Parent Corporation Only Financial Statements (Details) - Condensed Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Cash flows from operating activities:
Net income	$ 18,672	$ 19,902	$ 17,527	$ 4,251	$ 10,580	$ 13,077	$ 7,683	$ 11,880	$ 60,352	$ 43,220	$ 31,082
Adjustments to reconcile net income to net cash provided by operating activities:
Loss on equity securities, net									267
(Increase) decrease in other assets									(1,134)	5,706	(15,006)
Increase (decrease) in other liabilities									4,988	3,887	(2,022)
Net cash provided by operating activities									89,060	131,133	49,712
Cash flows from investing activities:
Net cash used in investing activities									(357,214)	(817,727)	(427,669)
Cash flows from financing activities:
Cash dividends on common stock									(9,664)	(9,612)	(9,067)
Cash dividends on preferred stock											(22)
Issuance cost of common stock										(180)
Redemption of preferred stock											(11,250)
Proceeds from exercise of stock options									875	417	767
Net cash provided by financing activities									290,938	635,777	377,461
Increase (decrease) in cash and cash equivalents									22,784	(50,817)	(496)
Cash and cash equivalents at beginning of period				149,582					149,582	200,399	200,895
Cash and cash equivalents at end of period	172,366				149,582				172,366	149,582	200,399
Parent Company [Member]
Cash flows from operating activities:
Net income									60,352	43,220	31,082
Adjustments to reconcile net income to net cash provided by operating activities:
Equity in undistributed earnings of subsidiary									(49,235)	(33,458)	(21,926)
Loss on equity securities, net									4
(Increase) decrease in other assets									(627)	269	2,023
Increase (decrease) in other liabilities									3,843	(151)	544
Net cash provided by operating activities									14,337	9,880	11,723
Cash flows from investing activities:
Purchase of available-for-sale securities									(8)	(7)
Capital infusion to subsidiary									(64,500)		(38,439)
Net cash used in investing activities									(64,508)	(7)	(38,439)
Cash flows from financing activities:
Cash dividends on common stock									73,525	(9,612)	(9,067)
Cash dividends on preferred stock									(9,664)		(22)
Issuance cost of common stock										(180)
Secondary offering of common stock											38,439
Redemption of preferred stock											(11,250)
Proceeds from exercise of stock options									875	417	767
Net cash provided by financing activities									64,736	(9,375)	18,867
Increase (decrease) in cash and cash equivalents									14,565	498	(7,849)
Cash and cash equivalents at beginning of period				$ 7,506					7,506	7,008	14,857
Cash and cash equivalents at end of period	$ 22,071				$ 7,506				$ 22,071	$ 7,506	$ 7,008