Commitments and Contingencies - Additional Information (Detail) (USD $)	1 Months Ended	3 Months Ended		9 Months Ended			9 Months Ended		1 Months Ended	9 Months Ended	0 Months Ended
	Sep. 30, 2003 Parties	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	Dec. 31, 2013	Sep. 30, 2014 New Jersey MTBE Claim Against the Company, Marketing and Lukoil [Member]	Sep. 30, 2014 New Jersey MTBE Claim Against the Company [Member]	May 31, 2007 NJ MTBE [Member] Defendant	Sep. 30, 2014 NJ MTBE [Member] Defendant	Jun. 19, 2014 Pennsylvania MTBE [Member] Minimum [Member] Defendant
Loss Contingencies [Line Items]
Accrued legal matters		$ 11,040,000		$ 11,040,000		$ 11,423,000
Provisions for litigation losses		95,000	5,065,000	130,000	5,471,000
Number of potentially responsible parties for Lower Passaic River damages	66
Parties to perform a remedial investigation and feasibility study									70
Number of defendants in the MTBE complaint										50	50
Settlement amounts sought by the plaintiffs							$ 88,000,000	$ 24,000,000