Components of Selected Balance Sheet Accounts (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
Other current assets:
Tubular inventory and well materials	$ 4,973	$ 14,251
Prepaid expenses	610	699
Prepaid Expense and Other Assets, Current, Total	5,583	14,950
Other assets:
Debt issuance costs	13,759	16,993
Assets of supplemental employee retirement plan ("SERP")	3,200	3,088
Other	1,888	51
Other assets	18,847	20,132
Accounts payable and accrued liabilities:
Trade accounts payable	30,081	30,186
Drilling costs	31,826	30,948
Royalties	13,244	15,235
Production and franchise taxes	6,858	3,495
Compensation	5,531	5,186
Interest	19,155	5,964
Other	5,326	3,490
Accounts payable and accrued liabilities	112,021	94,504
Other liabilities:
Restructuring Reserve, Noncurrent	14,443	0
Asset retirement obligations	4,543	6,283
Defined benefit pension obligations	1,660	1,763
Postretirement health care benefit obligations	3,035	3,022
Deferred compensation - SERP obligation and other	3,300	3,172
Other	2,277	1,647
Other liabilities	$ 29,258	$ 15,887