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, 2015		$ 15,597	$ 102,865	$ 535,521	$ 1,527
Shares issued, Value		31	871
Shares acquired and canceled, Value		(100)		(5,423)
Tax effect of stock options			(209)
Stock-based compensation arrangements			451
Net income	$ 16,579			16,579
Dividends on common stock				(5,579)
Net change	530				530
Balance at end of period at Mar. 31, 2016	662,661	15,528	103,978	541,098	2,057
Balance at beginning of period at Dec. 31, 2016	711,094	15,811	117,541	577,648	94
Shares issued, Value		80	2,672
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	$ 15,891	$ 120,435	$ 593,631	$ (84)