Components of Selected Balance Sheet Accounts (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Other current assets:
Tubular inventory and well materials	$ 1,965	$ 2,271
Prepaid expenses	3,407	3,653
Prepaid Expense and Other Assets, Current, Total	5,372	5,924
Other assets:
Debt issuance costs	29,227	30,239
Assets of supplemental employee retirement plan (“SERP”)	3,815	3,734
Other	668	562
Other assets	33,710	34,535
Accounts payable and accrued liabilities:
Trade accounts payable	75,235	120,278
Drilling and other lease operating costs	62,620	51,529
Royalties	41,860	39,929
Production and franchise taxes	1,929	5,338
Compensation - related	7,951	8,584
Interest	37,833	15,718
Preferred stock dividends	1,722	1,725
Other	9,062	4,903
Accounts payable and accrued liabilities	238,212	248,004
Other liabilities:
Sale Leaseback Transaction Deferred Gain Noncurrent	10,095	0
Firm transportation obligation	12,964	13,245
Asset retirement obligations (“AROs”)	6,537	6,437
Defined benefit pension obligations	1,523	1,579
Postretirement health care benefit obligations	1,071	1,023
Deferred compensation - SERP obligations and other	4,089	3,883
Other	8,766	7,219
Other liabilities	$ 45,045	$ 33,386