FAIR VALUES OF FINANCIAL INSTRUMENTS - Carrying Amounts and Estimated Fair Values of Financial Instruments (Detail) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Financial assets
Cash and cash equivalents	$ 346,704	$ 387,699
Securities available-for-sale	2,424,593	2,575,469
Federal Home Loan Bank and other bank stock	82,715	75,654
Loans held-for-sale	50,138	105,806
Loans and leases receivable, net of ALLL	6,838,745	6,601,767
Accrued interest receivable	36,941	35,355
Derivative assets	1,159	1,005
Financial liabilities
Deposits	6,848,132	7,063,613
Advances from Federal Home Loan Bank	1,901,137	1,695,039
Long term debt	179,310	180,560
Derivative liabilities	1,136	1,033
Accrued interest payable	9,173	7,321
Discontinued Operations, Disposed of by Sale \| Banc Home Loan
Financial liabilities
Loans held-for-sale, carried at fair value	29,888	38,696
Quoted Prices in Active Markets for Identical Assets (Level 1)
Financial assets
Cash and cash equivalents	346,704	387,699
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	36,941	35,355
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	9,173	7,321
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	2,424,593	2,575,469
Federal Home Loan Bank and other bank stock	82,715	75,654
Loans held-for-sale	7,176	6,866
Loans and leases receivable, net of ALLL	0	0
Accrued interest receivable	0	0
Derivative assets	1,159	1,005
Financial liabilities
Deposits	0	0
Advances from Federal Home Loan Bank	1,901,137	1,695,039
Long term debt	179,310	180,560
Derivative liabilities	1,136	1,033
Accrued interest payable	0	0
Significant Other Observable Inputs (Level 2) \| Recurring
Financial assets
Loans held-for-sale	5,872	6,359
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	5,900	6,400
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	42,962	98,940
Loans and leases receivable, net of ALLL	6,838,745	6,601,767
Accrued interest receivable	0	0
Derivative assets	0	0
Financial liabilities
Deposits	6,848,132	7,063,613
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	42,962	98,940
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	24,000	32,300
Carrying Value
Financial assets
Cash and cash equivalents	346,704	387,699
Securities available-for-sale	2,424,593	2,575,469
Federal Home Loan Bank and other bank stock	82,715	75,654
Loans held-for-sale	50,068	105,765
Loans and leases receivable, net of ALLL	6,875,744	6,610,074
Accrued interest receivable	36,941	35,355
Derivative assets	1,159	1,005
Financial liabilities
Deposits	7,110,165	7,292,903
Advances from Federal Home Loan Bank	1,905,000	1,695,000
Long term debt	172,966	172,941
Derivative liabilities	1,136	1,033
Accrued interest payable	9,173	7,321
Carrying Value \| Recurring
Financial assets
Loans held-for-sale	$ 48,834	$ 105,299

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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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 debt securities categorized neither as held-to-maturity nor trading.

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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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No definition available.

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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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