Derivative Financial Instruments - Derivative Financial Instruments (Detail) (Derivatives Designated as Hedges [Member], USD $) In Thousands, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Derivative [Line Items]
Asset derivatives fair value	$ 329	$ 13,288
Liability derivatives fair value	30,767	42,055
Accounts receivable-other [Member]
Derivative [Line Items]
Asset derivatives fair value	328	11,641
Accounts payable [Member]
Derivative [Line Items]
Liability derivatives fair value	15,283	20,209
Other assets [Member]
Derivative [Line Items]
Asset derivatives fair value	1	1,647
Other liabilities [Member]
Derivative [Line Items]
Liability derivatives fair value	$ 15,484	$ 21,846