Commodity Derivative Positions (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended	6 Months Ended
	Jun. 30, 2014 bbl	Jun. 30, 2014 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	3,277	3,277
Crude Oil | Group One
Derivative Instruments Related to Oil and Gas Production [Line Items]
Term		Sep. 30, 2014
Instrument	Collars
Derivative, Nonmonetary Notional Amount	2,000	2,000
Weighted Average Price, Floor/Swap	90.00	90.00
Weighted Average Price, Ceiling	94,330.00	94,330.00
Fair Value Asset	0	0
Fair Value Liability	1,862	1,862
Crude Oil | Group Two
Derivative Instruments Related to Oil and Gas Production [Line Items]
Term		Mar. 31, 2016
Instrument	Swaps
Derivative, Nonmonetary Notional Amount	2,000	2,000
Derivative, Swap Type, Average Fixed Price	90.43	90.43
Fair Value Asset	0	0
Fair Value Liability	418	418
Crude Oil | Group Four
Derivative Instruments Related to Oil and Gas Production [Line Items]
Term		Dec. 31, 2014
Instrument	Collars
Derivative, Nonmonetary Notional Amount	2,000	2,000
Weighted Average Price, Floor/Swap	90.00	90.00
Weighted Average Price, Ceiling	94,330.00	94,330.00
Fair Value Asset	0	0
Fair Value Liability	1,487	1,487
Crude Oil | Group Five
Derivative Instruments Related to Oil and Gas Production [Line Items]
Term		Mar. 31, 2015
Instrument	Collars
Derivative, Nonmonetary Notional Amount	4,000	4,000
Weighted Average Price, Floor/Swap	87.50	87.50
Weighted Average Price, Ceiling	94,660.00	94,660.00
Fair Value Asset	0	0
Fair Value Liability	2,284	2,284
Crude Oil | Group Six
Derivative Instruments Related to Oil and Gas Production [Line Items]
Term		Jun. 30, 2015
Instrument	Collars
Derivative, Nonmonetary Notional Amount	4,000	4,000
Weighted Average Price, Floor/Swap	87.50	87.50
Weighted Average Price, Ceiling	94,660.00	94,660.00
Fair Value Asset	0	0
Fair Value Liability	1,741	1,741
Crude Oil | Group Seven
Derivative Instruments Related to Oil and Gas Production [Line Items]
Term		Mar. 31, 2015
Instrument	Swaps
Derivative, Nonmonetary Notional Amount	9,000	9,000
Derivative, Swap Type, Average Fixed Price	91.81	91.81
Fair Value Asset	0	0
Fair Value Liability	6,227	6,227
Crude Oil | Group Eight
Derivative Instruments Related to Oil and Gas Production [Line Items]
Term		Sep. 30, 2015
Instrument	Collars
Derivative, Nonmonetary Notional Amount	3,000	3,000
Weighted Average Price, Floor/Swap	86.67	86.67
Weighted Average Price, Ceiling	94,730.00	94,730.00
Fair Value Asset	0	0
Fair Value Liability	1,002	1,002
Crude Oil | Group Nine
Derivative Instruments Related to Oil and Gas Production [Line Items]
Term		Dec. 31, 2015
Instrument	Collars
Derivative, Nonmonetary Notional Amount	3,000	3,000
Weighted Average Price, Floor/Swap	86.67	86.67
Weighted Average Price, Ceiling	94,730.00	94,730.00
Fair Value Asset	0	0
Fair Value Liability	719	719
Crude Oil | Group Nine
Derivative Instruments Related to Oil and Gas Production [Line Items]
Term		Sep. 30, 2014
Instrument	Swaps
Derivative, Nonmonetary Notional Amount	10,000	10,000
Derivative, Swap Type, Average Fixed Price	93.21	93.21
Fair Value Asset	0	0
Fair Value Liability	10,250	10,250
Crude Oil | Group Ten
Derivative Instruments Related to Oil and Gas Production [Line Items]
Term		Mar. 31, 2015
Instrument	Swaptions
Derivative, Nonmonetary Notional Amount	1,000	1,000
Derivative, Average Price Risk Option Strike Price	88.00	88.00
Fair Value Asset	0	0
Fair Value Liability	896	896
Crude Oil | Group Eleven
Derivative Instruments Related to Oil and Gas Production [Line Items]
Term		Jun. 30, 2015
Instrument	Swaptions
Derivative, Nonmonetary Notional Amount	1,000	1,000
Derivative, Average Price Risk Option Strike Price	88.00	88.00
Fair Value Asset	0	0
Fair Value Liability	896	896
Crude Oil | Group Fourteen
Derivative Instruments Related to Oil and Gas Production [Line Items]
Term		Dec. 31, 2014
Instrument	Swaps
Derivative, Nonmonetary Notional Amount	11,000	11,000
Derivative, Swap Type, Average Fixed Price	93.45	93.45
Fair Value Asset	0	0
Fair Value Liability	8,489	8,489
Crude Oil | Group Twelve
Derivative Instruments Related to Oil and Gas Production [Line Items]
Term		Jun. 30, 2016
Instrument	Swaps
Derivative, Nonmonetary Notional Amount	2,000	2,000
Derivative, Swap Type, Average Fixed Price	90.43	90.43
Fair Value Asset	0	0
Fair Value Liability	218	218
Crude Oil | Group Fifteen
Derivative Instruments Related to Oil and Gas Production [Line Items]
Term		Sep. 30, 2015
Instrument	Swaptions
Derivative, Nonmonetary Notional Amount	1,000	1,000
Derivative, Average Price Risk Option Strike Price	88.00	88.00
Fair Value Asset	0	0
Fair Value Liability	896	896
Crude Oil | Group Sixteen
Derivative Instruments Related to Oil and Gas Production [Line Items]
Term		Dec. 31, 2015
Instrument	Swaptions
Derivative, Nonmonetary Notional Amount	1,000	1,000
Derivative, Average Price Risk Option Strike Price	88.00	88.00
Fair Value Asset	0	0
Fair Value Liability	895	895
Crude Oil | Group Seventeen
Derivative Instruments Related to Oil and Gas Production [Line Items]
Term		Sep. 30, 2016
Instrument	Swaps
Derivative, Nonmonetary Notional Amount	2,000	2,000
Derivative, Swap Type, Average Fixed Price	90.43	90.43
Fair Value Asset	0	0
Fair Value Liability	75	75
Crude Oil | Group Eighteen
Derivative Instruments Related to Oil and Gas Production [Line Items]
Term		Dec. 31, 2016
Instrument	Swaps
Derivative, Nonmonetary Notional Amount	2,000	2,000
Derivative, Swap Type, Average Fixed Price	90.43	90.43
Fair Value Asset	17	17
Fair Value Liability	0	0
Crude Oil | Group Nineteen
Derivative Instruments Related to Oil and Gas Production [Line Items]
Term		Jun. 30, 2015
Instrument	Swaps
Derivative, Nonmonetary Notional Amount	9,000	9,000
Derivative, Swap Type, Average Fixed Price	91.81	91.81
Fair Value Asset	0	0
Fair Value Liability	4,637	4,637
Crude Oil | Group Twenty Four
Derivative Instruments Related to Oil and Gas Production [Line Items]
Term		Sep. 30, 2015
Instrument	Swaps
Derivative, Nonmonetary Notional Amount	8,000	8,000
Derivative, Swap Type, Average Fixed Price	91.06	91.06
Fair Value Asset	0	0
Fair Value Liability	3,478	3,478
Crude Oil | Group Thirty-Two
Derivative Instruments Related to Oil and Gas Production [Line Items]
Term		Dec. 31, 2015
Instrument	Swaps
Derivative, Nonmonetary Notional Amount	8,000	8,000
Derivative, Swap Type, Average Fixed Price	91.06	91.06
Fair Value Asset	0	0
Fair Value Liability	2,615	2,615
Natural Gas | Group Three
Derivative Instruments Related to Oil and Gas Production [Line Items]
Term		Dec. 31, 2014
Instrument	Swaps
Average Volume Per Day (MMBtu)	5,000	5,000
Weighted Average Price, Floor/Swap	4.50	4.50
Fair Value Asset	10	10
Fair Value Liability	0	0
Natural Gas | Group Twenty-Eight
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	0	0
Fair Value Liability	455	455
Natural Gas | Group Thirty-One
Derivative Instruments Related to Oil and Gas Production [Line Items]
Term		Mar. 31, 2015
Instrument	Swaps
Average Volume Per Day (MMBtu)	5,000	5,000
Weighted Average Price, Floor/Swap	4.50	4.50
Fair Value Asset	0	0
Fair Value Liability	$ 16	$ 16