Consolidated statements of comprehensive income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statement Of Income And Comprehensive Income [Abstract]
Net income	$ 52,398	$ 40,591	$ 47,856
Other comprehensive income, net of tax:
Net change in unrealized loss (gain) in available-for-sale securities, net of taxes of $493, $5,309 and $(71)	1,162	778	(1,057)
Reclassification adjustment for (gain) on sale of securities included in net income, net of tax expenses of $112, $298, and $91	(173)	(4,109)	(1,753)
Net change in unrealized gain in hedging activities, net of taxes of $442, $-, and $-	685
Comprehensive income	$ 54,072	$ 37,260	$ 45,046