Securities (Additional Information) (Details)	12 Months Ended
Dec. 31, 2009 USD ($)	Mar. 31, 2019 USD ($) investment	Dec. 31, 2018 USD ($) investment
Debt Securities, Available-for-sale [Line Items]
Carrying value of securities pledged to secure repurchase agreements, public and trust deposits and other by law		$ 209,016,000	$ 211,239,000
Original amount in non-controlling investment security in a single banking organization		353,000	$ 353,000
Additional impairment on equity securities recognized through earnings		$ 0
Equity Securities
Debt Securities, Available-for-sale [Line Items]
Number of non-controlling investments in a single banking organization \| investment		1	1
Original amount in non-controlling investment security in a single banking organization	$ 1,350,000
Other than temporary impairment loss recognized in earnings, non-controlling investment in single banking organization	$ 997,000

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- Definition

Carrying value of securities sold under agreements to repurchase and deposits received for securities loaned.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08.(m)(1))
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03.13(1))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

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- Definition

Amount of investment in equity security without readily determinable fair value.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 321
-SubTopic 10
-Section 50
-Paragraph 3
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=84241550&loc=SL75117539-209714

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- Definition

Amount of cumulative impairment loss on investment in equity security without readily determinable fair value.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 321
-SubTopic 10
-Section 50
-Paragraph 3
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=84241550&loc=SL75117539-209714

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The amount of other than temporary impairment losses on investments in debt and equity securities categorized as Available-for-sale which have been recognized in earnings during the period. Such impairment losses consist of other than temporary impairments (OTTI) on equity securities, credit losses on investments in debt securities, and when the entity intends to sell an impaired debt security or it is more likely than not that the entity will be required to sell the impaired debt security before recovery of its amortized cost basis.

+ References

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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.

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No definition available.

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