Segment Information Geographical Locations (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010	Sep. 30, 2010	Jun. 30, 2010	Mar. 31, 2012	Mar. 31, 2011	Mar. 31, 2010
Revenues from External Customers and Long-Lived Assets [Line Items]
Sales and Other Operating Revenues:	$ 780,784	$ 493,888	$ 514,531	$ 361,564	$ 521,713	$ 522,144	$ 559,249	$ 490,956	$ 2,150,767	$ 2,094,062	$ 2,308,299
Property, Plant and Equipment, Net:	259,679				237,088				259,679	237,088	193,224
United States [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Sales and Other Operating Revenues:									428,039	302,992	323,521
Property, Plant and Equipment, Net:	37,658				36,607				37,658	36,607	37,943
Belgium [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Sales and Other Operating Revenues:									221,295	274,534	491,024
China [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Sales and Other Operating Revenues:									207,086	167,676	129,810
Russia [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Sales and Other Operating Revenues:									92,201	153,646	132,565
Germany [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Sales and Other Operating Revenues:									98,642	123,858	121,023
Egypt [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Sales and Other Operating Revenues:									81,156	44,906	99,733
Netherlands [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Sales and Other Operating Revenues:									69,235	107,908	123,705
Indonesia [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Sales and Other Operating Revenues:									72,411	81,808	73,422
Other [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Sales and Other Operating Revenues:									880,702	836,734	813,496
Property, Plant and Equipment, Net:	4,070				3,871				4,070	3,871	3,990
Brazil [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Property, Plant and Equipment, Net:	104,882				85,498				104,882	85,498	46,651
Turkey [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Property, Plant and Equipment, Net:	26,362				28,512				26,362	28,512	29,850
Malawi [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Property, Plant and Equipment, Net:	27,918				31,077				27,918	31,077	30,797
Tanzania [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Property, Plant and Equipment, Net:	22,490				14,212				22,490	14,212	13,369
Europe [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Property, Plant and Equipment, Net:	18,910				18,758				18,910	18,758	14,300
Argentina [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Property, Plant and Equipment, Net:	8,071				8,714				8,071	8,714	9,427
Asia [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Property, Plant and Equipment, Net:	$ 9,318				$ 9,839				$ 9,318	$ 9,839	$ 6,897