Impact of Rights of Offset Associated with Recognized Assets and Liabilities (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013
Current Asset [Member]
Derivative Instruments And Hedging Activities [Line Items]
Fair Value of Derivative Instruments, Assets	$ 4,549
Long-term assets [Member]
Derivative Instruments And Hedging Activities [Line Items]
Fair Value of Derivative Instruments, Assets	1,378
Current liabilities [Member]
Derivative Instruments And Hedging Activities [Line Items]
Fair Value of Derivative Instruments, Liabilities	(7,753)
Long-term liabilities [Member]
Derivative Instruments And Hedging Activities [Line Items]
Fair Value of Derivative Instruments, Liabilities	(470)
Effects of Netting [Member] | Current Asset [Member]
Derivative Instruments And Hedging Activities [Line Items]
Fair Value of Derivative Instruments, Assets	(4,043)
Effects of Netting [Member] | Long-term assets [Member]
Derivative Instruments And Hedging Activities [Line Items]
Fair Value of Derivative Instruments, Assets	(274)
Effects of Netting [Member] | Current liabilities [Member]
Derivative Instruments And Hedging Activities [Line Items]
Fair Value of Derivative Instruments, Liabilities	4,043
Effects of Netting [Member] | Long-term liabilities [Member]
Derivative Instruments And Hedging Activities [Line Items]
Fair Value of Derivative Instruments, Liabilities	274
With Effects of Netting [Member] | Current Asset [Member]
Derivative Instruments And Hedging Activities [Line Items]
Fair Value of Derivative Instruments, Assets	506
With Effects of Netting [Member] | Long-term assets [Member]
Derivative Instruments And Hedging Activities [Line Items]
Fair Value of Derivative Instruments, Assets	1,104
With Effects of Netting [Member] | Current liabilities [Member]
Derivative Instruments And Hedging Activities [Line Items]
Fair Value of Derivative Instruments, Liabilities	(3,710)
With Effects of Netting [Member] | Long-term liabilities [Member]
Derivative Instruments And Hedging Activities [Line Items]
Fair Value of Derivative Instruments, Liabilities	$ (196)