CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS (UNAUDITED) (in thousands, except per share amounts) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended				6 Months Ended
	Jun. 30, 2014		Jun. 30, 2013		Jun. 30, 2014		Jun. 30, 2013
Operating revenues:
Oil, gas, and NGL production revenue	$ 654,661		$ 534,520		$ 1,277,770		$ 1,004,095
Other operating revenues	20,319		24,840		29,930		39,445
Total operating revenues	674,980		559,360		1,307,700		1,043,540
Operating expenses:
Oil, gas, and NGL production expense	177,598		149,737		341,307		275,370
Depletion, depreciation, amortization, and asset retirement obligation liability accretion	187,781		225,731		364,996		424,440
Exploration	24,270		20,657		45,605		36,055
Impairment of proved properties	0		34,552		0		55,771
Abandonment and impairment of unproved properties	164		4,339		2,965		4,641
General and administrative	38,115		35,374		73,166		67,654
Change in Net Profits Plan liability	(7,105)		(5,438)		(8,881)		(7,363)
Derivative loss (gain)	126,469	[1]	(85,190)	[1]	224,131	[1]	(54,618)	[1]
Other operating expenses	5,972		35,314		14,061		51,108
Total operating expenses	553,264		415,076		1,057,350		853,058
Income from operations	121,716		144,284		250,350		190,482
Non-operating income (expense)
Other, net	(1,847)		24		(1,821)		36
Interest expense	(24,040)		(21,581)		(48,230)		(40,682)
Income before income taxes	95,829		122,727		200,299		149,836
Income tax expense	(36,049)		(46,205)		(74,912)		(56,587)
Net income	$ 59,780		$ 76,522		$ 125,387		$ 93,249
Basic weighted-average common shares outstanding	67,069		66,295		67,063		66,254
Diluted weighted-average common shares outstanding	68,239		67,893		68,180		67,711
Basic net income per common share	$ 0.89		$ 1.15		$ 1.87		$ 1.41
Diluted net income per common share	$ 0.88		$ 1.13		$ 1.84		$ 1.38
Dividends per common share	$ 0.00		$ 0.00		$ 0.05		$ 0.05

[1] (2) Total derivative loss (gain) is reported in the derivative loss (gain) line item on the condensed consolidated statements of cash flows within cash provided by operating activities.