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		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Operating revenues:
Oil, gas, and NGL production revenue	$ 601,787	$ 373,928	$ 1,605,882	$ 1,049,131
Realized hedge gain (loss)	(489)	501	(1,777)	2,338
Loss on divestiture activity	(6,216)	(8,532)	(510)	(31,246)
Other operating revenues	18,025	13,054	53,052	40,571
Total operating revenues	613,107	378,951	1,656,647	1,060,794
Operating expenses:
Oil, gas, and NGL production expense	158,921	102,447	434,291	280,713
Depletion, depreciation, amortization, and asset retirement obligation liability accretion	195,792	192,432	620,232	523,610
Exploration	16,280	25,417	52,335	66,031
Impairment of proved properties	5,935	0	61,706	38,523
Abandonment and impairment of unproved properties	3,818	447	8,459	11,296
General and administrative	33,920	32,171	101,574	91,443
Change in Net Profits Plan liability	940	798	(6,423)	(17,342)
Derivative (gain) loss	39,933	55,856	(14,685)	(40,040)
Other operating expenses	20,084	12,219	71,192	40,780
Total operating expenses	475,623	421,787	1,328,681	995,014
Income (loss) from operations	137,484	(42,836)	327,966	65,780
Non-operating income (expense)
Interest income	28	126	64	201
Interest expense	(24,488)	(18,362)	(65,170)	(45,352)
Income (loss) before income taxes	113,024	(61,072)	262,860	20,629
Income tax (expense) benefit	(42,334)	22,736	(98,921)	(7,740)
Net income (loss)	$ 70,690	$ (38,336)	$ 163,939	$ 12,889
Basic weighted-average common shares outstanding	66,943	65,745	66,486	64,815
Diluted weighted-average common shares outstanding	68,253	65,745	67,969	67,343
Basic net income (loss) per common share	$ 1.06	$ (0.58)	$ 2.47	$ 0.20
Diluted net income (loss) per common share	$ 1.04	$ (0.58)	$ 2.41	$ 0.19
Dividends per common share	$ 0.05	$ 0.05	$ 0.10	$ 0.10