Supplemental Condensed Consolidating Financial Information (Supplemental Condensed Consolidating Statement of Operations) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Oil and natural gas									$ 688,743	$ 422,529	$ 348,207
Other									4,295	1,104	120
Total Revenue	142,610	183,992	184,087	182,349	138,899	86,668	99,270	98,796	693,038	423,633	348,327
Lease operating									165,841	94,850	70,281
Transportation									3,568	615	779
Exploration expenditures and dry hole costs									26,555	18,799	14,268
Impairments									2,937	8,883	32,466
Depreciation, depletion and amortization									200,359	113,581	104,624
Accretion of liability for asset retirement obligations									28,299	15,565	15,942
General and administrative									28,137	23,208	18,741
Taxes, other than on earnings									11,490	13,007	14,365
Gain on sale of assets									(28,681)
Gain on sale of assets									(28,681)
Other									34,942	4,678	9,735
Total costs and expenses	122,077	143,178	98,535	109,657	86,235	67,379	68,071	71,501	473,447	293,186	281,201
Income from operations	20,533	40,814	85,552	72,692	52,664	19,289	31,199	27,295	219,591	130,447	67,126
Interest income									99	136	102
Interest expense									(52,368)	(28,568)	(17,548)
Loss on derivative instruments									(32,361)	(13,305)	(5,870)
Total other income (expense)									(84,630)	(41,737)	(25,693)
Income (loss) before provision for income taxes									134,961	88,710	41,433
Deferred income tax expense									(49,687)	(29,900)	(14,822)
Total provision for income taxes									(49,687)	(29,900)	(14,822)
Net income	(12,058)	(1,284)	69,579	29,037	24,153	(2,247)	35,401	1,503	85,274	58,810	26,611
Parent Company [Member]
Oil and natural gas									606,743	318,749	245,567
Other									689	15,152	15,007
Total Revenue									607,432	333,901	260,574
Lease operating									140,605	71,002	51,618
Transportation									3,548	611	766
Exploration expenditures and dry hole costs									22,265	18,790	14,045
Impairments									2,937	8,883	32,532
Depreciation, depletion and amortization									178,427	92,689	82,168
Accretion of liability for asset retirement obligations									23,196	10,551	9,013
General and administrative									28,137	22,845	18,281
Taxes, other than on earnings									1,084	1,162	(733)
Gain on sale of assets									(28,219)
Other									34,072	5,496	9,940
Total costs and expenses									406,052	232,029	217,630
Income from operations									201,380	101,872	42,944
Interest income									99	136	102
Interest expense									(52,368)	(28,568)	(17,548)
Loss on derivative instruments									(32,361)	(13,305)	(5,870)
Income (loss) from equity investments									11,506	18,945	15,532
Total other income (expense)									(73,124)	(22,792)	(10,161)
Income (loss) before provision for income taxes									128,256	79,080	32,783
Deferred income tax expense									(42,982)	(20,270)	(6,172)
Net income									85,274	58,810	26,611
Guarantor Subsidiaries [Member]
Oil and natural gas									82,000	103,780	102,640
Other									3,606	952	113
Total Revenue									85,606	104,732	102,753
Lease operating									25,236	23,848	18,663
Transportation									20	4	13
Exploration expenditures and dry hole costs									4,290	9	223
Impairments											(66)
Depreciation, depletion and amortization									21,932	20,892	22,456
Accretion of liability for asset retirement obligations									5,103	5,014	6,929
General and administrative										15,363	15,460
Taxes, other than on earnings									10,406	11,845	15,098
Gain on sale of assets									(462)
Other									870	(818)	(205)
Total costs and expenses									67,395	76,157	78,571
Income from operations									18,211	28,575	24,182
Income (loss) before provision for income taxes									18,211	28,575	24,182
Deferred income tax expense									(6,705)	(9,630)	(8,650)
Net income									11,506	18,945	15,532
Consolidation, Eliminations [Member]
Other										(15,000)	(15,000)
Total Revenue										(15,000)	(15,000)
General and administrative										(15,000)	(15,000)
Total costs and expenses										(15,000)	(15,000)
Income (loss) from equity investments									(11,506)	(18,945)	(15,532)
Total other income (expense)									(11,506)	(18,945)	(15,532)
Income (loss) before provision for income taxes									(11,506)	(18,945)	(15,532)
Net income									$ (11,506)	$ (18,945)	$ (15,532)