Income Taxes (Details Textual) (USD $)	3 Months Ended			6 Months Ended	9 Months Ended	12 Months Ended
	Mar. 31, 2013	Dec. 31, 2012	Mar. 31, 2011	Jun. 30, 2012	Sep. 30, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Jun. 30, 2013
Operating Loss Carryforwards [Line Items]
Effective Income Tax Rate Reconciliation, Percent						17.70%
Income Tax Reconciliation, Change in Deferred Tax Assets Valuation Allowance						$ 8,885,000	$ (10,260,000)	$ 0
Effective Income Tax Rate Reconciliation, Change in State Deferred Tax Assets Valuation Allowance, Amount						1,345,000	0	0
Net capitalized costs less related deferred income taxes exceeded the full-cost ceiling	13,700,000		23,000,000	21,300,000	2,300,000		17,300,000
Impairment charge of net capitalized costs	21,200,000	26,700,000	35,700,000	33,200,000	3,600,000	21,229,000	63,475,000	35,673,000
Deferred income tax credit	7,500,000		12,700,000	11,900,000	1,300,000		9,400,000
Increase in valuation allowance							7,900,000
Valuation allowance against net deferred tax assets	15,800,000	10,300,000			2,400,000		10,300,000		6,700,000
Internal Revenue Service (IRS) [Member]
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards						171,300,000
State and Local Jurisdiction [Member]
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards						$ 3,100,000