Commitments and Contingencies - Additional Information (Detail) (USD $)	3 Months Ended
	Mar. 31, 2015 Plaintiff Cases site	Dec. 31, 2014
Loss Contingencies [Line Items]
Number of cases administratively dismissed or inactive	100
Liable periods	twenty-year
Litigation settlement amount	$ 1,150,000,000
Accrued environmental obligations approximately	109,835,000	110,015,000
Sites associated with remediation	47
Remediation and related matters possible to estimate costs	$ 149,000,000
Currently not able to estimate a range of costs to sites	5
Number of cases pending	166
Number of Plaintiffs Involved in Pending Cases	712
Other Litigation
Loss Contingencies [Line Items]
Number of cases administratively dismissed or inactive	8,692