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, 2014	$ 497	$ 576,504	$ 423,956	$ (17,027)	$ (119,749)	$ 864,181
Net income	0	0	18,166	0	0	18,166
Cash dividends	0	0	(9,282)	0	0	(9,282)
Net issuance of shares to employee benefit plans and other stock plans, including tax benefit	0	(2,564)	0	0	1,509	(1,055)
Stock-based compensation	0	1,988	0	0	0	1,988
Other comprehensive income	0	0	0	3,496	0	3,496
Ending Balance at Mar. 31, 2015	497	575,928	432,840	(13,531)	(118,240)	877,494
Beginning Balance at Dec. 31, 2015	497	576,726	462,232	(22,418)	(135,033)	882,004
Net income	0	0	18,891	0	0	18,891
Cash dividends	0	0	(9,473)	0	0	(9,473)
Purchases of treasury shares	0	0	0	0	(17,193)	(17,193)
Net issuance of shares to employee benefit plans and other stock plans, including tax benefit	0	(4,584)	0	0	1,923	(2,661)
Stock-based compensation	0	1,612	0	0	0	1,612
Other comprehensive income	0	0	0	8,547	0	8,547
Ending Balance at Mar. 31, 2016	$ 497	$ 573,754	$ 471,650	$ (13,871)	$ (150,303)	$ 881,727