Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Current assets:
Cash and cash equivalents	$ 913	$ 835
Accounts receivable, net of allowance for doubtful accounts of $5,174 and $5,199 at September 30, 2016 and December 31, 2015, respectively	71,955	79,941
Materials and supplies	3,334	3,565
Current derivative asset (Note 10)	0	10,186
Current income tax receivable	366	21,002
Current deferred tax asset	8,361	14,206
Assets held for sale	0	615
Prepaid expenses and other	8,717	9,908
Total current assets	93,646	140,258
Oil and natural gas properties on the full cost method:
Proved properties	5,434,782	5,401,618
Unproved properties not being amortized	322,992	337,099
Drilling equipment	1,568,053	1,567,560
Gas gathering and processing equipment	700,170	689,063
Saltwater disposal systems	60,554	60,316
Corporate land and building	58,767	49,890
Transportation equipment	33,168	40,072
Other	47,282	45,489
Property, plant, and equipment, gross	8,225,768	8,191,107
Less accumulated depreciation, depletion, amortization, and impairment	5,915,369	5,609,980
Net property and equipment	2,310,399	2,581,127
Goodwill	62,808	62,808
Non-current derivative asset (Note 10)	177	968
Other assets	14,161	14,681
Total assets	2,481,191	2,799,842
Current liabilities:
Accounts payable	56,375	87,413
Accrued liabilities (Note 5)	57,719	46,918
Current derivative liability (Note 10)	5,552	0
Current portion of other long-term liabilities (Note 6)	16,342	16,560
Total current liabilities	135,988	150,891
Long-term debt less debt issuance costs (Note 6)	854,583	918,995
Non-current derivative liability (Note 10)	265	285
Other long-term liabilities (Note 6)	103,657	140,341
Deferred income taxes	197,122	275,750
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, 51,496,833 and 50,413,101 shares issued as of September 30, 2016 and December 31, 2015, respectively	10,016	9,831
Capital in excess of par value	499,689	486,571
Retained earnings	679,871	817,178
Total shareholders' equity	1,189,576	1,313,580
Total liabilities and shareholders' equity	$ 2,481,191	$ 2,799,842