Condensed Consolidated Balance Sheets (USD $) In Thousands, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Current assets
Cash	$ 22,284	$ 89,103
Marketable Securities, Current	9,987	166,343
Cash, Cash Equivalents, and Short-term Investments	32,271	255,446
Accounts receivable - net of allowance for doubtful accounts	69,556	58,645
Derivative assets at fair value	48,454	57,523
Other current assets	29,835	22,346
Total current assets	180,116	393,960
Property, plant and equipment - net
Oil and gas properties, full cost method (including unevaluated costs of $230,719 and $221,605, respectively)	601,657	640,443
Property, Plant and Equipment, Other, Net	213,674	220,362
Property, plant and equipment, net of accumulated depletion and depreciation	815,331	860,805
Derivative assets at fair value	28,037	73,357
Other assets	35,563	41,604
Total assets	1,059,047	1,369,726
Current liabilities
Accounts payable	13,985	28,822
Accrued liabilities	119,999	102,850
Derivative liabilities at fair value	5,965	3,125
Total current liabilities	139,949	134,797
Long-term debt	1,795,644	1,988,946
Partnership liability	99,083	126,132
Asset retirement obligations	107,324	106,256
Derivative liabilities at fair value	7,721	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 184,764,736 and 183,994,879 shares issued, respectively	1,848	1,840
Paid in capital in excess of par value	775,661	770,092
Treasury stock of 7,441,757 and 6,698,640 shares, respectively	(53,805)	(51,422)
Accumulated other comprehensive income	97,669	109,881
Retained deficit	(1,931,289)	(1,836,361)
Total stockholders' equity	(1,109,916)	(1,005,970)
Total liabilities and stockholders' equity	$ 1,059,047	$ 1,369,726