Consolidated Statements of Shareholders' Equity - USD ($) $ in Thousands	Total	Common Stock	Retained Earnings	Common Stock In Treasury	Accumulated Other Comprehensive Income (Loss)	Other Equity Transactions
Beginning balances at Dec. 31, 2014	$ 459,019	$ 204,634	$ 474,633	$ (140,938)	$ (82,237)	$ 2,927
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	32,158	0	32,158	0	0	0
Other comprehensive income (loss)	1,532	0	0	0	1,532	0
Cash dividends declared	(7,132)	0	(7,132)	0	0	0
Stock-based compensation activity	4,260	4,260	0	0	0	0
Repurchase of 212, 147, and 32 shares for the years ended 2015, 2016, and 2017, respectively	(7,129)	0	0	(7,129)	0	0
Directors' deferred compensation	249	73	0	(492)	0	668
Ending balances at Dec. 31, 2015	482,957	208,967	499,659	(148,559)	(80,705)	3,595
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	25,740	0	25,740	0	0	0
Other comprehensive income (loss)	(5,476)	0	0	0	(5,476)	0
Cash dividends declared	(7,496)	0	(7,496)	0	0	0
Stock-based compensation activity	2,002	3,764	0	(1,762)	0	0
Repurchase of 212, 147, and 32 shares for the years ended 2015, 2016, and 2017, respectively	(3,798)	0	0	(3,798)	0	0
Directors' deferred compensation	160	(29)	0	(280)	0	469
Ending balances at Dec. 31, 2016	494,089	212,702	517,903	(154,399)	(86,181)	4,064
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	11,451	0	11,451	0	0	0
Other comprehensive income (loss)	(16,756)	0	0	0	(2,081)	0
Other Comprehensive Income (Loss) Net of Tax Reform	(2,081)
Tax Cuts and Jobs Act of 2017 Reclassification	0	0	14,675	0	(14,675)	0
Cash dividends declared	(7,913)	0	(7,913)	0	0	0
Stock-based compensation activity	450	10,750	0	(10,300)	0	0
Repurchase of 212, 147, and 32 shares for the years ended 2015, 2016, and 2017, respectively	(1,086)	0	0	(1,086)	0	0
Directors' deferred compensation	71	32	0	(343)	0	382
Ending balances at Dec. 31, 2017	$ 494,981	$ 223,484	$ 536,116	$ (166,128)	$ (102,937)	$ 4,446