Components of Selected Balance Sheet Accounts (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014	Dec. 31, 2014
Condensed Financial Statements, Captions [Line Items]
Asset Impairment Charges	$ 1,084	$ 117,908	$ 1,084	$ 117,908
Other current assets:
Tubular inventory and well materials 1	4,452		4,452		$ 5,802
Prepaid expenses	3,825		3,825		4,215
Other Assets, Miscellaneous, Current	104		104		97
Other Assets, Current	8,381		8,381		10,114
Other assets:
Assets of supplemental employee retirement plan (“SERP”)	4,206		4,206		4,123
Deferred issuance costs of the Revolver	2,021		2,021		1,623
Other	95		95		95
Other assets	6,322		6,322		5,841
Accounts payable and accrued liabilities:
Trade accounts payable	84,584		84,584		174,496
Drilling and other lease operating costs	47,872		47,872		68,842
Royalties	26,263		26,263		27,883
Compensation – related	12,846		12,846		9,197
Interest	15,646		15,646		15,555
Preferred stock dividends	6,067		6,067		6,067
Other	4,611		4,611		10,187
Accounts payable and accrued liabilities	197,889		197,889		312,227
Other liabilities:
Deferred gains on sale of assets	91,226		91,226		90,569
Firm transportation obligation	11,390		11,390		12,042
Asset retirement obligations (“AROs”)	6,191		6,191		5,889
Defined benefit pension obligations	1,537		1,537		1,753
Postretirement health care benefit obligations	942		942		890
Compensation-related	1,124		1,124		7,631
Deferred compensation – SERP obligations and other	4,243		4,243		4,183
Other	929		929		929
Other liabilities	117,582		$ 117,582		$ 123,886
Tubular inventory and well materials
Condensed Financial Statements, Captions [Line Items]
Asset Impairment Charges	$ 1,100