(Parent Company Only) Financial Information - Summary of Statement of Cash Flows (Details) - USD ($) $ in Thousands		12 Months Ended
	Feb. 21, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Adjustments to reconcile net income to net cash provided by operating activities:
Net Income		$ 42,865	$ 29,202	$ 22,141
Gain on sale of VISA stock		(15,153)	0	0
Net (increase) decrease in other assets		5,506	11,573	4,828
Increase (Decrease) in Other Operating Liabilities		(21,432)	2,979	(628)
Net cash used in operating activities		48,909	62,007	29,509
Cash flows from investing activities
Investment in VISA stock		(6,180)	0	0
Net cash provided by (used in) investment activities		(245,576)	(511,785)	(170,901)
CASH FLOWS FROM FINANCING ACTIVITIES
Issuance of common stock, net of related expense	$ 56,700	55,641	0	0
Net cash provided by financing activities		196,527	423,355	176,920
Net change in cash		(140)	(26,423)	35,528
Cash and cash equivalents at beginning of year		109,644	136,067	100,539
Cash and cash equivalents at end of year		109,504	109,644	136,067
Supplemental disclosure of cash flow information:
Cash paid during the period for interest		15,125	7,855	6,636
Parent Company [Member]
Adjustments to reconcile net income to net cash provided by operating activities:
Net Income		42,865	29,202	22,141
Equity in undistributed income of subsidiaries		(33,694)	(30,626)	(23,353)
Gain on sale of VISA stock		(15,153)	0	0
Net (increase) decrease in other assets		1,415	(12)	10
Increase (Decrease) in Other Operating Liabilities		4,005	12	(48)
Net cash used in operating activities		(562)	(1,424)	(1,250)
Cash flows from investing activities
Net cash paid for bank acquisition		(27,862)	(28,905)	0
Investment in unconsolidated subsidiary		0	(200)	0
Investment in VISA stock		(6,180)	0	0
Decrease (increase) in securities purchased under agreement to resell, maturing within 30 days, net		(20,475)	30,647	(5,487)
Net cash provided by (used in) investment activities		(54,517)	1,542	(5,487)
CASH FLOWS FROM FINANCING ACTIVITIES
Issuance of common stock, net of related expense		55,641	0	0
Subordinated debt increase		0	0	6,494
Stock based employment plans		(56)	166	127
Net cash provided by financing activities		55,585	166	6,621
Net change in cash		506	284	(116)
Cash and cash equivalents at beginning of year		648	364	480
Cash and cash equivalents at end of year		1,154	648	364
Supplemental disclosure of cash flow information:
Cash paid during the period for interest		$ 2,205	$ 1,824	$ 1,487