Fair Value Measurements - Fair Value on Balance Sheet (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Financial assets:
Debt securities available for sale, at fair value	$ 1,245,300	$ 1,098,336
Debt securities held to maturity	288,439	289,505
Equity securities	4,706	2,855
Quoted Prices in Active Markets for Identical Assets (Level 1)
Financial assets:
Cash and cash equivalents	265,896	75,547
Debt securities available for sale, at fair value	30,668	42,386
Debt securities held to maturity	5,004	19,960
Equity securities	4,379	2,587
Federal Home Loan Bank stock	0	0
Loans receivable, net	0	0
Derivative assets		0
Financial liabilities:
Deposits	0	0
Borrowings	0	0
Derivative liabilities	0	0
Significant Other Observable Inputs (Level 2)
Financial assets:
Cash and cash equivalents	0	0
Debt securities available for sale, at fair value	1,214,632	1,055,950
Debt securities held to maturity	283,435	269,545
Equity securities	327	268
Federal Home Loan Bank stock	53,416	69,579
Loans receivable, net	0	0
Derivative assets		185
Financial liabilities:
Deposits	6,649,238	5,654,075
Borrowings	1,027,590	1,411,962
Derivative liabilities	47,873	11,546
Significant Unobservable Inputs (Level 3)
Financial assets:
Cash and cash equivalents	0	0
Debt securities available for sale, at fair value	0	0
Debt securities held to maturity	0	0
Equity securities	0	0
Federal Home Loan Bank stock	0	0
Loans receivable, net	6,657,586	6,219,008
Derivative assets		0
Financial liabilities:
Deposits	0	0
Borrowings	0	0
Derivative liabilities	0	0
Carrying Value
Financial assets:
Cash and cash equivalents	265,896	75,547
Debt securities available for sale, at fair value	1,245,300	1,098,336
Debt securities held to maturity	272,712	285,756
Equity securities	4,706	2,855
Federal Home Loan Bank stock	53,416	69,579
Loans receivable, net	6,392,712	6,135,857
Derivative assets	22,305	185
Financial liabilities:
Deposits	6,629,648	5,645,842
Borrowings	1,015,210	1,407,022
Derivative liabilities	47,873	11,546
Total Fair Value
Financial assets:
Cash and cash equivalents	265,896	75,547
Debt securities available for sale, at fair value	1,245,300	1,098,336
Debt securities held to maturity	288,439	289,505
Equity securities	4,706	2,855
Federal Home Loan Bank stock	53,416	69,579
Loans receivable, net	6,657,586	6,219,008
Derivative assets		185
Financial liabilities:
Deposits	6,649,238	5,654,075
Borrowings	1,027,590	1,411,962
Derivative liabilities	$ 47,873	$ 11,546

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 debt instrument payable, including, but not limited to, notes payable and loans payable.

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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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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 investment in debt security measured at amortized cost (held-to-maturity).

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Fair value portion of investments in Federal Home Loan Bank (FHLBank) stock.

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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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