Securities (Details Textual) (Details) - USD ($)	3 Months Ended	12 Months Ended
Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities	$ 445,750,000		$ 447,498,000
Other than Temporary Impairment Losses, Investments, Portion Recognized in Earnings, Net	0	$ 0
Other than Temporary Impairment, Credit Losses Recognized in Earnings, Credit Losses on Debt Securities Held	0	$ 0
Securities (Textual) [Abstract]
Callable Securities in Investment Portfolio	7,400,000
Pledged Financial Instruments, Not Separately Reported, Securities	552,700,000		547,200,000
Trading	1,601,000		1,324,000
Investments in obligations of individual states, counties or municipalities which exceed 10% of equity	0		0
Trading Securities, Equity	$ 20,075,000		0
Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities			$ 20,584,000

Callable securities in investment portfolio.

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Investments in obligations of individual states, counties or municipalities which exceed 10% of equity

+ References

No definition available.

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- Definition

Securities.

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No definition available.

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Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

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- Definition

The cumulative amount of credit losses recognized in earnings related to debt securities held for which a portion of an other than temporary impairment (OTTI) was recognized in other comprehensive income (a component of shareholders' equity).

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The amount of other than temporary impairment (OTTI) losses on equity securities, OTTI related to credit losses on debt securities, and OTTI losses on debt securities when the entity intends to sell the securities or it is more likely than not that the entity will be required to sell the securities before recovery of its amortized cost basis. Additionally, this item includes OTTI losses recognized during the period on investments accounted for under the cost method of accounting.

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Sum of the carrying amounts as of the date of the latest financial statement presented of securities which are owned but transferred to another party to serve as collateral to partially or fully secure a debt obligation, repurchase agreement or other current or potential obligation, and for which the transferee is not permitted to sell or re-pledge them to an unrelated party.

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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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Amount of investments in debt and equity securities and other forms of securities that provide ownership interests classified as trading.

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Fair value of investments in trading equity securities and other forms of trading securities that provide ownership interests.

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