Derivative Instruments - Oil and Natural-Gas Production/Processing Derivative Activities Table (Detail) (Not Designated as Hedging Instrument [Member], Price Risk Derivative [Member])	3 Months Ended
	Mar. 31, 2014
Three-Way Collars Natural Gas 2014 [Member]
Derivative [Line Items]
Derivative nonmonetary notional amount per day	600,000
Three Way Collars Natural Gas 2015 [Member]
Derivative [Line Items]
Derivative nonmonetary notional amount per day	635,000
Fixed-Price Contracts Natural Gas 2014 [Member]
Derivative [Line Items]
Derivative nonmonetary notional amount per day	600,000
Average price per MMBtu or barrel
Average price per MMBtu or barrel	4.26
Extendable Fixed-Price Contracts Natural Gas April 2014 to June 2014 [Member]
Derivative [Line Items]
Derivative nonmonetary notional amount per day	400,000	[1]
Average price per MMBtu or barrel
Average price per MMBtu or barrel	4.19
Fixed-Price Contracts Crude Oil 2014 [Member]
Derivative [Line Items]
Derivative nonmonetary notional amount per day	107
Average price per MMBtu or barrel
Average price per MMBtu or barrel	100.58
Call Option [Member] | Short [Member] | Three-Way Collars Natural Gas 2014 [Member]
Average price per MMBtu or barrel
Average ceiling price	5.01
Call Option [Member] | Short [Member] | Three Way Collars Natural Gas 2015 [Member]
Average price per MMBtu or barrel
Average ceiling price	4.76
Put Option [Member] | Short [Member] | Three-Way Collars Natural Gas 2014 [Member]
Average price per MMBtu or barrel
Average floor price	2.75
Put Option [Member] | Short [Member] | Three Way Collars Natural Gas 2015 [Member]
Average price per MMBtu or barrel
Average floor price	2.75
Put Option [Member] | Long [Member] | Three-Way Collars Natural Gas 2014 [Member]
Average price per MMBtu or barrel
Average floor price	3.75
Put Option [Member] | Long [Member] | Three Way Collars Natural Gas 2015 [Member]
Average price per MMBtu or barrel
Average floor price	3.75

[1] The extendable fixed-price contracts have a remaining contract term of April 2014 to June 2014 with an option to extend the contract term to December 2014 at the same price.