Fair Value Measurements - Schedule of Valuation Process and Unobservable Inputs (Detail) (Level 3 [Member], USD $) | 9 Months Ended |
In Thousands, unless otherwise specified | Sep. 30, 2014 |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items] | ' |
Fair Value, Derivative Asset (Liability) | $21,630 |
Bbl [Member] | Derivative Financial Instruments, Assets | Crude Oil [Member] | Swap [Member] | ' |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items] | ' |
Fair Value, Derivative Asset (Liability) | 12,042 |
Derivative assets, Valuation Technique | 'Discounted cash flow |
Unobservable Input | 'Forward price curve-swaps |
Bbl [Member] | Derivative Financial Instruments, Assets | Crude Oil [Member] | Costless Collar [Member] | ' |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items] | ' |
Fair Value, Derivative Asset (Liability) | 161 |
Derivative assets, Valuation Technique | 'Option model |
Unobservable Input | 'Forward price curve-costless collar option value |
MMBtu [Member] | Derivative Liabilities [Member] | NGL [Member] | Swap [Member] | ' |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items] | ' |
Fair Value, Derivative Asset (Liability) | -132 |
Derivative assets, Valuation Technique | 'Discounted cash flow |
Unobservable Input | 'Forward price curve-swaps |
MMBtu [Member] | Derivative Liabilities [Member] | Natural Gas [Member] | Natural Gas Swaps [Member] | ' |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items] | ' |
Fair Value, Derivative Asset (Liability) | -1,120 |
Derivative assets, Valuation Technique | 'Discounted cash flow |
Unobservable Input | 'Forward price curve-swaps |
MMBtu [Member] | Derivative Financial Instruments, Assets | NGL [Member] | Swap [Member] | ' |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items] | ' |
Fair Value, Derivative Asset (Liability) | 5,006 |
Derivative assets, Valuation Technique | 'Discounted cash flow |
Unobservable Input | 'Forward price curve-swaps |
MMBtu [Member] | Derivative Financial Instruments, Assets | Natural Gas [Member] | Costless Collar [Member] | ' |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items] | ' |
Fair Value, Derivative Asset (Liability) | 3,220 |
Derivative assets, Valuation Technique | 'Option model |
Unobservable Input | 'Forward price curve-costless collar option value |
MMBtu [Member] | Derivative Financial Instruments, Assets | Natural Gas [Member] | Natural Gas Swaps [Member] | ' |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items] | ' |
Fair Value, Derivative Asset (Liability) | $2,453 |
Derivative assets, Valuation Technique | 'Discounted cash flow |
Unobservable Input | 'Forward price curve-swaps |
Minimum [Member] | Bbl [Member] | Derivative Financial Instruments, Assets | Crude Oil [Member] | Swap [Member] | ' |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items] | ' |
Forward Price Curve | 85.3 |
Minimum [Member] | Bbl [Member] | Derivative Financial Instruments, Assets | Crude Oil [Member] | Costless Collar [Member] | ' |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items] | ' |
Forward Price Curve | -0.12 |
Minimum [Member] | MMBtu [Member] | Derivative Liabilities [Member] | NGL [Member] | Swap [Member] | ' |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items] | ' |
Forward Price Curve | 1.83 |
Minimum [Member] | MMBtu [Member] | Derivative Liabilities [Member] | Natural Gas [Member] | Natural Gas Swaps [Member] | ' |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items] | ' |
Forward Price Curve | 4.01 |
Minimum [Member] | MMBtu [Member] | Derivative Financial Instruments, Assets | NGL [Member] | Swap [Member] | ' |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items] | ' |
Forward Price Curve | 0.24 |
Minimum [Member] | MMBtu [Member] | Derivative Financial Instruments, Assets | Natural Gas [Member] | Costless Collar [Member] | ' |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items] | ' |
Forward Price Curve | -0.22 |
Minimum [Member] | MMBtu [Member] | Derivative Financial Instruments, Assets | Natural Gas [Member] | Natural Gas Swaps [Member] | ' |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items] | ' |
Forward Price Curve | -0.02 |
Maximum [Member] | Bbl [Member] | Derivative Financial Instruments, Assets | Crude Oil [Member] | Swap [Member] | ' |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items] | ' |
Forward Price Curve | 92.73 |
Maximum [Member] | Bbl [Member] | Derivative Financial Instruments, Assets | Crude Oil [Member] | Costless Collar [Member] | ' |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items] | ' |
Forward Price Curve | 1.4 |
Maximum [Member] | MMBtu [Member] | Derivative Liabilities [Member] | NGL [Member] | Swap [Member] | ' |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items] | ' |
Forward Price Curve | 1.93 |
Maximum [Member] | MMBtu [Member] | Derivative Liabilities [Member] | Natural Gas [Member] | Natural Gas Swaps [Member] | ' |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items] | ' |
Forward Price Curve | 4.35 |
Maximum [Member] | MMBtu [Member] | Derivative Financial Instruments, Assets | NGL [Member] | Swap [Member] | ' |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items] | ' |
Forward Price Curve | 1.95 |
Maximum [Member] | MMBtu [Member] | Derivative Financial Instruments, Assets | Natural Gas [Member] | Costless Collar [Member] | ' |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items] | ' |
Forward Price Curve | 0.37 |
Maximum [Member] | MMBtu [Member] | Derivative Financial Instruments, Assets | Natural Gas [Member] | Natural Gas Swaps [Member] | ' |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items] | ' |
Forward Price Curve | 4.35 |
Weighted Average [Member] | Bbl [Member] | Derivative Financial Instruments, Assets | Crude Oil [Member] | Swap [Member] | ' |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items] | ' |
Forward Price Curve | 88.51 |
Weighted Average [Member] | Bbl [Member] | Derivative Financial Instruments, Assets | Crude Oil [Member] | Costless Collar [Member] | ' |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items] | ' |
Forward Price Curve | -0.58 |
Weighted Average [Member] | MMBtu [Member] | Derivative Liabilities [Member] | NGL [Member] | Swap [Member] | ' |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items] | ' |
Forward Price Curve | 1.87 |
Weighted Average [Member] | MMBtu [Member] | Derivative Liabilities [Member] | Natural Gas [Member] | Natural Gas Swaps [Member] | ' |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items] | ' |
Forward Price Curve | 4.15 |
Weighted Average [Member] | MMBtu [Member] | Derivative Financial Instruments, Assets | NGL [Member] | Swap [Member] | ' |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items] | ' |
Forward Price Curve | 0.76 |
Weighted Average [Member] | MMBtu [Member] | Derivative Financial Instruments, Assets | Natural Gas [Member] | Costless Collar [Member] | ' |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items] | ' |
Forward Price Curve | -0.09 |
Weighted Average [Member] | MMBtu [Member] | Derivative Financial Instruments, Assets | Natural Gas [Member] | Natural Gas Swaps [Member] | ' |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items] | ' |
Forward Price Curve | 4.05 |