Condensed Consolidated Statements of Shareholders' Equity (unaudited) $ in Thousands	USD ($)
Balance at beginning of period at Dec. 31, 2016	$ 248,980
Cumulative effect of change in accounting at Dec. 31, 2016	352
Balance at beginning of period, as adjusted at Dec. 31, 2016	249,332
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	18,764
Cash dividends declared	(6,400)
Acquisition of TCSB Bancorp, Inc.	0
Issuance of common stock	57
Share based compensation	1,342
Share based compensation withholding obligation	(536)
Net change in accumulated other comprehensive loss, net of related tax effect	5,151
Balance at end of period at Sep. 30, 2017	267,710
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	6,859
Net change in accumulated other comprehensive loss, net of related tax effect	155
Balance at end of period at Sep. 30, 2017	267,710
Balance at beginning of period at Dec. 31, 2017	264,933
Cumulative effect of change in accounting at Dec. 31, 2017	0
Balance at beginning of period, as adjusted at Dec. 31, 2017	264,933
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	29,903
Cash dividends declared	(10,446)
Acquisition of TCSB Bancorp, Inc.	64,536
Issuance of common stock	202
Share based compensation	1,293
Share based compensation withholding obligation	(1,327)
Net change in accumulated other comprehensive loss, net of related tax effect	(3,890)
Balance at end of period at Sep. 30, 2018	345,204
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	11,925
Net change in accumulated other comprehensive loss, net of related tax effect	(675)
Balance at end of period at Sep. 30, 2018	$ 345,204