CONDENSED CONSOLIDATED BALANCE SHEETS (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013		Dec. 31, 2012
Current assets:
Cash and cash equivalents	$ 1,225		$ 1,056
Accounts receivable	81,879		67,516
Derivative instruments	10,094		40,190
Other current assets	16,864		16,318
Total current assets	110,062		125,080
Oil and natural gas properties, full cost method of accounting:
Proved, net of accumulated depletion of $8,284,724 and $8,237,186	1,229,752		1,459,312
Unproved	233,364		277,798
Net oil and natural gas properties	1,463,116		1,737,110
Other property and equipment, net of accumulated depreciation and amortization of $47,778 and $46,908	15,383		17,128
Net property and equipment	1,478,499		1,754,238
Deferred income taxes	4,150		14,681
Goodwill	239,420		239,420
Derivative instruments	3,780		8,335
Other assets	59,073		60,108
TOTAL ASSETS	1,894,984		2,201,862
Current liabilities:
Accounts payable and accrued liabilities	181,179		164,786
Accrued interest	23,803		23,407
Derivative instruments	15,772		9,347
Deferred income taxes	4,150		14,681
Current portion of long-term debt	12	[1]	12	[1]
Other current liabilities	12,927		14,092
Total current liabilities	237,843		226,325
Long-term debt	1,640,351		1,862,088
Asset retirement obligations	23,699		56,155
Derivative instruments	4,440		7,204
Other liabilities	93,402		92,914
Total liabilities	1,999,735		2,244,686
Shareholders’ equity:
Preferred stock, none issued and outstanding	0		0
Common stock, 119,330,398 and 118,245,320 shares issued and outstanding	11,933		11,825
Capital surplus	2,547,430		2,541,859
Accumulated deficit	(2,643,942)		(2,575,994)
Accumulated other comprehensive loss	(20,172)		(20,514)
Total shareholders’ equity (deficit)	(104,751)		(42,824)
TOTAL LIABILITIES AND SHAREHOLDERS' EQUITY	$ 1,894,984		$ 2,201,862

[1] Due in June 2013.