Consolidated Statements of Stockholders' Equity (Unaudited) - USD ($) $ in Thousands	Total	COMMON STOCK [Member]	CAPITAL SURPLUS [Member]	RETAINED EARNINGS [Member]	ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) [Member]
Balance at beginning of period at Dec. 31, 2017		$ 31,895	$ 107,481	$ 638,580	$ (2,327)
Shares issued for stock options		80	1,210
Shares issued for acquisitions		733	38,765
Stock-based compensation arrangements			306
Net income	$ 29,620			29,620
Dividends on common stock				(6,859)
Net change	(1,388)				(1,388)
Balance at end of period at Mar. 31, 2018	838,096	32,708	147,762	661,341	(3,715)
Balance at beginning of period at Dec. 31, 2018	902,789	32,604	149,709	722,615	(2,139)
Shares issued for stock options		14	312
Stock-based compensation arrangements			174
Net income	31,837			31,837
Dividends on common stock				(9,739)
Net change	2,540				2,540
Balance at end of period at Mar. 31, 2019	$ 927,927	$ 32,618	$ 150,195	$ 744,713	$ 401