Condensed Consolidated Balance Sheets (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Current assets:
Cash and cash equivalents	$ 864	$ 1,049
Accounts receivable, net of allowance for doubtful accounts of $4,008 and $5,039 at March 31, 2015 and at December 31, 2014, respectively	134,093	189,812
Materials and supplies	7,977	5,590
Current derivative asset (Note 10)	26,713	31,139
Current deferred tax asset	11,527	11,527
Prepaid expenses and other	9,466	13,374
Total current assets	190,640	252,491
Oil and natural gas properties on the full cost method:
Proved properties	5,089,874	4,990,753
Unproved properties not being amortized	465,142	485,568
Drilling equipment	1,659,103	1,620,692
Gas gathering and processing equipment	634,114	628,689
Saltwater disposal systems	59,818	56,702
Transportation equipment	41,495	40,693
Other	66,864	57,706
Property, plant, and equipment, gross	8,016,410	7,880,803
Less accumulated depreciation, depletion, amortization, and impairment	4,243,886	3,747,412
Net property and equipment	3,772,524	4,133,391
Debt issuance cost	9,858	10,255
Goodwill	62,808	62,808
Other assets	15,075	14,783
Total assets	4,050,905	4,473,728
Current liabilities:
Accounts payable	131,911	218,500
Accrued liabilities (Note 5)	58,767	70,171
Income taxes payable	382	481
Current portion of other long-term liabilities (Note 6)	15,949	15,019
Total current liabilities	207,009	304,171
Long-term debt (Note 6)	883,584	812,163
Other long-term liabilities (Note 6)	142,597	148,785
Deferred income taxes	725,572	876,215
Shareholders' equity:
Preferred stock, $1.00 par value, 5,000,000 shares authorized, none issued	0	0
Common stock, $.20 par value, 175,000,000 shares authorized, 50,400,824 and 49,593,812 shares issued as of March 31, 2015 and December 31, 2014, respectively	9,827	9,732
Capital in excess of par value	476,131	468,123
Retained earnings	1,606,185	1,854,539
Total shareholders' equity	2,092,143	2,332,394
Total liabilities and shareholders' equity	$ 4,050,905	$ 4,473,728