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, 2016		$ 31,622	$ 101,730	$ 577,648	$ 94
Shares issued for stock options		160	2,592
Stock-based compensation arrangements			222
Net income	$ 22,050			22,050
Dividends on common stock				(6,067)
Net change	(178)				(178)
Balance at end of period at Mar. 31, 2017	729,873	31,782	104,544	593,631	(84)
Balance at beginning of period at Dec. 31, 2017	775,629	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)