CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Revenues and other income:
Oil and gas revenue	$ 446,696	$ 855,877	$ 851,212
Gain on sale of assets	24,651	23,769
Other income	209	3,092	941
Total revenues and other income	471,556	882,738	852,153
Costs and expenses:
Oil and gas production	105,336	100,122	96,791
Exploration expenses	156,203	93,519	230,314
General and administrative	136,809	135,231	158,421
Depletion and depreciation	155,966	198,080	222,544
Interest and other financing costs, net	37,209	45,548	47,590
Derivatives, net	(210,649)	(281,853)	17,027
Restructuring charges		11,742
Other expenses, net	5,246	2,081	3,512
Total costs and expenses	386,120	304,470	776,199
Income before income taxes	85,436	578,268	75,954
Income tax expense	155,272	298,898	166,998
Net income (loss)	$ (69,836)	$ 279,370	$ (91,044)
Net income (loss) per share:
Basic (in dollars per share)	$ (0.18)	$ 0.73	$ (0.24)
Diluted (in dollars per share)	$ (0.18)	$ 0.72	$ (0.24)
Weighted average number of shares used to compute net income (loss) per share:
Basic (in shares)	382,610	379,195	376,819
Diluted (in shares)	382,610	386,119	376,819