Segment Geographic and Market Information (Details 1) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010	Sep. 30, 2010	Jun. 30, 2010	Mar. 31, 2010	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Geographic information
Sales to unaffiliated customers shipped	$ 233,661	$ 248,044	$ 242,876	$ 217,788	$ 219,387	$ 228,822	$ 218,825	$ 174,003	$ 942,369	$ 841,037	$ 691,864
Operating profit from sales	20,190	27,053	21,827	18,583	12,323	22,672	23,878	11,168	87,653	70,041	52,877
Account receivable	206,834				193,968				206,834	193,968	148,260
Property, plant, equipment, and mineral rights and reserves	262,577				260,488				262,577	260,488	236,246
Identifiable assets	842,702				799,093				842,702	799,093	734,260
Americas [Member]
Geographic information
Sales to unaffiliated customers shipped									589,277	531,133	441,483
Operating profit from sales									57,088	45,818	27,236
Account receivable	111,704				108,324				111,704	108,324	76,723
Property, plant, equipment, and mineral rights and reserves	115,720				110,198				115,720	110,198	108,352
Identifiable assets	420,973				433,130				420,973	433,130	453,894
EMEA [Member]
Geographic information
Sales to unaffiliated customers shipped									220,067	185,506	168,202
Operating profit from sales									12,543	6,455	14,124
Account receivable	54,245				47,318				54,245	47,318	41,401
Property, plant, equipment, and mineral rights and reserves	98,067				100,680				98,067	100,680	80,693
Identifiable assets	282,163				252,065				282,163	252,065	197,897
Asia Pacific [Member]
Geographic information
Sales to unaffiliated customers shipped									133,025	124,398	82,179
Operating profit from sales									18,022	17,768	11,517
Account receivable	40,885				38,326				40,885	38,326	30,136
Property, plant, equipment, and mineral rights and reserves	48,790				49,610				48,790	49,610	47,201
Identifiable assets	$ 139,566				$ 113,898				$ 139,566	$ 113,898	$ 82,469