Consolidated Statements of Shareholders' Equity (USD $) In Thousands, unless otherwise specified	Total	Common Stock	Retained Earnings	Common Stock In Treasury	Other Comprehensive Income (Loss)	Other Equity Transactions
Beginning balances at Dec. 31, 2009	$ 339,859	$ 173,776	$ 321,974	$ (111,370)	$ (46,684)	$ 2,163
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	46,427		46,427
Other comprehensive income	(4,932)				(4,932)
Proceeds from exercise of 154, 53 and 17 shares under option plans for the years ended 2010, 2011 and 2012, respectively	2,631	2,631
Income tax benefit from exercise of stock compensation realization	120	120
Repurchase of 150, 132 and 6 shares for the years ended 2010, 2011 and 2012, respectively	(3,527)			(3,527)
Stock-based compensation expense	4,100	4,100
Shares withheld for employee taxes on equity awards	(481)	(481)
Directors' deferred compensation	145			(192)		337
Other equity transactions	14	15		(1)
Ending balances at Dec. 31, 2010	384,356	180,161	368,401	(115,090)	(51,616)	2,500
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	39,979		39,979
Other comprehensive income	(20,599)				(20,599)
Proceeds from exercise of 154, 53 and 17 shares under option plans for the years ended 2010, 2011 and 2012, respectively	735	735
Income tax benefit from exercise of stock compensation realization	658	658
Repurchase of 150, 132 and 6 shares for the years ended 2010, 2011 and 2012, respectively	(3,776)			(3,776)
Stock-based compensation expense	5,000	5,000
Shares withheld for employee taxes on equity awards	(641)	(641)
Directors' deferred compensation	270			587		317
Ending balances at Dec. 31, 2011	405,982	185,913	408,380	(118,279)	(72,215)	2,183
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	24,664		24,664
Other comprehensive income	(16,214)				(16,214)
Proceeds from exercise of 154, 53 and 17 shares under option plans for the years ended 2010, 2011 and 2012, respectively	158	158
Cash dividends declared	(4,650)		(4,650)
Income tax benefit from exercise of stock compensation realization	817	817
Repurchase of 150, 132 and 6 shares for the years ended 2010, 2011 and 2012, respectively	(119)			(119)
Stock-based compensation expense	5,889	5,889
Shares withheld for employee taxes on equity awards	(1,608)	(1,608)
Directors' deferred compensation	76			100		(24)
Ending balances at Dec. 31, 2012	$ 414,995	$ 191,169	$ 428,394	$ (118,298)	$ (88,429)	$ 2,159