FAIR VALUES OF FINANCIAL INSTRUMENTS - Carrying Amounts and Estimated Fair Values of Financial Instruments (Detail) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Financial assets
Cash and cash equivalents	$ 304,705	$ 391,592
Securities available-for-sale	1,471,303	1,992,500
Federal Home Loan Bank and other bank stock	55,794	68,094
Loans held-for-sale	25,191	27,606
Loans and leases receivable, net of ALLL	7,360,071	7,513,910
Accrued interest receivable	36,468	38,807
Derivative assets	2,366	1,534
Financial liabilities
Deposits	7,536,887	7,689,324
Advances from Federal Home Loan Bank	938,536	1,517,761
Long term debt	173,483	174,059
Derivative liabilities	2,529	1,600
Accrued interest payable	16,726	13,253
Discontinued Operations, Disposed of by Sale \| Banc Home Loan
Financial liabilities
Loans held-for-sale, carried at fair value	0	19,500
Quoted Prices in Active Markets for Identical Assets (Level 1)
Financial assets
Cash and cash equivalents	304,705	391,592
Securities available-for-sale	0	0
Federal Home Loan Bank and other bank stock	0	0
Loans held-for-sale	0	0
Loans and leases receivable, net of ALLL	0	0
Accrued interest receivable	36,468	38,807
Derivative assets	0	0
Financial liabilities
Deposits	0	0
Advances from Federal Home Loan Bank	0	0
Long term debt	0	0
Derivative liabilities	0	0
Accrued interest payable	16,726	13,253
Quoted Prices in Active Markets for Identical Assets (Level 1) \| Recurring
Financial assets
Loans held-for-sale	0	0
Significant Other Observable Inputs (Level 2)
Financial assets
Cash and cash equivalents	0	0
Securities available-for-sale	1,471,303	1,992,500
Federal Home Loan Bank and other bank stock	55,794	68,094
Loans held-for-sale	2,122	2,566
Loans and leases receivable, net of ALLL	0	0
Accrued interest receivable	0	0
Derivative assets	2,366	1,534
Financial liabilities
Deposits	0	0
Advances from Federal Home Loan Bank	938,536	1,517,761
Long term debt	173,483	174,059
Derivative liabilities	2,529	1,600
Accrued interest payable	0	0
Significant Other Observable Inputs (Level 2) \| Recurring
Financial assets
Loans held-for-sale	2,122	2,140
Significant Other Observable Inputs (Level 2) \| Recurring \| Discontinued Operations, Disposed of by Sale \| Banc Home Loan
Financial liabilities
Loans held-for-sale, carried at fair value	0	2,100
Significant Unobservable Inputs (Level 3)
Financial assets
Cash and cash equivalents	0	0
Securities available-for-sale	0	0
Federal Home Loan Bank and other bank stock	0	0
Loans held-for-sale	23,069	25,040
Loans and leases receivable, net of ALLL	7,360,071	7,513,910
Accrued interest receivable	0	0
Derivative assets	0	0
Financial liabilities
Deposits	7,536,887	7,689,324
Advances from Federal Home Loan Bank	0	0
Long term debt	0	0
Derivative liabilities	0	0
Accrued interest payable	0	0
Significant Unobservable Inputs (Level 3) \| Recurring
Financial assets
Loans held-for-sale	23,069	25,040
Significant Unobservable Inputs (Level 3) \| Recurring \| Discontinued Operations, Disposed of by Sale \| Banc Home Loan
Financial liabilities
Loans held-for-sale, carried at fair value	0	17,400
Carrying Value
Financial assets
Cash and cash equivalents	304,705	391,592
Securities available-for-sale	1,471,303	1,992,500
Federal Home Loan Bank and other bank stock	55,794	68,094
Loans held-for-sale	25,191	27,606
Loans and leases receivable, net of ALLL	7,493,315	7,638,681
Accrued interest receivable	36,468	38,807
Derivative assets	2,366	1,534
Financial liabilities
Deposits	7,724,932	7,916,644
Advances from Federal Home Loan Bank	935,000	1,520,000
Long term debt	173,203	173,174
Derivative liabilities	2,529	1,600
Accrued interest payable	16,726	13,253
Carrying Value \| Recurring
Financial assets
Loans held-for-sale	$ 25,191	$ 27,180

Disposal Group, Including Discontinued Operation, Loans Receivable Held-For-Sale, Net

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Investment in Federal Home Loan and Other Banks Stock, Fair Value Disclosure

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Loans Held-for-sale, Fair Value Disclosure and Disposal Group, Including Discontinued Operation, Loans Held-for-sale, Fair Value Disclosure

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Fair value portion of amount due from customers or clients for goods or services, including trade receivables, that have been delivered or sold in the normal course of business, and amounts due from others, including related parties.

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Fair value portion of accrued expenses.

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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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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 borrowing from Federal Home Loan Bank (FHLBank).

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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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