Financial Instruments with Off-Balance Sheet Risk and Derivative Transactions - Fair Value of Derivatives (Details)	1 Months Ended	12 Months Ended
Dec. 31, 2019 USD ($) item	Dec. 31, 2019 USD ($) item	Dec. 31, 2018 USD ($) item
Financial Instruments with Off-Balance Sheet Risk and Derivative Transactions
Loan pool hedge	$ 50,000,000	$ 50,000,000
Term of interest rate risk cash flow hedge	5 years
Designated as Hedging Instrument [Member]
Financial Instruments with Off-Balance Sheet Risk and Derivative Transactions
Derivative liabilities designated as hedging instruments, fair value	$ 3,150,000	$ 3,150,000	$ 58,000
Designated as Hedging Instrument [Member] \| Interest Rate Products \| OSBC Affiliates
Financial Instruments with Off-Balance Sheet Risk and Derivative Transactions
Derivative, number of transactions \| item	2	2	1
Notional Amount	$ 75,774,000	$ 75,774,000	$ 25,774,000
Derivative liabilities designated as hedging instruments, fair value	3,150,000	3,150,000	58,000
Not Designated as Hedging Instrument [Member]
Financial Instruments with Off-Balance Sheet Risk and Derivative Transactions
Derivative assets designated as hedging instruments, fair value	3,170,000	3,170,000	831,000
Derivative liabilities designated as hedging instruments, fair value	$ 2,973,000	$ 2,973,000	$ 698,000
Not Designated as Hedging Instrument [Member] \| Interest Rate Products \| Commercial Loan Customers
Financial Instruments with Off-Balance Sheet Risk and Derivative Transactions
Derivative, number of transactions \| item	25	25	25
Notional Amount	$ 177,872,000	$ 177,872,000	$ 188,931,000
Derivative assets designated as hedging instruments, fair value	2,920,000	2,920,000	672,000
Derivative liabilities designated as hedging instruments, fair value	2,920,000	$ 2,920,000	$ 672,000
Weighted average maturity		5 years 10 months 24 days	6 years 7 months 6 days
Not Designated as Hedging Instrument [Member] \| Interest Rate Swap [Member]
Financial Instruments with Off-Balance Sheet Risk and Derivative Transactions
Cash collateral pledged with financial institutions, dollars	114,000	$ 114,000	$ 260,000
Investment securities pledged with financial institutions, dollars	$ 11,000,000	$ 11,000,000	$ 0
Number of correspondent financial institutions where investment securities are pledged		1	1
Number of financial institutions where investment securities are required to be pledged \| item		2
Not Designated as Hedging Instrument [Member] \| Interest Rate Lock Commitments and Forward Contracts
Financial Instruments with Off-Balance Sheet Risk and Derivative Transactions
Derivative, number of transactions \| item	87	87	63
Notional Amount	$ 23,667,000	$ 23,667,000	$ 18,130,000
Derivative assets designated as hedging instruments, fair value	$ 250,000	$ 250,000	$ 159,000
Not Designated as Hedging Instrument [Member] \| Other Contracts
Financial Instruments with Off-Balance Sheet Risk and Derivative Transactions
Derivative, number of transactions \| item	4	4	3
Notional Amount	$ 28,176,000	$ 28,176,000	$ 18,155,000
Derivative liabilities designated as hedging instruments, fair value	53,000	53,000	26,000
Not Designated as Hedging Instrument [Member] \| Forward Contracts [Member]
Financial Instruments with Off-Balance Sheet Risk and Derivative Transactions
Notional Amount	13,500,000	13,500,000	$ 9,315,000
Interest Income [Member]
Financial Instruments with Off-Balance Sheet Risk and Derivative Transactions
Amount to be reclassified as a reduction to interest expense during the next twelve months	17,000	17,000
Interest Expense [Member]
Financial Instruments with Off-Balance Sheet Risk and Derivative Transactions
Amount to be reclassified as a reduction to interest expense during the next twelve months	$ 274,000	$ 274,000

Carrying amount as of the balance sheet date of loan pool hedge for securities.

No definition available.

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- Definition

Represents the number of financial institutions where investment securities are pledged.

+ References

No definition available.

+ Details

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- Definition

Number of financial institutions where investment securities are required to be pledged.

+ References

No definition available.

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- Definition

Carrying amount as of the balance sheet date of cash collateral held for borrowed securities, for which the cash is restricted as to withdrawal or usage.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03.1)
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
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-Subparagraph (SX 210.7-03.(a),2)
-URI http://asc.fasb.org/extlink&oid=119400593&loc=d3e572229-122910

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- Definition

Fair value of all asset derivatives designated as cash flow hedging instruments.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4B
-Subparagraph (c)(1)
-URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5624163-113959

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- Definition

Fair value of all liability derivatives designated as cash flow hedging instruments.

+ References

+ Details

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- Definition

Average remaining period until maturity of the derivative contract, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

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- Definition

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.

+ References

No definition available.

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- Definition

Nominal or face amount used to calculate payment on derivative.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 1B
-URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5580258-113959

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 1A
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5579245-113959

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Balance Type:	na
Period Type:	instant

- Definition

The number of derivative instruments of a particular group held by the entity.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 1A
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-URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5579245-113959

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-Section 50
-Paragraph 1B
-URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5580258-113959

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- Definition

The estimated net amount of unrealized gains or losses on interest rate cash flow hedges as of the balance sheet date expected to be reclassified to earnings within the next twelve months.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 30
-Section 50
-Paragraph 1
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=112277219&loc=d3e80748-113994

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- Definition

Maximum period the entity is hedging its exposure to the variability in future cash flows for forecasted transactions, excluding those forecasted transactions related to the payment of variable interest on existing financial instruments, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 30
-Section 50
-Paragraph 1
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-URI http://asc.fasb.org/extlink&oid=112277219&loc=d3e80748-113994

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- Definition

The carrying amount as of the date of the latest financial statement presented of securities which are owned but transferred to serve as collateral for debt facilities other than FHLB loans, repurchase agreements and letter of credit arrangements, and for which the transferee does not have the right by contract or custom to sell or re-pledge them to an unrelated party.

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 30
-Section 50
-Paragraph 1A
-Subparagraph (b)(1)(i)
-URI http://asc.fasb.org/extlink&oid=109249958&loc=SL6224234-111729

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