Consolidated Statements of Stockholders' Equity (unaudited) (USD $) In Thousands	Common Stock [Member]	Additional Paid-in-Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Common Stock in Treasury [Member]	Total
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)
Purchases of treasury shares	0	0	0	0	(5,460)	(5,460)
Issuance of shares, net of treasury 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 (loss) 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
Beginning Balance at Dec. 31, 2013	497	574,152	385,787	(16,765)	(127,102)	816,569
Net income	0	0	45,649	0	0	45,649
Cash dividends	0	0	(18,425)	0	0	(18,425)
Purchases of treasury shares	0	0	0	0	(72)	(72)
Net issuance of shares to employee benefit plans and other stock plans, including tax benefit	0	(2,232)	0	0	3,360	1,128
Stock-based compensation	0	2,082	0	0	0	2,082
Other comprehensive (loss) income	0	0	0	10,210	0	10,210
Ending Balance at Jun. 30, 2014	$ 497	$ 574,002	$ 413,011	$ (6,555)	$ (123,814)	$ 857,141