Consolidated Statement of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statement of Comprehensive Income [Abstract]
Net income	$ 73,548	$ 72,100	$ 40,847
Other comprehensive income (loss)
Net unrealized holding gains (losses) arising during period on investment securities available for sale, net of tax expense (benefit) of $(169), ($2,355) and ($1,239)	(314)	(4,374)	(2,300)
Reclassification adjustment for gains on investment securities included in earnings, net of tax of $13, $33 and $48	(24)	(61)	(89)
Net unrealized gains (losses) on cash flow hedge during the period, net of tax expense (benefit) of $63, $13 and ($192)	116	24	(356)
Total other comprehensive income (loss)	(222)	(4,411)	(2,745)
Comprehensive income	$ 73,326	$ 67,689	$ 38,102