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, 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 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
Beginning Balance at Dec. 31, 2014	497	576,504	423,956	(17,027)	(119,749)	864,181
Net income	0	0	37,447	0	0	37,447
Cash dividends	0	0	(18,957)	0	0	(18,957)
Purchases of treasury shares	0	0	0	0	(10,672)	(10,672)
Net issuance of shares to employee benefit plans and other stock plans, including tax benefit	0	(3,568)	0	0	4,060	492
Stock-based compensation	0	2,676	0	0	0	2,676
Other comprehensive income	0	0	0	804	0	804
Ending Balance at Jun. 30, 2015	$ 497	$ 575,612	$ 442,446	$ (16,223)	$ (126,361)	$ 875,971