Consolidated Statement of Changes in Equity (USD $) In Thousands, unless otherwise specified	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Noncontrolling Interest [Member]
Balance at at Dec. 31, 2009	$ 159,186	$ 11,086	$ 27,527	$ 125,282	$ (9,690)	$ 4,981
Net income	34,404	0	0	32,120	0	2,284
Currency translation adjustments	805	0	0	0	328	477
Defined Benefit Plans [Abstract]
Net gain (loss) arising during the period, other	(6,267)	0	0	0	(6,267)	0
Amortization of actuarial loss	1,832	0	0	0	1,832	0
Amortization of prior service cost	91	0	0	0	91	0
Amortization of Initial Net Asset	(3)	0	0	0	(3)	0
Current period changes in fair value of derivatives	708	0	0	0	708	0
Unrealized gain on available-for-sale securities	248	0	0	0	248	0
Dividends Common Stock	(10,600)	0	0	(10,600)	0	0
Dividends paid to noncontrolling interest	(1,021)	0	0	0	0	(1,021)
Shares issued upon exercise of stock options and other	5,262	297	4,965	0	0	0
Shares issued for empoyee stock purchase plan	238	10	228	0	0	0
Equity-based compensation plans	3,096	99	2,997	0	0	0
Excess tax benefit from stock option exercises	2,558	0	2,558	0	0	0
Balance at at Dec. 31, 2010	190,537	11,492	38,275	146,802	(12,753)	6,721
Net income	48,223	0	0	45,892	0	2,331
Currency translation adjustments	(9,155)	0	0	0	(8,080)	(1,075)
Defined Benefit Plans [Abstract]
Net gain (loss) arising during the period, other	(9,698)	0	0	0	(9,698)	0
Amortization of actuarial loss	1,230	0	0	0	1,230	0
Amortization of prior service cost	77	0	0	0	77	0
Amortization of Initial Net Asset	0
Current period changes in fair value of derivatives	395	0	0	0	395	0
Unrealized gain on available-for-sale securities	(138)	0	0	0	(138)	0
Dividends Common Stock	(11,984)	0	0	(11,984)	0	0
Dividends paid to noncontrolling interest	(1,000)	0	0	0	0	(1,000)
Stock offering, net of related expenses	48,143	1,265	46,878	0	0	0
Shares issued upon exercise of stock options and other	858	47	811	0	0	0
Shares issued for empoyee stock purchase plan	247	8	239	0	0	0
Equity-based compensation plans	3,513	100	3,413	0	0	0
Excess tax benefit from stock option exercises	109	0	109	0	0	0
Balance at at Dec. 31, 2011	261,357	12,912	89,725	180,710	(28,967)	6,977
Net income	50,240	0	0	47,405	0	2,835
Currency translation adjustments	(2,111)	0	0	0	(1,974)	(137)
Defined Benefit Plans [Abstract]
Net gain (loss) arising during the period, other	(13,980)	0	0	0	(13,980)	0
Amortization of actuarial loss	1,852	0	0	0	1,852	0
Amortization of prior service cost	76	0	0	0	76	0
Amortization of Initial Net Asset	0
Current period changes in fair value of derivatives	272	0	0	0	272	0
Unrealized gain on available-for-sale securities	866	0	0	0	866	0
Dividends Common Stock	(12,725)	0	0	(12,725)	0	0
Dividends paid to noncontrolling interest	(1,099)	0	0	0	0	(1,099)
Shares issued upon exercise of stock options and other	(1,194)	102	(1,296)	0	0	0
Shares issued for empoyee stock purchase plan	270	7	263	0	0	0
Equity-based compensation plans	3,807	74	3,733	0	0	0
Excess tax benefit from stock option exercises	2,045	0	2,045	0	0	0
Balance at at Dec. 31, 2012	$ 289,676	$ 13,095	$ 94,470	$ 215,390	$ (41,855)	$ 8,576