Components of Selected Balance Sheet Accounts (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Other current assets:
Tubular inventory and well materials	$ 2,463	$ 4,033
Prepaid expenses	6,617	562
Prepaid Expense and Other Assets, Current, Total	9,080	4,595
Other assets:
Debt issuance costs	31,601	13,186
Assets of supplemental employee retirement plan (“SERP”)	3,364	3,237
Other	1,043	1,511
Other assets	36,008	17,934
Accounts payable and accrued liabilities:
Trade accounts payable	71,725	37,835
Drilling and other lease operating costs	50,808	37,703
Royalties	23,278	14,390
Production and franchise taxes	7,950	2,874
Compensation - related	4,782	6,853
Interest	17,098	5,828
Preferred stock dividends	1,725	1,687
Other	6,478	4,485
Accounts payable and accrued liabilities	183,844	111,655
Other liabilities:
Firm transportation obligation	13,806	14,333
Asset retirement obligations (“AROs”)	6,172	4,513
Defined benefit pension obligations	1,752	1,821
Postretirement health care benefit obligations	2,764	2,634
Deferred compensation - SERP obligation and other	3,441	3,310
Other	2,777	2,290
Other liabilities	$ 30,712	$ 28,901

Sum of the carrying values as of the balance sheet date of obligations incurred through that date and due within one year (or the operating cycle, if longer), including liabilities incurred (and for which invoices have typically been received) and payable to vendors for goods and services received, taxes, interest, rent and utilities, accrued salaries and bonuses, payroll taxes and fringe benefits.

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