Commitments - Additional Information (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended				12 Months Ended					1 Months Ended	12 Months Ended			1 Months Ended		12 Months Ended						1 Months Ended		12 Months Ended				12 Months Ended	1 Months Ended	12 Months Ended				1 Months Ended	12 Months Ended		1 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2012 Lease Agreements	Dec. 31, 2012 During 2013 Natural Gas Purchase Contract	Dec. 31, 2012 During 2014 Natural Gas Purchase Contract	Dec. 31, 2012 During 2015 Natural Gas Purchase Contract	Dec. 31, 2012 During 2016 Natural Gas Purchase Contract	Dec. 31, 2012 During 2017 Natural Gas Purchase Contract	Oct. 31, 2008 Bauxite raw materials Supplier 4	Dec. 31, 2012 Bauxite raw materials Supplier 4	Dec. 31, 2011 Bauxite raw materials Supplier 4	Dec. 31, 2010 Bauxite raw materials Supplier 4	Oct. 31, 2008 Bauxite raw materials Supplier 4 Within Three Years From Agreement Date T	Oct. 31, 2008 Bauxite raw materials Supplier 4 More Than Three Years From Agreement Date T	Dec. 31, 2010 Bauxite And Hard Clays Supplier 5 CHINA	Dec. 31, 2002 Bauxite And Hard Clays Supplier 5 CHINA	Dec. 31, 2011 Bauxite And Hard Clays Supplier 6 CHINA	Dec. 31, 2010 Bauxite And Hard Clays Supplier 6 CHINA	Dec. 31, 2002 Bauxite And Hard Clays Supplier 6 CHINA	Dec. 31, 2002 Bauxite And Hard Clays Supplier 6 Minimum CHINA	Nov. 01, 2008 McIntyre Wilkinson County Development Authority	Jan. 31, 2003 McIntyre kaolin Supplier 3	Dec. 31, 2012 McIntyre kaolin Supplier 3	Dec. 31, 2011 McIntyre kaolin Supplier 3	Dec. 31, 2010 McIntyre kaolin Supplier 3	Jan. 31, 2003 McIntyre kaolin Supplier 3 Minimum	Dec. 31, 2010 Eufaula kaolin Supplier 1	May 31, 2012 Eufaula kaolin Supplier 2	Dec. 31, 2012 Eufaula kaolin Supplier 2	Dec. 31, 2011 Eufaula kaolin Supplier 2	May 31, 2012 Eufaula kaolin Supplier 2 After Amendment	Dec. 31, 2011 Eufaula kaolin Supplier 2 Minimum	May 31, 2012 Eufaula kaolin Supplier 2 Minimum After Amendment	Dec. 31, 2012 Marshfield, Wisconsin	Dec. 31, 2011 Marshfield, Wisconsin	Jul. 31, 2011 Marshfield, Wisconsin Prior Agreement	Jan. 30, 2012 Marshfield, Wisconsin After Amendment	Jan. 30, 2012 Marshfield, Wisconsin During 2013 After Amendment T	Jan. 30, 2012 Marshfield, Wisconsin During 2014 After Amendment T	Jul. 31, 2011 Marshfield, Wisconsin During 2011 Prior Agreement T	Jul. 31, 2011 Marshfield, Wisconsin During 2012 Prior Agreement T	Jan. 30, 2012 Marshfield, Wisconsin During 2012 After Amendment T	Nov. 30, 2012 Millen Georgia Jenkins County Development Authority	May 31, 2012 Millen Georgia Kaolin And Bauxite Supplier 7	May 31, 2012 Millen Georgia Kaolin And Bauxite Supplier 7 Minimum
Long-term Purchase Commitment [Line Items]
Purchase commitment amount												$ 1,400	$ 1,400					$ 2,918	$ 2,834					$ 2,491	$ 2,900	$ 1,687		$ 3,603		$ 3,012	$ 3,205				$ 2,538	$ 462
Purchase commitment, period										10 years							5 years			10 years								7 years			3 years			5 years			5 years								5 years
Agreement expiration date																Dec. 31, 2010		Dec. 31, 2011										Dec. 31, 2010
Commitment effective date																							2003-01-01						May 2012		2011-01-01						2011-07-30
Additional purchase commitment, period										10 years							3 years														6 years	3 years													5 years
Purchase obligation percentage of annual requirements																					80.00%						80.00%						70.00%	50.00%												50.00%
Agreement entry date										Oct. 31, 2008												Nov. 01, 2008	Jan. 01, 2003																					Nov. 01, 2012	May 31, 2012
Minimum quantity to be purchased annually														40,000	70,000																								150,000	350,000	40,000	100,000	150,000
Purchase commiment coverage period															3 years
Agreement Termination Date											2012
Purchase commitment, commencing date																																						2012-01-30
Facility construction completion period																																													Construction of the facility is expected to be completed in early 2014.
Annual rental fee	21,452	11,590	9,054																			50
Lease agreement period																						Through the year 2022																						Until the tenth anniversary of completion of the final phase of the facility
Lease administrative fees																																												50
Net book value of property leased	426,232	392,659		251,602
Natural gas purchase commitment annually					$ 25,087	$ 18,679	$ 18,679	$ 11,619	$ 1,220