Acquisitions and Divestitures (Details Textuals) (Cedar Creek Anticline [Member], USD $)	0 Months Ended	3 Months Ended
	Mar. 27, 2013	Jun. 30, 2013	Jun. 30, 2013
Cedar Creek Anticline [Member]
Business Acquisition [Line Items]
Business Acquisition, Cost of Acquired Entity, Cash Paid	$ 1,000,000,000
Business Combination, Pro Forma Information, Revenue of Acquiree since Acquisition Date, Actual		88,700,000	92,700,000
Business Combination, Pro Forma Information, Earnings or Loss of Acquiree since Acquisition Date, Actual		$ 65,200,000	$ 67,900,000