Investment Securities (Details Textual)	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2018 USD ($) Investment	Jun. 30, 2017 USD ($)	Jun. 30, 2018 USD ($) Security Investment	Jun. 30, 2017 USD ($)	Dec. 31, 2017 USD ($) Security
Investments Debt And Equity Securities [Abstract]
Carrying value of investment securities for pledge	$ 64,300,000		$ 64,300,000		$ 105,000,000
Investment securities with fair value less than amortized cost | Security			123		83
OTTI loss recognized through impairment assessment process	$ 0	$ 0	$ 0	$ 0
Non-accrual investment securities					$ 895,000
Trust preferred securities in nonaccrual status | Investment	2		2