Property and Equipment (Details 2) (USD $)	3 Months Ended		6 Months Ended						3 Months Ended			6 Months Ended			3 Months Ended	6 Months Ended			3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Dec. 31, 2012	Jun. 30, 2013 Maximum	Oct. 02, 2012 10.75% senior unsecured notes	May 31, 2013 9.25% senior unsecured notes	Jun. 30, 2013 Series A Preferred Stock	Mar. 31, 2013 Series A Preferred Stock	Jun. 30, 2013 Eagle Property Acquisition	Jun. 30, 2013 Eagle Property Acquisition	Oct. 02, 2012 Eagle Property Acquisition	Oct. 02, 2012 Eagle Property Acquisition 10.75% senior unsecured notes	Jun. 30, 2013 Anadarko Basin Acquisition	Jun. 30, 2013 Anadarko Basin Acquisition	May 31, 2013 Anadarko Basin Acquisition	May 31, 2013 Anadarko Basin Acquisition 9.25% senior unsecured notes Panther Energy Company, LLC and its partners	Jun. 30, 2013 Eagle Property Acquisition and Anadarko Basin Acquisition Unaudited pro forma	Jun. 30, 2012 Eagle Property Acquisition and Anadarko Basin Acquisition Unaudited pro forma	Jun. 30, 2013 Eagle Property Acquisition and Anadarko Basin Acquisition Unaudited pro forma	Jun. 30, 2012 Eagle Property Acquisition and Anadarko Basin Acquisition Unaudited pro forma	Apr. 02, 2013 Other Property Acquisitions Gulf Coast
Acquisition information
Ceiling limit of capitalized cost for determining impairment to oil and gas properties (as a percent)						1.00%
Maximum period from the acquisition date for finalizing fair value of certain assets acquired and liabilities assumed																1 year
Oil and gas properties
Proved properties	$ 2,277,758,000		$ 2,277,758,000		$ 1,522,723,000												$ 417,280,000
Unevaluated																	207,400,000
Total assets acquired																	624,680,000
Asset retirement obligations	22,617,000		22,617,000		15,245,000												6,296,000
Total liabilities assumed																	6,296,000
Net assets acquired																	618,384,000						3,400,000
Revenues	126,008,000	102,582,000	197,030,000	132,825,000							44,900,000	83,300,000			14,200,000	14,200,000
Unaudited Pro forma information
Revenues and other																			154,225,000	183,766,000	267,086,000	275,308,000
Net income (loss)																			9,949,000	(99,800,000)	(1,695,000)	(119,798,000)
Preferred stock dividends									(2,700,000)	(4,100,000)									(2,709,000)	(6,500,000)	(6,826,000)	(13,000,000)
NET INCOME (LOSS) ATTRIBUTABLE TO COMMON SHAREHOLDERS	629,000	(112,377,000)	(11,437,000)	(129,884,000)															7,240,000	(106,300,000)	(8,521,000)	(132,798,000)
Net loss per common share - basic (in dollars per share)																			$ 0.11	$ (1.75)	$ (0.13)	$ (2.45)
Net loss per common share - diluted (in dollars per share)																			$ 0.11	$ (1.75)	$ (0.13)	$ (2.45)
Additional disclosures
Aggregate principal amount borrowed							600,000,000	700,000,000					600,000,000	600,000,000				700,000,000
Interest rate (as a percent)							10.75%	9.25%						10.75%				9.25%
Purchase price, cash													$ 325,000,000					$ 618,000,000