Components of Selected Balance Sheet Accounts (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011
Other current assets:
Tubular inventory and well materials	$ 8,170	$ 14,251
Prepaid expenses	1,057	699
Prepaid Expense and Other Assets, Current, Total	9,227	14,950
Other assets:
Debt issuance costs	16,311	16,993
Assets of supplemental employee retirement plan ("SERP")	3,339	3,088
Other	49	51
Other assets	19,699	20,132
Accounts payable and accrued liabilities:
Trade accounts payable	41,162	30,186
Drilling costs	20,881	30,948
Royalties	15,035	15,235
Production and franchise taxes	2,695	3,495
Compensation	2,668	5,186
Interest	19,423	5,964
Other	1,909	3,490
Accounts payable and accrued liabilities	103,773	94,504
Other liabilities:
Asset retirement obligations	6,392	6,283
Defined benefit pension obligations	1,728	1,763
Postretirement health care benefit obligations	3,018	3,022
Deferred compensation - SERP obligation and other	3,413	3,172
Other	1,522	1,647
Other liabilities	$ 16,073	$ 15,887