Condensed Consolidated Statements of Changes in Shareholders' Equity - USD ($) $ in Thousands	Common Stock	Surplus	Retained Earnings	Accumulated Other Comprehensive Income (Loss).	Total
Balance at Dec. 31, 2015	$ 60,407	$ 703,929	$ 298,919	$ (3,871)	$ 1,059,384
Balance (in shares) at Dec. 31, 2015	24,162,657
Increase (Decrease) in Stockholders' Equity
Comprehensive income			49,010	10,381	59,391
Cash divideends declared on common stock per share			(14,029)		(14,029)
Employee stock purchases	$ 9	218			227
Employee stock purchases (in shares)	3,729
Stock options exercised	$ 60	748			808
Stock options exercised (in shares)	24,073
Restricted stock awards	$ 99	(99)
Restricted stock awards (in shares)	39,556
Stock issued pursuant to restricted stock units.	$ 90	(90)
Stock issued pursuant to restricted stock units (in shares)	35,903
Value of common stock repurchased buyback plan	$ (82)	(2,048)			(2,130)
Common stock repurchased buyback plan (in shares)	(32,900)
Common stock repurchased	$ (95)	(2,377)			(2,472)
Common stock repurchased (in shares)	(37,792)
Share-based compensation expense		3,164			3,164
Balance at Jun. 30, 2016	$ 60,488	703,445	333,900	6,510	$ 1,104,343
Balance (in shares) at Jun. 30, 2016	24,195,226				24,195,226
Balance (in shares) Preferred Stock at Jun. 30, 2016					0
Balance at Dec. 31, 2016	$ 60,576	711,307	370,916	(8,211)	$ 1,134,588
Balance (in shares) at Dec. 31, 2016	24,230,392				24,230,392
Balance (in shares) Preferred Stock at Dec. 31, 2016					0
Increase (Decrease) in Stockholders' Equity
Comprehensive income			50,087	4,514	$ 54,601
Cash divideends declared on common stock per share			(19,297)		(19,297)
Employee stock purchases	$ 8	259			267
Employee stock purchases (in shares)	3,226
Stock options exercised	$ 84	1,050			1,134
Stock options exercised (in shares)	33,896
Common stock issued for Southeastern Bank Financial Corp. acquisition	$ 12,446	422,163			434,609
Common stock issued for Southeastern Bank Financial Corp. acquisition (in shares)	4,978,338
Restricted stock awards	$ 39	(39)
Restricted stock awards (in shares)	15,851
Stock issued pursuant to restricted stock units.	$ 95	(95)
Stock issued pursuant to restricted stock units (in shares)	37,802
Common stock repurchased	$ (100)	(3,505)			(3,605)
Common stock repurchased (in shares)	(40,241)
Share-based compensation expense		3,188			3,188
Balance at Jun. 30, 2017	$ 73,148	$ 1,134,328	$ 401,706	$ (3,697)	$ 1,605,485
Balance (in shares) at Jun. 30, 2017	29,259,264				24,259,264
Balance (in shares) Preferred Stock at Jun. 30, 2017					0