Consolidated Statements of Stockholders' Equity (Unaudited) (USD $) In Thousands	Common Stock [Member]	Additional Paid-in-Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive (Loss) Income [Member]	Common Stock in Treasury [Member]	Total
Beginning Balance at Dec. 31, 2011	$ 380	$ 317,329	$ 329,981	$ (6,104)	$ (103,476)	$ 538,110
Net income	0	0	26,907	0	0	26,907
Cash dividends	0	0	(13,232)	0	0	(13,232)
Purchase of treasury shares	0	0	0	0	(15,490)	(15,490)
Net issuance of shares for acquisition	13	25,811	0	0	0	25,824
Net issuance of shares to employee benefit plans and other stock plans, including tax benefit	0	(753)	(196)	0	1,641	692
Stock-based compensation	0	2,797	0	0	0	2,797
Other comprehensive income	0	0	0	897	0	897
Ending Balance at Jun. 30, 2012	393	345,184	343,460	(5,207)	(117,325)	566,505
Beginning Balance at Dec. 31, 2012	393	346,692	357,558	(5,880)	(116,490)	582,273
Net income	0	0	24,565	0	0	24,565
Cash dividends	0	0	(15,568)	0	0	(15,568)
Purchase of treasury shares	0	0	0	0	(5,460)	(5,460)
Net issuance of shares for acquisition	104	225,447	0	0	(5,779)	219,772
Net issuance of shares to employee benefit plans and other stock plans, including tax benefit	0	(2,506)	0	0	1,479	(1,027)
Stock-based compensation	0	2,726	0	0	0	2,726
Other comprehensive income	0	0	0	(15,706)	0	(15,706)
Ending Balance at Jun. 30, 2013	$ 497	$ 572,359	$ 366,555	$ (21,586)	$ (126,250)	$ 791,575