FAIR VALUES OF FINANCIAL INSTRUMENTS - Carrying Amounts and Estimated Fair Values of Financial Instruments (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Financial assets
Cash and cash equivalents	$ 220,819	$ 373,472
Securities available-for-sale	1,231,431	912,580
Federal Home Loan Bank and other bank stock	44,506	59,420
Loans held-for-sale	1,413	22,642
Loans receivable, net of allowance	5,936,708	5,894,732
Accrued interest receivable	29,445	24,523
Derivative assets	7,632	3,583
Financial liabilities
Deposits	6,087,714	5,430,536
Advances from Federal Home Loan Bank	585,416	1,222,709
Long-term debt	273,230	180,213
Derivative liabilities	8,102	3,853
Accrued interest payable	3,714	4,687
Quoted Prices in Active Markets for Identical Assets (Level 1)
Financial assets
Cash and cash equivalents	220,819	373,472
Securities available-for-sale	0	0
Federal Home Loan Bank and other bank stock	0	0
Loans held-for-sale	0	0
Loans receivable, net of allowance	0	0
Accrued interest receivable	29,445	24,523
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	3,714	4,687
Significant Other Observable Inputs (Level 2)
Financial assets
Cash and cash equivalents	0	0
Securities available-for-sale	1,231,431	912,580
Federal Home Loan Bank and other bank stock	44,506	59,420
Loans held-for-sale	468	3,409
Loans receivable, net of allowance	0	0
Accrued interest receivable	0	0
Derivative assets	7,632	3,583
Financial liabilities
Deposits	0	0
Advances from Federal Home Loan Bank	585,416	1,222,709
Long-term debt	273,230	180,213
Derivative liabilities	8,102	3,853
Accrued interest payable	0	0
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	945	19,233
Loans receivable, net of allowance	5,936,708	5,894,732
Accrued interest receivable	0	0
Derivative assets	0	0
Financial liabilities
Deposits	6,087,714	5,430,536
Advances from Federal Home Loan Bank	0	0
Long-term debt	0	0
Derivative liabilities	0	0
Accrued interest payable	0	0
Carrying Value
Financial assets
Cash and cash equivalents	220,819	373,472
Securities available-for-sale	1,231,431	912,580
Federal Home Loan Bank and other bank stock	44,506	59,420
Loans held-for-sale	1,413	22,642
Loans receivable, net of allowance	5,817,375	5,894,236
Accrued interest receivable	29,445	24,523
Derivative assets	7,632	3,583
Financial liabilities
Deposits	6,085,800	5,427,167
Advances from Federal Home Loan Bank	539,795	1,195,000
Long-term debt	256,315	173,421
Derivative liabilities	8,102	3,853
Accrued interest payable	$ 3,714	$ 4,687

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

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- Definition

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 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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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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