Consolidated Balance Sheets (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Current assets:
Cash and cash equivalents	$ 18,593	$ 974
Accounts receivable (less allowance for doubtful accounts of $5,342 and $5,343 at December 31, 2013 and 2012, respectively)	139,788	146,046
Materials and supplies	10,998	8,563
Current derivative asset (Note 13)	515	16,552
Current income tax receivable	0	901
Current deferred tax asset (Note 8)	13,585	8,765
Assets held for sale (Note 3)	15,621	0
Prepaid expenses and other	12,931	13,843
Total current assets	212,031	195,644
Oil and natural gas properties, on the full cost method:
Proved properties	4,235,712	3,822,381
Unproved properties not being amortized	545,588	521,659
Drilling equipment	1,477,093	1,478,645
Gas gathering and processing equipment	549,422	461,629
Transportation equipment	39,666	37,728
Other	87,435	62,840
Property, plant and equipment, gross, total	6,934,916	6,384,882
Less accumulated depreciation, depletion, amortization, and impairment	3,212,225	2,907,660
Net property and equipment	3,722,691	3,477,222
Debt issuance cost	11,844	13,432
Goodwill (Note 2)	62,808	62,808
Other intangible assets, net	0	680
Other assets	13,016	11,334
Total assets	4,022,390	3,761,120
Current liabilities:
Accounts payable	154,062	138,811
Accrued liabilities (Note 5)	64,363	54,098
Income taxes payable	7,474	0
Current derivative liabilities (Note 13)	5,561	1,948
Current portion of other long-term liabilities (Note 6)	12,113	12,282
Total current liabilities	243,573	207,139
Long-term debt (Note 6)	645,696	716,359
Non-current derivative liabilities (Note 13)	0	562
Other long-term liabilities (Note 6)	158,331	166,983
Deferred income taxes (Note 8)	801,398	695,776
Commitments and contingencies (Note 16)	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, 49,107,004 and 48,581,948 shares issued as of December 31, 2013 and 2012, respectively	9,659	9,594
Capital in excess of par value	445,470	423,603
Accumulated other comprehensive income (net of tax of $0 and $4,892, respectively) (Note 15)	0	7,587
Retained earnings	1,718,263	1,533,517
Total shareholders' equity	2,173,392	1,974,301
Total liabilities and shareholders' equity	$ 4,022,390	$ 3,761,120