives	200	79
Liabilities:
Deposits, fair value	0	0
FRB PPP Liquidity Facility, fair value	0
Federal funds purchased, fair value	0	0
FHLB advances, fair value	0	0
Other borrowings, fair value	0	0
Subordinated debt, fair value	0	0
Derivatives	$ 0	$ 0

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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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Amount 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. Excludes cash and cash equivalents within disposal group and discontinued operation.

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The aggregate of all deposit liabilities held by the entity, including foreign and domestic, interest and noninterest bearing; may include demand deposits, saving deposits, Negotiable Order of Withdrawal (NOW) and time deposits among others.

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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 of investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI).

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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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Amount of short term borrowing where a bank borrows, at the federal funds rate, from another bank.

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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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