Consolidated statements of operations (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Revenues:
Commodity sales	$ 681,557	$ 591,674	$ 509,503
Gain from oil hedging activities	0	37,134	46,746
Total revenues	681,557	628,808	556,249
Costs and expenses:
Lease operating	149,903	139,771	130,960
Production taxes	28,305	33,266	32,003
Depreciation, depletion & amortization	245,908	192,426	169,307
Loss on impairment of other assets	0	3,490	2,000
General and administrative	53,414	53,883	49,812
Total costs and expenses	477,530	422,836	384,082
Operating income	204,027	205,972	172,167
Non-operating income (expense):
Interest expense	(104,241)	(96,876)	(98,402)
Non-hedge derivative (losses) gains	231,320	(21,635)	49,685
Loss on extinguishment of debt	0	0	(21,714)
Other income	2,630	1,075	504
Net non-operating expense	129,709	(117,436)	(69,927)
Income before income taxes	333,736	88,536	102,240
Income tax expense	124,443	32,849	37,837
Net income	$ 209,293	$ 55,687	$ 64,403