Condensed Consolidated Statements of Shareholders' Equity (unaudited) - USD ($) $ in Thousands	Common Stock [Member]	Accumulated Deficit [Member]	Accumulated Other Comprehensive Loss [Member]	Total
Balance at beginning of period at Dec. 31, 2017	$ 324,986	$ (54,054)	$ (5,999)	$ 264,933
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income		29,903		29,903
Cash dividends declared	0	(10,446)	0	(10,446)
Acquisition of TCSB Bancorp, Inc.	64,536	0	0	64,536
Repurchase of common stock	0
Issuance of common stock	202	0	0	202
Share based compensation	1,293	0	0	1,293
Share based compensation withholding obligation	(1,327)	0	0	(1,327)
Other comprehensive income (loss)	0	0	(3,890)	(3,890)
Balances at end of period at Sep. 30, 2018	389,690	(34,597)	(9,889)	345,204
Balance at beginning of period at Jun. 30, 2018	389,196	(42,899)	(9,214)	337,083
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income		11,925		11,925
Cash dividends declared	0	(3,623)	0	(3,623)
Issuance of common stock	55	0	0	55
Share based compensation	445	0	0	445
Share based compensation withholding obligation	(6)	0	0	(6)
Other comprehensive income (loss)	0	0	(675)	(675)
Balances at end of period at Sep. 30, 2018	389,690	(34,597)	(9,889)	345,204
Balance at beginning of period at Dec. 31, 2018	377,372	(28,270)	(10,108)	338,994
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income		32,556		32,556
Cash dividends declared	0	(12,507)	0	(12,507)
Repurchase of common stock	(26,284)	0	0	(26,284)
Issuance of common stock	282	0	0	282
Share based compensation	1,348	0	0	1,348
Share based compensation withholding obligation	(879)	0	0	(879)
Other comprehensive income (loss)	0	0	6,735	6,735
Balances at end of period at Sep. 30, 2019	351,839	(8,221)	(3,373)	340,245
Balance at beginning of period at Jun. 30, 2019	351,894	(16,617)	(4,431)	330,846
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income		12,445		12,445
Cash dividends declared	0	(4,049)	0	(4,049)
Repurchase of common stock	(502)	0	0	(502)
Issuance of common stock	0	0	0	0
Share based compensation	460	0	0	460
Share based compensation withholding obligation	(13)	0	0	(13)
Other comprehensive income (loss)	0	0	1,058	1,058
Balances at end of period at Sep. 30, 2019	$ 351,839	$ (8,221)	$ (3,373)	$ 340,245