(Parent Company Only) Financial Information - Summary of Statements of Income (Loss) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income
Gain on sale of VISA stock	$ 15,153	$ 0	$ 0
Total interest income	191,596	148,055	116,417
Interest expense	15,300	8,467	6,930
Other expenses	15,535	13,515	12,209
Income tax provision (benefit) benefit	36,336	14,889	13,527
Net income	42,865	29,202	22,141
Parent Company [Member]
Income
Interest/other	2,104	352	115
Dividends from subsidiary Bank	0	0	0
Gain on sale of VISA stock	15,153	0	0
Total interest income	17,257	352	115
Interest expense	2,499	2,115	1,671
Other expenses	649	462	317
Income (loss) before income taxes and equity in undistributed income of subsidiaries	14,109	(2,225)	(1,873)
Income tax provision (benefit) benefit	4,938	(801)	(661)
Income (loss) before equity in undistributed income of subsidiaries	9,171	(1,424)	(1,212)
Equity in undistributed income of subsidiaries	33,694	30,626	23,353
Net income	$ 42,865	$ 29,202	$ 22,141