Commitments and Contingencies - Additional Information (Detail) (USD $)	1 Months Ended	12 Months Ended
	May 31, 2007 Entity mi	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009 Entity	Jul. 18, 2012 Entity	May 25, 2012 Director
Commitments and Contingencies [Line Items]
Expenditures under the noncapital purchase commitments		$ 83,599,000	$ 89,407,000	$ 111,142,000
Commitments of minimum royalties under mineral leases		222,230,000
Expenditures for mineral royalties under mineral leases		46,007,000	45,690,000	43,111,000
Period of letters of credit		1 year
Letter of credit outstanding		57,302,000
Amount of bank credit facility		600,000,000
Line of credit, expiration date		Dec. 15, 2016
Cash transaction bonus payable		1,137,000	1,228,000	882,000
Unrecognized tax benefits		13,550,000	13,488,000	28,075,000	20,974,000
Payment to Illinois Department of Transportation (IDOT)		40,000,000
Settlement awarded		49,657,000
Number of Former Directors in Ireland's Lawsuit							2
Number of other parties sued in the Lower Passaic River Clean-Up					300
Number of other companies to perform a Remedial Investigation/ Feasibility Study related to the Lower Passaic River Clean-Up lawsuit	70
Number of miles of the River used in the Remedial Investigation/Feasibility Study	17
Range of estimated cost, minimum		900,000,000
Range of estimated cost, maximum		3,500,000,000
Number of Other Companies Entered in to Administrative Settlement Agreement and Order						69
Property Plant and Equipment
Commitments and Contingencies [Line Items]
Unconditional purchase obligations		3,880,000
Noncapital
Commitments and Contingencies [Line Items]
Unconditional purchase obligations		$ 50,582,000