Condensed Consolidated Balance Sheets (USD $) In Thousands, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Current assets
Cash	$ 248,325	$ 89,103
Marketable Securities, Current	0	166,343
Cash, Cash Equivalents, and Short-term Investments	248,325	255,446
Accounts receivable - net of allowance for doubtful accounts	59,491	58,645
Derivative assets at fair value	66,098	57,523
Other current assets	22,386	22,346
Total current assets	396,300	393,960
Property, plant and equipment - net
Oil and gas properties, full cost method (including unevaluated costs of $218,398 and $221,605, respectively)	608,572	640,443
Property, Plant and Equipment, Other, Net	203,908	220,362
Property, plant and equipment, net of accumulated depletion and depreciation	812,480	860,805
Derivative assets at fair value	25,968	73,357
Other assets	33,509	41,604
Total assets	1,268,257	1,369,726
Current liabilities
Accounts payable	13,587	28,822
Accrued liabilities	94,091	102,850
Derivative liabilities at fair value	846	3,125
Total current liabilities	108,524	134,797
Long-term debt	2,037,844	1,988,946
Partnership liability	94,651	126,132
Asset retirement obligations	105,480	106,256
Derivative liabilities at fair value	0	323
Other liabilities	19,242	19,242
Commitments and contingencies (Note 7)
Stockholders' equity
Preferred stock, par value $0.01, 10,000,000 shares authorized, none outstanding	0	0
Common stock, $0.01 par value, 400,000,000 shares authorized, and 187,222,654 and 183,994,879 shares issued, respectively	1,872	1,840
Paid in capital in excess of par value	779,206	770,092
Treasury stock of 7,444,372 and 6,698,640 shares, respectively	(53,810)	(51,422)
Accumulated other comprehensive income	82,780	109,881
Retained deficit	(1,907,532)	(1,836,361)
Total stockholders' equity	(1,097,484)	(1,005,970)
Total liabilities and stockholders' equity	$ 1,268,257	$ 1,369,726