CONDENSED CONSOLIDATED BALANCE SHEETS (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
ASSETS
Cash and cash equivalents	$ 5,926	$ 119,194
Accounts receivable (Note 2)	254,805	210,368
Refundable income taxes	3,364	5,581
Prepaid expenses and other	30,017	68,026
Derivative asset	37,873	55,813
Deferred income taxes	8,579	4,222
Total current assets	340,564	463,204
Land	1,845	1,548
Proved oil and gas properties	5,401,684	4,378,987
Less - accumulated depletion, depreciation, and amortization	(2,376,170)	(1,766,445)
Unproved oil and gas properties	175,287	120,966
Wells in progress	273,928	273,428
Materials inventory, at lower of cost or market	13,444	16,537
Oil and gas properties held for sale net of accumulated depletion, depreciation and amortization of $20,676 in 2012 and $10,714 in 2011	33,620	246
Other property and equipment, net of accumulated depreciation of $22,442 in 2012 and $23,985 in 2011	153,559	71,369
Total property and equipment, net	3,677,197	3,096,636
Derivative asset	16,466	31,062
Restricted cash	86,773	124,703
Other noncurrent assets	78,529	83,375
Total other noncurrent assets	181,768	239,140
Total Assets	4,199,529	3,798,980
LIABILITIES
Accounts payable and accrued expenses (note 2)	525,627	456,999
Derivative liabilities	8,999	42,806
Other current liabilities	6,920	6,000
Total current liabilities	541,546	505,805
Long-term credit facility	340,000	0
3.50% Senior Convertible Notes, net of unamortized discount of $2,431 in 2011	0	285,069
6.625% Senior Notes due 2019	350,000	350,000
6.50% Senior Notes due 2021	350,000	350,000
6.50% Senior Notes due 2023	400,000	0
Asset retirement obligation	112,912	87,167
Asset retirement obligation associated with oil and gas properties held for sale	1,393	1,277
Net Profits Plan liability	78,827	107,731
Deferred income taxes	537,383	568,263
Derivative liabilities	6,645	12,875
Other noncurrent liabilities	66,357	67,853
Total noncurrent liabilities	2,243,517	1,830,235
Commitments and Contingencies
STOCKHOLDERS' EQUITY
Common stock, $0.01 par value - authorized: 200,000,000 shares; issued: 66,245,816 shares in 2012 and 64,145,482 shares in 2011; outstanding, net of treasury shares: 66,195,235 shares in 2012 and 64,064,415 shares in 2011	662	641
Additional paid-in capital	233,642	216,966
Treasury stock, at cost: 50,581 shares in 2012 and 81,067 shares in 2011	(1,221)	(1,544)
Retained earnings	1,190,397	1,251,157
Accumulated other comprehensive loss	(9,014)	(4,280)
Total stockholders' equity	1,414,466	1,462,940
Total Liabilities and Stockholders' Equity	$ 4,199,529	$ 3,798,980