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Derivative Activities - Schedule of Additional Information Related to Master Netting Arrangements with Derivative Counterparties (Detail) (USD $)
In Thousands, unless otherwise specified
Jun. 30, 2014
Dec. 31, 2013
Derivative [Line Items]    
Gross Amounts of Recognized Assets $ 31,102 $ 33,360
Gross Amounts Offset in the Balance Sheet (20,879) (19,706)
Net Amounts of Assets Presented in the Balance Sheet 10,223 13,654
Gross Amounts of Recognized (Liabilities) (90,945) (45,929)
Gross Amounts Offset in the Balance Sheet 20,879 19,706
Net Amounts of (Liabilities) Presented in the Balance Sheet (70,066) (26,223)
Natural gas | Swaps
    
Derivative [Line Items]    
Gross Amounts of Recognized Assets 4,967 4,240
Gross Amounts Offset in the Balance Sheet (1,606) (1,218)
Net Amounts of Assets Presented in the Balance Sheet 3,361 3,022
Gross Amounts of Recognized (Liabilities) (19,095) (4,790)
Gross Amounts Offset in the Balance Sheet 1,606 1,218
Net Amounts of (Liabilities) Presented in the Balance Sheet (17,489) (3,572)
Natural gas | Collars
    
Derivative [Line Items]    
Gross Amounts of Recognized Assets 3,594 16,057
Gross Amounts Offset in the Balance Sheet (3,826) (7,671)
Net Amounts of Assets Presented in the Balance Sheet (232) 8,386
Gross Amounts of Recognized (Liabilities) (15,750) (13,345)
Gross Amounts Offset in the Balance Sheet 3,826 7,671
Net Amounts of (Liabilities) Presented in the Balance Sheet (11,924) (5,674)
Natural gas | Basis Swaps
    
Derivative [Line Items]    
Gross Amounts of Recognized Assets 19,606 7,686
Gross Amounts Offset in the Balance Sheet (9,559) (7,686)
Net Amounts of Assets Presented in the Balance Sheet 10,047  
Gross Amounts of Recognized (Liabilities) (10,934) (3,756)
Gross Amounts Offset in the Balance Sheet 9,559 7,686
Net Amounts of (Liabilities) Presented in the Balance Sheet (1,375) 3,930
Crude oil | Swaps
    
Derivative [Line Items]    
Gross Amounts of Recognized Assets 84 3,567
Gross Amounts Offset in the Balance Sheet (2,305) (1,321)
Net Amounts of Assets Presented in the Balance Sheet (2,221) 2,246
Gross Amounts of Recognized (Liabilities) (36,628) (4,711)
Gross Amounts Offset in the Balance Sheet 2,305 1,321
Net Amounts of (Liabilities) Presented in the Balance Sheet (34,323) (3,390)
Crude oil | Collars
    
Derivative [Line Items]    
Gross Amounts of Recognized (Liabilities) (1,693) (398)
Net Amounts of (Liabilities) Presented in the Balance Sheet (1,693) (398)
Swap NGLs (Natural Gasoline) | C3 swaps
    
Derivative [Line Items]    
Gross Amounts of Recognized Assets 1,538 826
Gross Amounts Offset in the Balance Sheet (2,160) (826)
Net Amounts of Assets Presented in the Balance Sheet (622)  
Gross Amounts of Recognized (Liabilities) (6,246) (18,172)
Gross Amounts Offset in the Balance Sheet 2,160 826
Net Amounts of (Liabilities) Presented in the Balance Sheet (4,086) (17,346)
Swap NGLs (Natural Gasoline) | NC4 swaps
    
Derivative [Line Items]    
Gross Amounts of Recognized Assets 1,227 863
Gross Amounts Offset in the Balance Sheet (1,227) (863)
Gross Amounts of Recognized (Liabilities) (120) (757)
Gross Amounts Offset in the Balance Sheet 1,227 863
Net Amounts of (Liabilities) Presented in the Balance Sheet 1,107 106
Swap NGLs (Natural Gasoline) | C5 swaps
    
Derivative [Line Items]    
Gross Amounts of Recognized Assets 86 121
Gross Amounts Offset in the Balance Sheet (196) (121)
Net Amounts of Assets Presented in the Balance Sheet (110)  
Gross Amounts of Recognized (Liabilities) (479)  
Gross Amounts Offset in the Balance Sheet 196 121
Net Amounts of (Liabilities) Presented in the Balance Sheet $ (283) $ 121