Consolidated Statements of Changes in Stockholders' Equity (USD $) In Thousands	Total	Common Stock [Member]	Additional Paid-in-Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive (Loss) Income [Member]	Common Stock in Treasury [Member]
Beginning Balance at Dec. 31, 2009	$ 505,123	$ 380	$ 311,164	$ 270,232	$ 1,163	$ (77,816)
Net income	57,404	0	0	57,404	0	0
Cash dividends	(27,577)	0	0	(27,577)	0	0
Net issuance of common shares	(477)	0	0	0	0	(477)
Net issuance of shares to employee stock plans, including tax benefit	1,815	0	(923)	(262)	0	3,000
Stock-based compensation	3,782	0	3,782	0	0	0
Other comprehensive income	(6,498)	0	0	0	(6,498)	0
Ending Balance at Dec. 31, 2010	533,572	380	314,023	299,797	(5,335)	(75,293)
Net income	57,901	0	0	57,901	0	0
Cash dividends	(27,063)	0	0	(27,063)	0	0
Purchases of treasury shares	(30,502)	0	0	0	0	(30,502)
Net issuance of shares to employee stock plans, including tax benefit	1,727	0	62	(654)	0	2,319
Stock-based compensation	3,244	0	3,244	0	0	0
Other comprehensive income	(769)	0	0	0	(769)	0
Ending Balance at Dec. 31, 2011	538,110	380	317,329	329,981	(6,104)	(103,476)
Net income	54,558	0	0	54,558	0	0
Cash dividends	(26,712)	0	0	(26,712)	0	0
Purchases of treasury shares	(15,490)	0	0	0	0	(15,490)
Net issuance of shares for acquisition	25,824	13	25,811	0	0	0
Net issuance of shares to employee stock plans, including tax benefit	1,395	0	(812)	(269)	0	2,476
Stock-based compensation	4,364	0	4,364	0	0	0
Other comprehensive income	224	0	0	0	224	0
Ending Balance at Dec. 31, 2012	$ 582,273	$ 393	$ 346,692	$ 357,558	$ (5,880)	$ (116,490)