Other Real Estate Owned (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Real Estate Acquired Through Foreclosure [Roll Forward]
Balance at beginning of year	$ 10,019	$ 6,300	$ 13,600
Acquisitions	1,200	1,100	0
Additions	5,400	7,600	5,600
Valuation adjustments	(400)	(600)	(200)
Dispositions	(6,100)	(4,400)	(12,700)
Balance at end of year	10,053	10,019	6,300
Write-downs of OREO	400	600	200
Write-down due to change in appraised value	300	550	100
Write-down due to change in management estimates	$ 100	$ 50	$ 100