Disclosures about Fair Value of Financial Instruments - Estimated Fair Values of Financial Instruments (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents, carrying value	$ 62,135	$ 146,323	$ 264,709	$ 264,593
Cash and cash equivalents, fair value	62,135	146,323
Investment securities available for sale, fair value	665,012	471,371
Debt securities available for sale, at fair value	663,294
Debt securities, available for sale, fair value	663,294	471,371
Equity securities, carrying amount	1,718
Equity securities, at fair value	1,718
Loans held for sale, carrying value	1,507	146,077
Loans held for sale, fair value	1,507	146,251
Loans receivable, net of allowance for loan losses, carrying value	8,503,522	8,523,651
Loans receivable, net of allowance for loan losses, fair value	8,481,128	8,470,171
FHLB, Federal Reserve Bank and other restricted stock, carrying value	89,685	105,918
FHLB, Federal Reserve Bank and other restricted stock, fair value	89,685	105,918
Derivative assets, carrying value	14,693	9,752
Derivative assets, fair value	14,693	9,752
Deposits, carrying value	7,142,236	6,800,142
Deposits, fair value	7,136,009	6,796,095
Federal funds purchased, carrying value	187,000	155,000
Federal funds purchased, fair value	187,000	155,000
FHLB advances, carrying value	1,248,070	1,611,860
FHLB advances, fair value	1,248,046	1,611,603
Other borrowings, carrying value	123,871	186,497
Other borrowings, fair value	121,718	193,557
Subordinated debt, carrying value	108,977	108,880
Subordinated debt, fair value	110,550	115,775
Derivative liabilities, carrying value	16,286	10,074
Derivative liabilities, fair value	16,286	10,074
Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents, fair value	62,135	146,323
Debt securities, available for sale, fair value	0	3,352
Equity securities, at fair value	1,718
Loans held for sale, fair value	0	0
Loans receivable, net of allowance for loan losses, fair value	0	0
FHLB, Federal Reserve Bank and other restricted stock, fair value	0	0
Derivative assets, carrying value	0	0
Derivative assets, fair value	0	0
Deposits, fair value	5,408,055	4,894,449
Federal funds purchased, fair value	187,000	155,000
FHLB advances, fair value	998,070	881,860
Other borrowings, fair value	0	65,072
Subordinated debt, fair value	0	0
Derivative liabilities, carrying value	0	0
Derivative liabilities, fair value	0	0
Significant Other Observable Inputs (Level 2)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents, fair value	0	0
Debt securities, available for sale, fair value	663,294	468,019
Equity securities, at fair value	0
Loans held for sale, fair value	1,507	1,886
Loans receivable, net of allowance for loan losses, fair value	1,405,420	1,793,408
FHLB, Federal Reserve Bank and other restricted stock, fair value	89,685	105,918
Derivative assets, carrying value	14,624	9,692
Derivative assets, fair value	14,624	9,692
Deposits, fair value	1,727,954	1,901,646
Federal funds purchased, fair value	0	0
FHLB advances, fair value	249,976	729,743
Other borrowings, fair value	121,718	128,485
Subordinated debt, fair value	110,550	115,775
Derivative liabilities, carrying value	16,286	10,074
Derivative liabilities, fair value	16,286	10,074
Significant Unobservable Inputs (Level 3)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents, fair value	0	0
Debt securities, available for sale, fair value	0	0
Equity securities, at fair value	0
Loans held for sale, fair value	0	144,365
Loans receivable, net of allowance for loan losses, fair value	7,075,708	6,676,763
FHLB, Federal Reserve Bank and other restricted stock, fair value	0	0
Derivative assets, carrying value	69	60
Derivative assets, fair value	69	60
Deposits, fair value	0	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
Derivative liabilities, carrying value	0	0
Derivative liabilities, fair value	$ 0	$ 0

Borrowings Fair Value Disclosure

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Equity Securities

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Equity Securities, at Fair Value

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Federal Home Loan Bank, Advances, Branch of FHLB Bank, Amount of Advances, Fair Value Disclosure

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Federal Home Loan Bank Stock And Federal Reserve Bank Stock Fair Value

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Investment Securities, at Fair Value, including available-for-sale debt securities, and equity securities presented under ASU 2016-01.

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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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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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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 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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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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

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Amount of advances from the Federal Home Loan Bank (FHLB).

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Amount of Federal Home Loan Bank (FHLB) and Federal Reserve Bank stock.

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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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Amount after allowance and deduction of deferred interest and fees, unamortized costs and premiums over and discounts from face amounts, of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Includes loans and leases covered under loss sharing agreements.

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

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Fair value of all derivative liabilities not designated as a hedging instrument.

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Including the current and noncurrent portions, carrying value as of the balance sheet date of subordinated debt (with initial maturities beyond one year or beyond the operating cycle if longer). Subordinated debt places a lender in a lien position behind debt having a higher priority of repayment in liquidation of the entity's assets.

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