Consolidated Statements of Comprehensive Income (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statement of Comprehensive Income [Abstract]
Unrealized gains arising during the period, net of tax benefit	$ 3,224	$ 7,477	$ 1,561
Reclassification adjustment for gains included in net income, net of tax expense	230	249	288
Unrealized (losses) gains arising during the period, net of tax (benefit) expense	(426)	2,739	1,887
Reclassification adjustment for gains included in net income, net of tax expense	26	685	1,035
Unrealized (losses) gains arising during the period, net of tax (benefit) expense	$ (1)	$ 161	$ (1,766)