Consolidated Statements of Shareholders' Equity - USD ($) $ in Thousands	Total	Common Stock	Treasury Stock	Additional paid in capital	Retained earnings	Accumulated other comprehensive income (loss)
Balance at Dec. 31, 2015	$ 350,829	$ 201	$ (1,743)	$ 210,589	$ 141,564	$ 218
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	48,837	0	0	0	48,837	0
Other comprehensive income (loss)	(1,959)	0	0	0	0	(1,959)
Cash dividends paid on common shares	(8,211)	0	0	0	(8,211)	0
Repurchase of preferred stock	(4,889)	0	(4,889)	0	0	0
Issuance under equity compensation plans, net	(2,203)	2	0	(2,205)	0	0
Share-based compensation	3,367	0	0	3,367	0	0
Excess tax benefit related to equity compensation plans	1,327	0	0	1,327	0	0
Balance at Dec. 31, 2016	387,098	203	(6,632)	213,078	182,190	(1,741)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	48,190	0	0	0	48,190	0
Other comprehensive income (loss)	(2,077)	0	0	0	0	(2,077)
Cash dividends paid on common shares	(10,249)	0	0	0	10,249	0
Repurchase of preferred stock	(16,636)	0	(16,636)	0	0	0
Issuance under equity compensation plans, net	(2,909)	2	0	(2,911)	0	0
Shares issued in connection with acquisition of Jefferson County Bancshares, Inc., 3,299,865 shares, net	141,729	33	0	141,696	0	0
Share-based compensation	3,427	0	0	3,427	0	0
Reclassification for the adoption of ASU 2016-09	0	0	0	(5,229)	5,229	0
Balance at Dec. 31, 2017	548,573	238	(23,268)	350,061	225,360	(3,818)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	89,217	0	0	0		0
Other comprehensive income (loss)	(4,630)	0	0	0	0	(4,630)
Cash dividends paid on common shares	(10,845)	0	0	0	(10,845)	0
Repurchase of preferred stock	(19,387)	0	(19,387)	0	0	0
Issuance under equity compensation plans, net	(2,576)	1	0	(2,577)	0	0
Share-based compensation	3,452	0	0	3,452	0	0
Reclassification for the adoption of ASU 2016-09	0	0	0	0	834	(834)
Balance at Dec. 31, 2018	$ 603,804	$ 239	$ (42,655)	$ 350,936	$ 304,566	$ (9,282)