Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Current assets:
Cash and cash equivalents	$ 839	$ 1,049
Accounts receivable, net of allowance for doubtful accounts of $4,008 and $5,039 at June 30, 2015 and at December 31, 2014, respectively	108,109	189,812
Materials and supplies	7,956	5,590
Current derivative asset (Note 10)	14,587	31,139
Current income taxes receivable	1,364	0
Current deferred tax asset	11,527	11,527
Assets held for sale (Note 3)	12,649	0
Prepaid expenses and other	9,503	13,374
Total current assets	166,534	252,491
Oil and natural gas properties on the full cost method:
Proved properties	5,173,365	4,990,753
Unproved properties not being amortized	460,963	485,568
Drilling equipment	1,667,614	1,620,692
Gas gathering and processing equipment	650,679	628,689
Saltwater disposal systems	60,239	56,702
Transportation equipment	40,568	40,693
Other	75,799	57,706
Property, plant, and equipment, gross	8,129,227	7,880,803
Less accumulated depreciation, depletion, amortization, and impairment	4,752,931	3,747,412
Net property and equipment	3,376,296	4,133,391
Debt issuance cost	9,461	10,255
Goodwill	62,808	62,808
Non-current derivative asset (Note 10)	137	0
Other assets	14,757	14,783
Total assets	3,629,993	4,473,728
Current liabilities:
Accounts payable	105,309	218,500
Accrued liabilities (Note 5)	55,700	70,171
Income taxes payable	0	481
Current portion of other long-term liabilities (Note 6)	16,891	15,019
Total current liabilities	177,900	304,171
Long-term debt (Note 6)	926,908	812,163
Other long-term liabilities (Note 6)	141,153	148,785
Deferred income taxes	560,432	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, 50,423,251 and 49,593,812 shares issued as of June 30, 2015 and December 31, 2014, respectively	9,831	9,732
Capital in excess of par value	481,973	468,123
Retained earnings	1,331,796	1,854,539
Total shareholders' equity	1,823,600	2,332,394
Total liabilities and shareholders' equity	$ 3,629,993	$ 4,473,728