Components of Selected Balance Sheet Accounts (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Other current assets:
Tubular inventory and well materials	$ 5,588	$ 14,251
Prepaid expenses	1,262	699
Prepaid Expense and Other Assets, Current, Total	6,850	14,950
Other assets:
Debt issuance costs	15,617	16,993
Assets of supplemental employee retirement plan ("SERP")	3,298	3,088
Other	1,890	51
Other assets	20,805	20,132
Accounts payable and accrued liabilities:
Trade accounts payable	37,040	30,186
Drilling costs	16,116	30,948
Royalties	11,977	15,235
Production and franchise taxes	5,881	3,495
Compensation	4,827	5,186
Interest	6,208	5,964
Other	2,173	3,490
Accounts payable and accrued liabilities	84,222	94,504
Other liabilities:
Asset retirement obligations	6,440	6,283
Defined benefit pension obligations	1,694	1,763
Postretirement health care benefit obligations	3,011	3,022
Deferred compensation - SERP obligation and other	3,416	3,172
Other	2,014	1,647
Other liabilities	$ 16,575	$ 15,887