Consolidated balance sheets (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Current assets:
Cash and cash equivalents	$ 31,024	$ 33,224
Accounts receivable, net	88,943	83,424
Derivative financial instruments	1,173	4,644
Deferred income taxes	17,753	12,713
Other current assets	5,590	3,016
Current assets held for sale	499	416
Total current assets	144,982	137,437
Oil and natural gas properties, full cost method:
Proved properties	3,187,143	2,993,266
Unproved properties not being amortized	132,146	159,946
Pipeline and gas gathering assets	26,165	23,065
Other fixed assets	29,916	23,669
Gross property and equipment	3,375,370	3,199,946
Less accumulated depreciation, depletion, amortization and impairment	1,195,300	1,130,867
Property and equipment held for sale, net of accumulated depreciation	45,072	44,812
Net property and equipment	2,225,142	2,113,891
Deferred income taxes	43,613	49,916
Derivative financial instruments	1,601	2,058
Deferred loan costs, net	28,150	29,444
Investment in equity method investee	874	0
Other assets, net	1,074	1,078
Noncurrent assets held for sale	4,480	4,480
Total assets	2,449,916	2,338,304
Current liabilities:
Accounts payable	29,726	47,560
Undistributed revenue and royalties	34,289	31,988
Accrued capital expenditures	98,932	121,612
Accrued compensation and benefits	6,097	10,318
Derivative financial instruments	12,367	1,325
Accrued interest payable	22,502	26,106
Other current liabilities	19,856	17,263
Current liabilities held for sale	6,584	5,896
Total current liabilities	230,353	262,068
Long-term debt	1,351,706	1,216,760
Derivative financial instruments	6,555	3,260
Asset retirement obligations	14,438	13,610
Other noncurrent liabilities	2,481	2,333
Noncurrent liabilities held for sale	8,909	8,550
Total liabilities	1,614,442	1,506,581
Stockholders' equity:
Preferred stock, $0.01 par value, 50,000,000 shares authorized and zero issued at March 31, 2013 and December 31, 2012	0	0
Common stock, $0.01 par value, 450,000,000 shares authorized, and 129,331,967 and 128,298,559 issued, net of treasury, at March 31, 2013 and December 31, 2012, respectively	1,293	1,283
Additional paid-in capital	963,756	961,424
Accumulated deficit	(129,571)	(130,980)
Treasury stock, at cost, 7,609 common shares at March 31, 2013 and December 31, 2012	(4)	(4)
Total stockholders' equity	835,474	831,723
Total liabilities and stockholders' equity	$ 2,449,916	$ 2,338,304