CONSOLIDATED STATEMENTS OF CHANGES IN SHAREHOLDERS' EQUITY (Unaudited) - USD ($) $ in Thousands	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [Member]
Common Stock, Shares Outstanding, Beginning Balance at Dec. 31, 2016		17,171,000
Shareholders' Equity, Beginning Balance at Dec. 31, 2016	$ 390,804	$ 1,073	$ 115,123	$ 294,365	$ (19,757)
Net income	11,782			11,782
Total other comprehensive income (loss), net of tax	712				712
Cash dividends declared	(6,592)			(6,592)
Share-based compensation	607		607
Exercise of stock options and issuance of other compensation-related equity awards, shares		22,000
Exercise of stock options and issuance of other compensation-related equity awards, value	472	$ 2	470
Common Stock, Shares Outstanding, Ending Balance at Mar. 31, 2017		17,193,000
Shareholders' Equity, Ending Balance at Mar. 31, 2017	$ 397,785	$ 1,075	116,200	299,555	(19,045)
Common Stock, Shares Outstanding, Beginning Balance at Dec. 31, 2017	17,226,508	17,227,000
Shareholders' Equity, Beginning Balance at Dec. 31, 2017	$ 413,284	$ 1,077	117,961	317,756	(23,510)
Net income	16,211			16,211
Total other comprehensive income (loss), net of tax	(9,165)				(9,165)
Cash dividends declared	(7,462)			(7,462)
Share-based compensation	669		669
Exercise of stock options and issuance of other compensation-related equity awards, shares		35,000
Exercise of stock options and issuance of other compensation-related equity awards, value	$ (456)	$ 2	(458)
Common Stock, Shares Outstanding, Ending Balance at Mar. 31, 2018	17,261,730	17,262,000
Shareholders' Equity, Ending Balance at Mar. 31, 2018	$ 413,081	$ 1,079	$ 118,172	$ 326,505	$ (32,675)