Components of Selected Balance Sheet Accounts (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
Condensed Financial Statements, Captions [Line Items]
Asset Impairment Charges	$ 0	$ 6,084	$ 1,084	$ 123,992
Other current assets:
Tubular inventory and well materials	2,925		2,925		$ 5,802
Prepaid expenses	3,614		3,614		4,215
Other Assets, Miscellaneous, Current	763		763		97
Other Assets, Current	7,302		7,302		10,114
Other assets:
Assets of supplemental employee retirement plan (“SERP”)	4,014		4,014		4,123
Deferred issuance costs of the Revolver	1,796		1,796		1,623
Other	26		26		95
Other assets	5,836		5,836		5,841
Accounts payable and accrued liabilities:
Trade accounts payable	24,768		24,768		122,994
Drilling and other lease operating costs	26,643		26,643		68,842
Royalties and revenue – related	52,062		52,062		78,359
Compensation – related	12,853		12,853		9,197
Interest	37,438		37,438		15,555
Preferred stock dividends	0		0		6,067
Other	8,144		8,144		11,213
Accounts payable and accrued liabilities	161,908		161,908		312,227
Other liabilities:
Deferred gains on sale of assets	82,944		82,944		90,569
Firm transportation obligation	11,068		11,068		12,042
Asset retirement obligations	2,570		2,570		5,889
Defined benefit pension obligations	1,508		1,508		1,753
Postretirement health care benefit obligations	965		965		890
Compensation-related	1,150		1,150		7,631
Deferred compensation – SERP obligations and other	4,020		4,020		4,183
Other	1,012		1,012		929
Other liabilities	$ 105,237		$ 105,237		$ 123,886