Pending Acquisition of Bank of Rio Vista (Details) $ in Thousands	3 Months Ended	6 Months Ended		9 Months Ended
	Sep. 30, 2018 USD ($) shares	Jun. 30, 2018 USD ($) shares	Jun. 30, 2017 USD ($)	Sep. 30, 2018 USD ($) shares
Acquisition [Abstract]
Increase in recorded investment		$ 164	$ 0
Bank of Rio Vista [Member]
Acquisition [Abstract]
Total ownership of shares (in shares) | shares		1,586
Percentage of ownership of common shares outstanding		39.65%
Total price paid for common shares		$ 12,000
Increase in recorded investment		$ 164
Bank of Rio Vista [Member] | Forecast [Member]
Acquisition [Abstract]
Total ownership of shares (in shares) | shares	2,414			2,414
Percentage of ownership of common shares outstanding	60.35%			60.35%
Total price paid for common shares	$ 28,700			$ 40,700
Multiple of minimum book value to be delivered at close				1.42