Condensed Consolidating Financial Statements - Schedule of Condensed Consolidating Balance Sheet (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Current assets
Cash and cash equivalents	$ 9,730	$ 45,811	$ 91,901	$ 213,447
Accounts receivable — oil and gas revenues	96,495	130,934
Accounts receivable — joint interest and other	100,914	175,537
Accounts receivable – affiliates	0	0
Inventory	11,072	21,354
Prepaid expenses	7,328	14,273
Derivative instruments	139,697	302,159
Other current assets	50	6,539
Total current assets	365,286	696,607
Property, plant and equipment
Oil and gas properties (successful efforts method)	6,284,401	5,966,140
Other property and equipment	443,265	313,439
Less: accumulated depreciation, depletion, amortization and impairment	(1,509,424)	(1,092,793)
Total property, plant and equipment, net	5,218,242	5,186,786
Assets held for sale	26,728	0
Investments in and advances to subsidiaries	0	0
Derivative instruments	15,776	13,348
Deferred income taxes	0	0
Other assets	23,343	12,335
Total assets	5,649,375	5,909,076	4,678,041
Current liabilities
Accounts payable	9,983	20,958
Accounts payable - affiliates	0	0
Revenues and production taxes payable	132,356	209,890
Accrued liabilities	167,669	410,379
Accrued interest payable	49,413	49,786
Deferred income taxes	0	97,499
Advances from joint interest partners	4,647	6,616
Other current liabilities	6,500	0
Total current liabilities	370,568	795,128
Long-term debt	2,302,584	2,670,664
Deferred income taxes	608,155	526,770
Asset retirement obligations	35,338	42,097
Liabilities held for sale	10,228	0
Other liabilities	3,160	2,116
Total liabilities	3,330,033	4,036,775
Stockholders’ equity
Capital contributions from affiliates	0	0
Common stock, $0.01 par value: 300,000,000 shares authorized; 139,583,990 shares issued and 139,076,064 shares outstanding at December 31, 2015 and 101,627,296 shares issued and 101,341,619 shares outstanding at December 31, 2014	1,376	1,001
Treasury stock, at cost: 507,926 shares and 285,677 shares at December 31, 2015 and 2014, respectively	(13,620)	(10,671)
Additional paid-in-capital	1,497,065	1,007,202
Retained earnings	834,521	874,769
Total stockholders’ equity	2,319,342	1,872,301	1,348,549	795,005
Total liabilities and stockholders’ equity	5,649,375	5,909,076
Parent/ Issuer
Current assets
Cash and cash equivalents	777	776	34,277	133,797
Accounts receivable — oil and gas revenues	0	0
Accounts receivable — joint interest and other	15	0
Accounts receivable – affiliates	1,248	781
Inventory	0	0
Prepaid expenses	278	297
Derivative instruments	0	0
Other current assets	0	0
Total current assets	2,318	1,854
Property, plant and equipment
Oil and gas properties (successful efforts method)	0	0
Other property and equipment	0	0
Less: accumulated depreciation, depletion, amortization and impairment	0	0
Total property, plant and equipment, net	0	0
Assets held for sale	0
Investments in and advances to subsidiaries	4,573,172	4,032,494
Derivative instruments	0	0
Deferred income taxes	205,174	149,317
Other assets	100	99
Total assets	4,780,764	4,183,764
Current liabilities
Accounts payable	0	0
Accounts payable - affiliates	247,488	91,459
Revenues and production taxes payable	0	0
Accrued liabilities	10	0
Accrued interest payable	49,340	49,340
Deferred income taxes		0
Advances from joint interest partners	0	0
Other current liabilities	0
Total current liabilities	296,838	140,799
Long-term debt	2,164,584	2,170,664
Deferred income taxes	0	0
Asset retirement obligations	0	0
Liabilities held for sale	0
Other liabilities	0	0
Total liabilities	2,461,422	2,311,463
Stockholders’ equity
Capital contributions from affiliates	0	0
Common stock, $0.01 par value: 300,000,000 shares authorized; 139,583,990 shares issued and 139,076,064 shares outstanding at December 31, 2015 and 101,627,296 shares issued and 101,341,619 shares outstanding at December 31, 2014	1,376	1,001
Treasury stock, at cost: 507,926 shares and 285,677 shares at December 31, 2015 and 2014, respectively	(13,620)	(10,671)
Additional paid-in-capital	1,497,065	1,007,202
Retained earnings	834,521	874,769
Total stockholders’ equity	2,319,342	1,872,301
Total liabilities and stockholders’ equity	4,780,764	4,183,764
Combined Guarantor Subsidiaries
Current assets
Cash and cash equivalents	8,953	45,035	57,624	79,650
Accounts receivable — oil and gas revenues	96,495	130,934
Accounts receivable — joint interest and other	100,899	175,537
Accounts receivable – affiliates	247,488	91,459
Inventory	11,072	21,354
Prepaid expenses	7,050	13,976
Derivative instruments	139,697	302,159
Other current assets	50	6,539
Total current assets	611,704	786,993
Property, plant and equipment
Oil and gas properties (successful efforts method)	6,284,401	5,966,140
Other property and equipment	443,265	313,439
Less: accumulated depreciation, depletion, amortization and impairment	(1,509,424)	(1,092,793)
Total property, plant and equipment, net	5,218,242	5,186,786
Assets held for sale	26,728
Investments in and advances to subsidiaries	0	0
Derivative instruments	15,776	13,348
Deferred income taxes	0	0
Other assets	23,243	12,236
Total assets	5,895,693	5,999,363
Current liabilities
Accounts payable	9,983	20,958
Accounts payable - affiliates	1,248	781
Revenues and production taxes payable	132,356	209,890
Accrued liabilities	167,659	410,379
Accrued interest payable	73	446
Deferred income taxes		97,499
Advances from joint interest partners	4,647	6,616
Other current liabilities	6,500
Total current liabilities	322,466	746,569
Long-term debt	138,000	500,000
Deferred income taxes	813,329	676,087
Asset retirement obligations	35,338	42,097
Liabilities held for sale	10,228
Other liabilities	3,160	2,116
Total liabilities	1,322,521	1,966,869
Stockholders’ equity
Capital contributions from affiliates	3,369,895	2,899,203
Common stock, $0.01 par value: 300,000,000 shares authorized; 139,583,990 shares issued and 139,076,064 shares outstanding at December 31, 2015 and 101,627,296 shares issued and 101,341,619 shares outstanding at December 31, 2014	0	0
Treasury stock, at cost: 507,926 shares and 285,677 shares at December 31, 2015 and 2014, respectively	0	0
Additional paid-in-capital	8,743	8,743
Retained earnings	1,194,534	1,124,548
Total stockholders’ equity	4,573,172	4,032,494
Total liabilities and stockholders’ equity	5,895,693	5,999,363
Intercompany Eliminations
Current assets
Cash and cash equivalents	0	0	$ 0	$ 0
Accounts receivable — oil and gas revenues	0	0
Accounts receivable — joint interest and other	0	0
Accounts receivable – affiliates	(248,736)	(92,240)
Inventory	0	0
Prepaid expenses	0	0
Derivative instruments	0	0
Other current assets	0	0
Total current assets	(248,736)	(92,240)
Property, plant and equipment
Oil and gas properties (successful efforts method)	0	0
Other property and equipment	0	0
Less: accumulated depreciation, depletion, amortization and impairment	0	0
Total property, plant and equipment, net	0	0
Assets held for sale	0
Investments in and advances to subsidiaries	(4,573,172)	(4,032,494)
Derivative instruments	0	0
Deferred income taxes	(205,174)	(149,317)
Other assets	0	0
Total assets	(5,027,082)	(4,274,051)
Current liabilities
Accounts payable	0	0
Accounts payable - affiliates	(248,736)	(92,240)
Revenues and production taxes payable	0	0
Accrued liabilities	0	0
Accrued interest payable	0	0
Deferred income taxes		0
Advances from joint interest partners	0	0
Other current liabilities	0
Total current liabilities	(248,736)	(92,240)
Long-term debt	0	0
Deferred income taxes	(205,174)	(149,317)
Asset retirement obligations	0	0
Liabilities held for sale	0
Other liabilities	0	0
Total liabilities	(453,910)	(241,557)
Stockholders’ equity
Capital contributions from affiliates	(3,369,895)	(2,899,203)
Common stock, $0.01 par value: 300,000,000 shares authorized; 139,583,990 shares issued and 139,076,064 shares outstanding at December 31, 2015 and 101,627,296 shares issued and 101,341,619 shares outstanding at December 31, 2014	0	0
Treasury stock, at cost: 507,926 shares and 285,677 shares at December 31, 2015 and 2014, respectively	0	0
Additional paid-in-capital	(8,743)	(8,743)
Retained earnings	(1,194,534)	(1,124,548)
Total stockholders’ equity	(4,573,172)	(4,032,494)
Total liabilities and stockholders’ equity	$ (5,027,082)	$ (4,274,051)