Business Combinations And Other Acquisitions (Acquisition Of Oil And Gas Mineral Rights) (Narrative) (Details) (USD $)	12 Months Ended	3 Months Ended	6 Months Ended	12 Months Ended			0 Months Ended	1 Months Ended	3 Months Ended	6 Months Ended
	Dec. 31, 2011 Cana Woodford Region Of Oklahoma [Member]	Jun. 30, 2013 Utica Shale Region Of Ohio [Member] acre	Jun. 30, 2013 Utica Shale Region Of Ohio [Member] item acre	Dec. 31, 2012 Utica Shale Region Of Ohio [Member] item acre	Sep. 30, 2012 Utica Shale Region Of Ohio [Member] acre	Dec. 31, 2011 Utica Shale Region Of Ohio [Member] acre	Mar. 06, 2012 Utica Shale Region Of Ohio [Member] Lease Agreement [Member] acre	Apr. 30, 2013 Utica Shale Region Of Ohio [Member] Lease Agreement [Member]	Jun. 30, 2012 Utica Shale Region Of Ohio [Member] Lease Agreement [Member]	Jun. 30, 2013 Utica Shale Region Of Ohio [Member] Lease Agreement [Member]
Business Acquisition [Line Items]
Ownership percentage		5.00%	5.00%		5.00%	10.80%
Gross acreage		137,000	137,000		125,000	80,000
Net acreage		6,850	6,850		6,250		1,232
Cumulative investment in pro rata interest in oil and gas leases		$ 25,200,000	$ 25,200,000
Drilling costs			9,300,000	5,300,000
Number of wells that began production			11	2
Investment revenue		1,200,000	1,500,000
Lease term										5 years
Lease renewal term										3 years
Lease bonus per acre										6,000
Lease revenue							500,000		6,900,000	7,400,000
Royalty percentage										20.00%
Proceeds from the sale of royalty interest								10,500,000
Gain on sale of royalty interest								10,500,000
Acquisition of mineral rights	$ 8,100,000