Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Current assets:
Cash and cash equivalents	$ 893	$ 835
Accounts receivable (less allowance for doubtful accounts of $3,773 and $5,199 at December 31, 2016 and 2015, respectively)	83,954	79,941
Materials and supplies	3,340	3,565
Current derivative asset (Note 12)	0	10,186
Current income tax receivable	99	21,002
Current deferred tax asset (Note 8)	25,211	14,206
Assets held for sale	0	615
Prepaid expenses and other	7,699	9,908
Total current assets	121,196	140,258
Oil and natural gas properties, on the full cost method:
Proved properties	5,446,305	5,401,618
Unproved properties not being amortized	314,867	337,099
Drilling equipment	1,565,268	1,567,560
Gas gathering and processing equipment	705,859	689,063
Saltwater disposal systems	60,638	60,316
Corporate land and building	59,066	49,890
Transportation equipment	32,842	40,072
Other	48,590	45,489
Property, plant and equipment, gross, total	8,233,435	8,191,107
Less accumulated depreciation, depletion, amortization, and impairment	5,952,330	5,609,980
Net property and equipment	2,281,105	2,581,127
Goodwill (Note 2)	62,808	62,808
Non-current derivative asset (Note 12)	377	968
Other assets	13,817	14,681
Total assets	2,479,303	2,799,842
Current liabilities:
Accounts payable	88,793	87,413
Accrued liabilities (Note 5)	39,651	46,918
Current derivative liabilities (Note 12)	21,564	0
Current portion of other long-term liabilities (Note 6)	14,907	16,560
Total current liabilities	164,915	150,891
Long-term debt less unamortized discount and debt issuance costs (Note 6)	800,917	918,995
Non-current derivative liabilities (Note 12)	415	285
Other long-term liabilities (Note 6)	103,064	140,341
Deferred income taxes (Note 8)	215,922	275,750
Commitments and contingencies (Note 14)	0	0
Shareholders' equity:
Preferred stock, $1.00 par value, 5,000,000 shares authorized, none issued	0	0
Common stock, $0.20 par value, 175,000,000 shares authorized, 51,494,318 and 50,413,101 shares issued as of December 31, 2016 and 2015, respectively	10,016	9,831
Capital in excess of par value	502,500	486,571
Retained earnings	681,554	817,178
Total shareholders' equity	1,194,070	1,313,580
Total liabilities and shareholders' equity	$ 2,479,303	$ 2,799,842