Fair Value Measurements - Summary of assets and liabilities measured at fair value on recurring basis (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Available-for-sale securities
Fair Value	$ 146,419	$ 145,698
Fair Value, Assets, Level 1 to Level 2 Transfers, Amount	0
Fair Value, Assets, Level 2 to Level 1 Transfers, Amount	0
Fair Value
Available-for-sale securities
Fair Value	146,419	145,698
Fair Value \| (Level 1)
Available-for-sale securities
Fair Value	0	0
Fair Value \| (Level 2)
Available-for-sale securities
Fair Value	146,419	145,698
Fair Value \| (Level 3)
Available-for-sale securities
Fair Value	0	0
Recurring \| (Level 1)
Available-for-sale securities
Fair Value	0	0
Recurring \| (Level 1) \| Mortgage-backed securities - agency
Available-for-sale securities
Fair Value	0	0
Recurring \| (Level 1) \| Collateralized mortgage obligations (CMO's) - agency
Available-for-sale securities
Fair Value	0	0
Recurring \| (Level 2)
Available-for-sale securities
Fair Value	146,419	145,698
Recurring \| (Level 2) \| Mortgage-backed securities - agency
Available-for-sale securities
Fair Value	25,037	26,675
Recurring \| (Level 2) \| Collateralized mortgage obligations (CMO's) - agency
Available-for-sale securities
Fair Value	121,382	119,023
Recurring \| (Level 3)
Available-for-sale securities
Fair Value	0	0
Recurring \| (Level 3) \| Mortgage-backed securities - agency
Available-for-sale securities
Fair Value	0	0
Recurring \| (Level 3) \| Collateralized mortgage obligations (CMO's) - agency
Available-for-sale securities
Fair Value	0	0
Non-recurring
Available-for-sale securities
Assets	$ 0	$ 0

Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=99377789&loc=d3e19207-110258

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- References

No definition available.

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- Definition

Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 45
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=109979856&loc=d3e26610-111562

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (aa)
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- Definition

Amount of transfers of assets measured on a recurring basis out of Level 1 of the fair value hierarchy into Level 2.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
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-URI http://asc.fasb.org/extlink&oid=99377789&loc=d3e19207-110258

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Amount of transfers of assets measured on a recurring basis out of Level 2 of the fair value hierarchy into Level 1.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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