Commitments and Contingencies - Additional Information (Detail) (USD $)	9 Months Ended
	Sep. 30, 2013 Plaintiff Cases site	Dec. 31, 2012
Commitments And Contingent Liabilities [Line Items]
Number of cases administratively dismissed or inactive	100
Liable periods	20 years
Accrued environmental obligations approximately	$ 58,013,000	$ 48,006,000
Sites associated with remediation	50
Remediation and related matters possible to estimate costs	$ 154,000,000
Currently not able to estimate a range of costs to sites	5
Number of cases pending	1,130
Number of Plaintiffs Involved in Pending Cases	1,643
Other Litigation
Commitments And Contingent Liabilities [Line Items]
Number of cases administratively dismissed or inactive	8,298