Property And Equipment, Net (Narrative) (Details) (USD $)	0 Months Ended	1 Months Ended	3 Months Ended			12 Months Ended				3 Months Ended	6 Months Ended	3 Months Ended		1 Months Ended
	Sep. 28, 2011	May 31, 2011	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Jun. 30, 2011 ACP II [Member]	Dec. 31, 2010 ACP II [Member]	Jun. 30, 2011 Reliance [Member]	Oct. 31, 2012 Utica [Member] Avista Joint Venture [Member]	Oct. 31, 2012 Niobrara Formation - OIL India Ltd And Indian Oil Corporation Ltd [Member]	Oct. 31, 2012 Niobrara Formation - Haimo Oil And Gas LLC [Member]	Oct. 31, 2012 Carrizo [Member]
Property, Plant and Equipment [Line Items]
Costs not subject to amortization			$ 323,688,000			$ 323,688,000	$ 394,429,000
Capitalized costs of unproved properties						177,000,000	110,000,000	34,700,000	2,000,000
Net proceeds from sale of properties		98,000,000
Proceeds from sale of properties		104,000,000
Sale price of oil and gas property and equipment				19,300,000	190,000,000
Proceeds from sale of property			51,700,000	17,600,000	187,400,000	341,597,000	167,265,000	54,217,000						41,250,000	27,500,000
Joint venture investment, net proceeds ownership percentage													50.00%
Joint venture investment, original ownership percentage													10.00%
Proceeds of cash distributions recognized as reductions of capitalized oil and gas property costs	63,700,000									3,300,000	38,800,000
Cash received from Reliance due to exchange substitute properties												300,000
Percentage of ownership interest sold to related party												20.00%
Percentage of ownership interests sold	20.00%
Maximum future development costs receivable	$ 31,300,000													$ 41,250,000
Joint venture investment, ownership percentage														30.00%	10.00%	60.00%
Future development costs payment percentage	50.00%													50.00%