Quarterly report pursuant to Section 13 or 15(d)

Condensed Consolidating Statement of Income (Detail)

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Condensed Consolidating Statement of Income (Detail) (USD $)
In Thousands, unless otherwise specified
 3 Months Ended
Mar. 31, 2013
Mar. 31, 2012
Condensed Financial Statements, Captions [Line Items]    
Revenues $ 259,222 $ 235,886
Operating costs and expenses:    
Lease operating expenses 59,341 56,663
Production taxes 1,789 1,485
Gathering and transportation 4,444 4,221
Depreciation, depletion, amortization and accretion 108,872 88,491
General and administrative expenses 21,087 29,479
Derivative loss 3,368 39,634
Total costs and expenses 198,901 219,973
Operating income 60,321 15,913
Earnings of affiliates      
Interest expense:    
Incurred 21,234 13,905
Capitalized (2,433) (3,191)
Income (loss) before income tax expense 41,520 5,199
Income tax expense 14,902 1,981
Net income 26,618 3,218
Parent Company
    
Condensed Financial Statements, Captions [Line Items]    
Revenues 209,528 176,562
Operating costs and expenses:    
Lease operating expenses 54,529 50,018
Production taxes 1,789 1,485
Gathering and transportation 3,662 3,484
Depreciation, depletion, amortization and accretion 86,416 67,623
General and administrative expenses 19,604 26,887
Derivative loss 3,368 39,634
Total costs and expenses 169,368 189,131
Operating income 40,160 (12,569)
Earnings of affiliates 13,100 18,516
Interest expense:    
Incurred 21,234 13,905
Capitalized (2,433) (3,191)
Income (loss) before income tax expense 34,459 (4,767)
Income tax expense 7,841 (7,985)
Net income 26,618 3,218
Guarantor Subsidiaries
    
Condensed Financial Statements, Captions [Line Items]    
Revenues 49,694 59,324
Operating costs and expenses:    
Lease operating expenses 4,812 6,645
Gathering and transportation 782 737
Depreciation, depletion, amortization and accretion 22,456 20,868
General and administrative expenses 1,483 2,592
Derivative loss      
Total costs and expenses 29,533 30,842
Operating income 20,161 28,482
Earnings of affiliates      
Interest expense:    
Income (loss) before income tax expense 20,161 28,482
Income tax expense 7,061 9,966
Net income 13,100 18,516
Eliminations
    
Operating costs and expenses:    
Depreciation, depletion, amortization and accretion      
Derivative loss      
Earnings of affiliates (13,100) (18,516)
Interest expense:    
Income (loss) before income tax expense (13,100) (18,516)
Net income $ (13,100) $ (18,516)