Consolidated Balance Sheets (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Current assets:
Cash and cash equivalents	$ 974	$ 835
Accounts receivable (less allowance for doubtful accounts of $5,343 both at December 31, 2012 and 2011)	146,046	165,276
Materials and supplies	8,563	8,202
Current derivative asset (Note 13)	16,552	31,938
Current income tax receivable	901	0
Current deferred tax asset (Note 8)	8,765	10,936
Prepaid expenses and other	13,843	11,278
Total current assets	195,644	228,465
Property and equipment:
Drilling equipment	1,478,645	1,423,570
Oil and natural gas properties, on the full cost method:
Proved properties	3,822,381	3,302,032
Undeveloped leasehold not being amortized	521,659	185,632
Gas gathering and processing equipment	461,629	278,919
Transportation equipment	37,728	34,118
Other	62,840	37,544
Property, plant and equipment, gross, total	6,384,882	5,261,815
Less accumulated depreciation, depletion, amortization and impairment	2,907,660	2,319,484
Net property and equipment	3,477,222	2,942,331
Debt issuance cost	13,432	5,671
Goodwill (Note 2)	62,808	62,808
Other intangible assets, net	680	1,855
Non-current derivative asset (Note 13)	0	4,514
Other assets	11,334	11,076
Total assets	3,761,120	3,256,720
Current liabilities:
Accounts payable	138,811	143,311
Accrued liabilities (Note 5)	53,162	51,733
Income taxes payable	0	781
Contract advances	936	2,055
Current derivative liabilities (Note 13)	1,948	2,657
Current portion of other long-term liabilities (Note 6)	12,282	12,213
Total current liabilities	207,139	212,750
Long-term debt (Note 6)	716,359	300,000
Non-current derivative liabilities (Note 13)	562	0
Other long-term liabilities (Note 6)	166,983	113,830
Deferred income taxes (Note 8)	695,776	683,123
Commitments and contingencies (Note 15)	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, 48,581,948 and 48,151,442 shares issued as of December 31, 2012 and 2011, respectively	9,594	9,541
Capital in excess of par value	423,603	408,109
Accumulated other comprehensive income (net of tax of $4,892 and $11,961, respectively)	7,587	19,026
Retained earnings	1,533,517	1,510,341
Total shareholders' equity	1,974,301	1,947,017
Total liabilities and shareholders' equity	$ 3,761,120	$ 3,256,720