Components of Selected Balance Sheet Accounts (Detail) (USD $) In Thousands	Jun. 30, 2011	Dec. 31, 2010
Other current assets:
Tubular inventory and well materials	$ 2,256	$ 3,600
Prepaid expenses	1,648	633
Prepaid Expense and Other Assets, Current, Total	3,904	4,233
Other assets:
Debt issuance costs	16,749	14,300
Long-term investments - SERP	5,363	6,440
Other	46	47
Other assets	22,158	20,787
Accounts payable and accrued liabilities:
Trade accounts payable	34,493	33,831
Drilling costs	24,052	31,770
Royalties	10,413	9,308
Production and franchise taxes	4,593	6,012
Compensation	5,100	9,631
Interest	6,241	2,977
Other	4,432	6,132
Accounts payable and accrued liabilities	89,324	99,661
Other liabilities:
Asset retirement obligation	7,312	7,364
Pension	1,700	1,766
Postretirement health care	2,978	2,976
Deferred compensation	5,688	6,952
Other	900	900
Other liabilities	$ 18,578	$ 19,958