Guarantees and Contingencies - Additional Information (Detail) - USD ($) $ in Millions	6 Months Ended	12 Months Ended
	Jun. 30, 2015	Dec. 31, 2014
Loss Contingencies [Line Items]
Settlements amount paid by HOVENSA		$ 3.5
VIRGIN ISLANDS, US
Loss Contingencies [Line Items]
Agreement to pay government of the U.S. Virgin Islands	$ 40.0
HOVENSA LLC.
Loss Contingencies [Line Items]
Interest in Joint Venture	50%