Components of Selected Balance Sheet Accounts (Detail) (USD $) In Thousands	Sep. 30, 2011	Dec. 31, 2010
Other current assets:
Tubular inventory and well materials	$ 3,969	$ 3,600
Prepaid expenses	237	633
Prepaid Expense and Other Assets, Current, Total	4,206	4,233
Other assets:
Debt issuance costs	17,660	14,300
Long-term investments - SERP	3,674	6,440
Other	49	47
Other assets	21,383	20,787
Accounts payable and accrued liabilities:
Trade accounts payable	25,202	33,831
Drilling costs	25,285	31,770
Royalties	13,140	9,308
Production and franchise taxes	5,146	6,012
Compensation	6,947	9,631
Interest	19,319	2,977
Other	3,264	6,132
Accounts payable and accrued liabilities	98,303	99,661
Other liabilities:
Asset retirement obligations	6,019	7,364
Pension	1,666	1,766
Postretirement health care	2,966	2,976
Deferred compensation	3,806	6,952
Other	1,200	900
Other liabilities	$ 15,657	$ 19,958