Commitments and Contingencies - Additional Information (Detail) (USD $)	3 Months Ended		1 Months Ended	0 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	May 31, 2007 Defendant	Jun. 19, 2014 Defendant	Dec. 31, 2014	Sep. 30, 2003 Parties
Loss Contingencies [Line Items]
Accrued legal matters	$ 11,140,000				$ 11,040,000
Provisions for litigation losses	100,000	10,000
New Jersey MTBE Claim Against the Company, Marketing and Lukoil [Member]
Loss Contingencies [Line Items]
Settlement amounts sought by the plaintiffs	88,000,000
New Jersey MTBE Claim Against the Company [Member]
Loss Contingencies [Line Items]
Settlement amounts sought by the plaintiffs	$ 24,000,000
Lower Passaic River [Member]
Loss Contingencies [Line Items]
Number of potentially responsible parties for Lower Passaic River damages						66
Parties to perform a remedial investigation and feasibility study			70
New Jersey [Member] | MTBE [Member]
Loss Contingencies [Line Items]
Number of defendants in the MTBE complaint	50
Pennsylvania [Member] | MTBE [Member] | Minimum [Member]
Loss Contingencies [Line Items]
Number of defendants in the MTBE complaint				50