Derivatives, Hedging Activities and Financial Instruments with Off-Balance Sheet Risk - Fair Value of Derivatives (Details)	1 Months Ended	3 Months Ended	12 Months Ended
Dec. 31, 2019 USD ($) item	Mar. 31, 2020 USD ($) item	Dec. 31, 2019 USD ($) item
Derivatives, Hedging Activities and Financial Instruments with Off-Balance Sheet Risk
Loan pool hedge	$ 50,000,000		$ 50,000,000
Term of interest rate risk cash flow hedge	5 years
Derivative assets designated as hedging instruments, fair value		$ 2,838,000
Weighted average maturity			5 years 10 months 24 days
Designated as Hedging Instrument [Member]
Derivatives, Hedging Activities and Financial Instruments with Off-Balance Sheet Risk
Derivative liabilities designated as hedging instruments, fair value		$ 8,518,000
Designated as Hedging Instrument [Member] \| Interest Rate Products
Derivatives, Hedging Activities and Financial Instruments with Off-Balance Sheet Risk
Derivative, number of transactions \| item	2	2	2
Notional Amount	$ 75,774,000	$ 75,774,000	$ 75,774,000
Derivative assets designated as hedging instruments, classified in other assets		2,838,000
Derivated liabilities designated as hedging instruments, classified in other liabilities	3,150,000	8,518,000	3,150,000
Derivative liabilities designated as hedging instruments, fair value	3,150,000		3,150,000
Designated as Hedging Instrument [Member] \| Interest Rate Products \| OSBC Affiliates
Derivatives, Hedging Activities and Financial Instruments with Off-Balance Sheet Risk
Notional Amount	25,800,000		25,800,000
Not Designated as Hedging Instrument [Member]
Derivatives, Hedging Activities and Financial Instruments with Off-Balance Sheet Risk
Derivative assets not designated as hedging instruments, fair value		9,009,000
Total Derivative liabilities not designated as hedging instruments, fair value		$ 8,395,000
Not Designated as Hedging Instrument [Member] \| Interest Rate Products
Derivatives, Hedging Activities and Financial Instruments with Off-Balance Sheet Risk
Investment securities pledged with financial institutions, dollars	$ 11,000,000		$ 11,000,000
Not Designated as Hedging Instrument [Member] \| Interest Rate Products \| Commercial Loan Customers
Derivatives, Hedging Activities and Financial Instruments with Off-Balance Sheet Risk
Derivative, number of transactions \| item	25	350	25
Notional Amount	$ 177,872,000	$ 193,418,000	$ 177,872,000
Interest rate derivatives, derivative assets not designated as hedging instruments, classified in other assets	2,771,000	8,277,000	2,771,000
Interest rate derivatives, derivative not designated as hedging instruments, classified in other liabilities	2,771,000	$ 8,277,000	$ 2,771,000
Weighted average maturity		6 years	5 years 10 months 24 days
Not Designated as Hedging Instrument [Member] \| Interest Rate Swap [Member]
Derivatives, Hedging Activities and Financial Instruments with Off-Balance Sheet Risk
Cash collateral pledged with financial institutions, dollars	$ 114,000	$ 2,000,000	$ 114,000
Investment securities pledged with financial institutions, dollars		$ 14,600,000
Number of correspondent financial institutions where investment securities are pledged \| item		1	1
Number of financial institutions where investment securities are required to be pledged \| item		1	2
Not Designated as Hedging Instrument [Member] \| Interest Rate Lock Commitments and Forward Contracts
Derivatives, Hedging Activities and Financial Instruments with Off-Balance Sheet Risk
Derivative, number of transactions \| item	4	46	4
Notional Amount	$ 28,176,000	$ 80,500,000	$ 28,176,000
Interest rate derivatives, derivative assets not designated as hedging instruments, classified in other assets		$ 732,000
Interest rate derivatives, derivative not designated as hedging instruments, classified in other liabilities	$ 53,000		$ 53,000
Not Designated as Hedging Instrument [Member] \| Interest Rate Lock Commitments and Forward Contracts \| Commercial Loan Customers
Derivatives, Hedging Activities and Financial Instruments with Off-Balance Sheet Risk
Derivative, number of transactions \| item	87		87
Notional Amount	$ 23,667,000		$ 23,667,000
Interest rate derivatives, derivative assets not designated as hedging instruments, classified in other assets	250,000		250,000
Not Designated as Hedging Instrument [Member] \| Other Contracts
Derivatives, Hedging Activities and Financial Instruments with Off-Balance Sheet Risk
Derivative, number of transactions \| item		4
Notional Amount		$ 28,052,000
Derivative assets designated as hedging instruments, classified in other assets	3,021,000		3,021,000
Derivated liabilities designated as hedging instruments, classified in other liabilities	$ 2,824,000		$ 2,824,000
Interest rate derivatives, derivative not designated as hedging instruments, classified in other liabilities		118,000
Interest Income [Member]
Derivatives, Hedging Activities and Financial Instruments with Off-Balance Sheet Risk
Amount to be reclassified as a reduction to interest expense during the next twelve months		625,000
Interest Expense [Member]
Derivatives, Hedging Activities and Financial Instruments with Off-Balance Sheet Risk
Amount to be reclassified as a reduction to interest expense during the next twelve months		$ 600,000

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.

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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)
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- Definition

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

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4B
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- Definition

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

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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

Fair value as of the balance sheet date of derivative instrument not designated as hedging instrument and classified as an asset.

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- Definition

Fair value as of the balance sheet date of derivative instrument not designated as hedging instrument and classified as a liability.

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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
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- Definition

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

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- Definition

Fair value as of the balance sheet date of all interest rate derivative assets designated as cash flow hedging instruments.

+ References

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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.

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Fair value as of the balance sheet date of all interest rate derivative liabilities designated as cash flow hedging instruments.

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Fair value as of the balance sheet date of all derivative assets not designated as hedging instruments.

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Fair value as of the balance sheet date of all derivative liabilities not designated as hedging instruments.

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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.

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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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