Guarantees and Contingencies - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	1 Months Ended	12 Months Ended
	Mar. 31, 2014	Dec. 31, 2014
Loss Contingencies [Line Items]
Contingent liability associated with letters of credit		$ 54
Settlements amount paid by HOVENSA		3.5
Litigation settlement for MTBE	35
VIRGIN ISLANDS, US
Loss Contingencies [Line Items]
Agreement to pay government of the U.S. Virgin Islands		$ 40