Commodity Derivative Positions (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended	9 Months Ended
	Sep. 30, 2013 bbl	Sep. 30, 2013 bbl
Settlements to be paid in subsequent period
Derivative Instruments Related to Oil and Gas Production [Line Items]
Fair Value Asset	$ 0	$ 0
Fair Value Liability	2,608	2,608
Crude Oil | Group One
Derivative Instruments Related to Oil and Gas Production [Line Items]
Instrument	Collars
Average Volume Per Day (barrels)	1,500	1,500
Weighted Average Price, Floor/Swap	93.33	93.33
Weighted Average Price, Ceiling	102.80	102.80
Fair Value Asset	112	112
Fair Value Liability	154	154
Crude Oil | Group Two
Derivative Instruments Related to Oil and Gas Production [Line Items]
Instrument	Collars
Average Volume Per Day (barrels)	1,500	1,500
Weighted Average Price, Floor/Swap	93.33	93.33
Weighted Average Price, Ceiling	102.80	102.80
Fair Value Asset	287	287
Fair Value Liability	67	67
Crude Oil | Group Four
Derivative Instruments Related to Oil and Gas Production [Line Items]
Term		Jun. 30, 2013
Crude Oil | Group Five
Derivative Instruments Related to Oil and Gas Production [Line Items]
Term		Sep. 30, 2013
Crude Oil | Group Six
Derivative Instruments Related to Oil and Gas Production [Line Items]
Term		Dec. 31, 2013
Instrument	Collars
Average Volume Per Day (barrels)	2,400	2,400
Weighted Average Price, Floor/Swap	91.04	91.04
Weighted Average Price, Ceiling	100.02	100.02
Fair Value Asset	0	0
Fair Value Liability	707	707
Crude Oil | Group Eight
Derivative Instruments Related to Oil and Gas Production [Line Items]
Term		Jun. 30, 2013
Crude Oil | Group Nine
Derivative Instruments Related to Oil and Gas Production [Line Items]
Term		Sep. 30, 2013
Crude Oil | Group Ten
Derivative Instruments Related to Oil and Gas Production [Line Items]
Term		Dec. 31, 2013
Instrument	Swaps
Average Volume Per Day (barrels)	7,000	7,000
Weighted Average Price, Floor/Swap	95.94	95.94
Fair Value Asset	224	224
Fair Value Liability	3,806	3,806
Crude Oil | Group Eleven
Derivative Instruments Related to Oil and Gas Production [Line Items]
Term		Mar. 31, 2014
Instrument	Swaps
Average Volume Per Day (barrels)	7,500	7,500
Weighted Average Price, Floor/Swap	93.86	93.86
Fair Value Asset	292	292
Fair Value Liability	3,580	3,580
Crude Oil | Group Twelve
Derivative Instruments Related to Oil and Gas Production [Line Items]
Term		Jun. 30, 2014
Instrument	Swaps
Average Volume Per Day (barrels)	7,500	7,500
Weighted Average Price, Floor/Swap	93.86	93.86
Fair Value Asset	767	767
Fair Value Liability	2,363	2,363
Crude Oil | Group Thirteen
Derivative Instruments Related to Oil and Gas Production [Line Items]
Term		Sep. 30, 2014
Instrument	Swaps
Average Volume Per Day (barrels)	8,000	8,000
Weighted Average Price, Floor/Swap	93.18	93.18
Fair Value Asset	1,041	1,041
Fair Value Liability	1,841	1,841
Crude Oil | Group Fourteen
Derivative Instruments Related to Oil and Gas Production [Line Items]
Term		Dec. 31, 2014
Instrument	Swaps
Average Volume Per Day (barrels)	8,000	8,000
Weighted Average Price, Floor/Swap	93.18	93.18
Fair Value Asset	1,434	1,434
Fair Value Liability	1,052	1,052
Crude Oil | Group Seven
Derivative Instruments Related to Oil and Gas Production [Line Items]
Instrument	Swaps
Average Volume Per Day (barrels)	2,000	2,000
Weighted Average Price, Floor/Swap	92.03	92.03
Fair Value Asset	192	192
Fair Value Liability	231	231
Crude Oil | Group Nineteen
Derivative Instruments Related to Oil and Gas Production [Line Items]
Instrument	Swaps
Average Volume Per Day (barrels)	2,000	2,000
Weighted Average Price, Floor/Swap	92.03	92.03
Fair Value Asset	518	518
Fair Value Liability	376	376
Crude Oil | Group Twenty Four
Derivative Instruments Related to Oil and Gas Production [Line Items]
Instrument	Swaps
Average Volume Per Day (barrels)	1,000	1,000
Weighted Average Price, Floor/Swap	91.25	91.25
Fair Value Asset	319	319
Fair Value Liability	236	236
Crude Oil | Group Thirty-Two [Member]
Derivative Instruments Related to Oil and Gas Production [Line Items]
Instrument	Swaps
Average Volume Per Day (barrels)	1,000	1,000
Weighted Average Price, Floor/Swap	91.25	91.25
Fair Value Asset	395	395
Fair Value Liability	254	254
Crude Oil | Group Fifteen
Derivative Instruments Related to Oil and Gas Production [Line Items]
Term		Mar. 31, 2014
Instrument	Swaption
Average Volume Per Day (barrels)	812	812
Weighted Average Price, Floor/Swap	100.00	100.00
Fair Value Asset	0	0
Fair Value Liability	111	111
Crude Oil | Group Sixteen
Derivative Instruments Related to Oil and Gas Production [Line Items]
Term		Jun. 30, 2014
Instrument	Swaption
Average Volume Per Day (barrels)	812	812
Weighted Average Price, Floor/Swap	100.00	100.00
Fair Value Asset	0	0
Fair Value Liability	111	111
Crude Oil | Group Seventeen
Derivative Instruments Related to Oil and Gas Production [Line Items]
Term		Sep. 30, 2014
Instrument	Swaption
Average Volume Per Day (barrels)	812	812
Weighted Average Price, Floor/Swap	100.00	100.00
Fair Value Asset	0	0
Fair Value Liability	112	112
Crude Oil | Group Eighteen
Derivative Instruments Related to Oil and Gas Production [Line Items]
Term		Dec. 31, 2014
Instrument	Swaption
Average Volume Per Day (barrels)	812	812
Weighted Average Price, Floor/Swap	100.00	100.00
Fair Value Asset	0	0
Fair Value Liability	112	112
Natural Gas
Derivative Instruments Related to Oil and Gas Production [Line Items]
Fair Value Liability	0	0
Natural Gas | Group Three
Derivative Instruments Related to Oil and Gas Production [Line Items]
Instrument	Swaps
Average Volume Per Day (MMBtu)	5,000	5,000
Weighted Average Price, Floor/Swap	4.50	4.50
Fair Value Asset	240	240
Natural Gas | Group Twenty
Derivative Instruments Related to Oil and Gas Production [Line Items]
Term		Jun. 30, 2013
Natural Gas | Group Twenty-One
Derivative Instruments Related to Oil and Gas Production [Line Items]
Term		Sep. 30, 2013
Natural Gas | Group Twenty-Two
Derivative Instruments Related to Oil and Gas Production [Line Items]
Term		Dec. 31, 2013
Instrument	Collars
Average Volume Per Day (MMBtu)	15,000	15,000
Weighted Average Price, Floor/Swap	3.67	3.67
Weighted Average Price, Ceiling	4.37	4.37
Fair Value Asset	242	242
Fair Value Liability	0	0
Natural Gas | Group Twenty-Three
Derivative Instruments Related to Oil and Gas Production [Line Items]
Term		Mar. 31, 2014
Instrument	Collars
Average Volume Per Day (MMBtu)	5,000	5,000
Weighted Average Price, Floor/Swap	4.00	4.00
Weighted Average Price, Ceiling	4.50	4.50
Fair Value Asset	131	131
Fair Value Liability	0	0
Natural Gas | Group Twenty-Five
Derivative Instruments Related to Oil and Gas Production [Line Items]
Term		Jun. 30, 2013
Natural Gas | Group Twenty-Six
Derivative Instruments Related to Oil and Gas Production [Line Items]
Term		Sep. 30, 2013
Natural Gas | Group Twenty-Seven
Derivative Instruments Related to Oil and Gas Production [Line Items]
Term		Dec. 31, 2013
Instrument	Swaps
Average Volume Per Day (MMBtu)	10,000	10,000
Weighted Average Price, Floor/Swap	4.04	4.04
Fair Value Asset	411	411
Fair Value Liability	0	0
Natural Gas | Group Twenty-Eight
Derivative Instruments Related to Oil and Gas Production [Line Items]
Term		Mar. 31, 2014
Instrument	Swaps
Average Volume Per Day (MMBtu)	10,000	10,000
Weighted Average Price, Floor/Swap	4.28	4.28
Fair Value Asset	407	407
Fair Value Liability	0	0
Natural Gas | Group Twenty-Nine
Derivative Instruments Related to Oil and Gas Production [Line Items]
Term		Jun. 30, 2014
Instrument	Swaps
Average Volume Per Day (MMBtu)	15,000	15,000
Weighted Average Price, Floor/Swap	4.10	4.10
Fair Value Asset	433	433
Fair Value Liability	0	0
Natural Gas | Group Thirty
Derivative Instruments Related to Oil and Gas Production [Line Items]
Term		Sep. 30, 2014
Instrument	Swaps
Average Volume Per Day (MMBtu)	15,000	15,000
Weighted Average Price, Floor/Swap	4.10	4.10
Fair Value Asset	344	344
Fair Value Liability	0	0
Natural Gas | Group Thirty-One
Derivative Instruments Related to Oil and Gas Production [Line Items]
Instrument	Swaps
Average Volume Per Day (MMBtu)	5,000	5,000
Weighted Average Price, Floor/Swap	4.50	4.50
Fair Value Asset	151	151
Fair Value Liability	$ 0	$ 0