Financial Instruments - Effect of Derivative Instruments on Condensed Consolidated Balance Sheets (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Derivatives, Fair Value [Line Items]
Derivative assets	$ 137	$ 1,423
Derivative liabilities	(7,052)	(2,288)
Total derivative instruments	(6,915)	(865)
Derivatives Designated as Cash-Flow Hedging Instruments [Member] | Interest Rate Swap [Member] | Other Assets [Member]
Derivatives, Fair Value [Line Items]
Derivative assets	42	86
Derivatives Designated as Cash-Flow Hedging Instruments [Member] | Interest Rate Swap [Member] | Derivative Liability Short-Term [Member]
Derivatives, Fair Value [Line Items]
Derivative liabilities	(268)	(209)
Derivatives Designated as Cash-Flow Hedging Instruments [Member] | Interest Rate Swap [Member] | Derivative Liability Long-Term [Member]
Derivatives, Fair Value [Line Items]
Derivative liabilities	(17)	(69)
Derivatives Not Designated as Cash-Flow Hedging Instruments [Member] | Crude Oil Commodity Contracts [Member] | Other Assets [Member]
Derivatives, Fair Value [Line Items]
Derivative assets	13	980
Derivatives Not Designated as Cash-Flow Hedging Instruments [Member] | Crude Oil Commodity Contracts [Member] | Other Current Assets [Member]
Derivatives, Fair Value [Line Items]
Derivative assets		307
Derivatives Not Designated as Cash-Flow Hedging Instruments [Member] | Crude Oil Commodity Contracts [Member] | Derivative Liability Short-Term [Member]
Derivatives, Fair Value [Line Items]
Derivative liabilities	(4,640)	(1,667)
Derivatives Not Designated as Cash-Flow Hedging Instruments [Member] | Crude Oil Commodity Contracts [Member] | Derivative Liability Long-Term [Member]
Derivatives, Fair Value [Line Items]
Derivative liabilities	(1,460)	(25)
Derivatives Not Designated as Cash-Flow Hedging Instruments [Member] | Natural Gas Commodity Contracts [Member] | Other Assets [Member]
Derivatives, Fair Value [Line Items]
Derivative assets	37
Derivatives Not Designated as Cash-Flow Hedging Instruments [Member] | Natural Gas Commodity Contracts [Member] | Other Current Assets [Member]
Derivatives, Fair Value [Line Items]
Derivative assets	45	50
Derivatives Not Designated as Cash-Flow Hedging Instruments [Member] | Natural Gas Commodity Contracts [Member] | Derivative Liability Short-Term [Member]
Derivatives, Fair Value [Line Items]
Derivative liabilities	(640)	(318)
Derivatives Not Designated as Cash-Flow Hedging Instruments [Member] | Natural Gas Commodity Contracts [Member] | Derivative Liability Long-Term [Member]
Derivatives, Fair Value [Line Items]
Derivative liabilities	$ (27)