Acquisitions and Divestitures Purchase Price Allocation (Details) (USD $) Share data in Millions, except Per Share data, unless otherwise specified	0 Months Ended	3 Months Ended	4 Months Ended	9 Months Ended
	Apr. 24, 2013	Jun. 30, 2013	Apr. 24, 2013	Sep. 30, 2014	Sep. 30, 2013	Dec. 31, 2013
Acquisitions and Divestitures [Abstract]
Business Acquisition, Total Consideration Transferred, Net of Proceeds From Investing Partners	$ 380,000,000
Business Acquisition, Purchase Price Adjustments, Effective Date to Date of Acquisition			19,000,000
Stock Issued During Period, Shares, Acquisitions	10
Stock Issued during period, Fair Value per Share, Acquisitions	$ 4.23		$ 4.23
Proceeds From Joint Interest Partners Upon Exercise of Preferential Rights Related to the Acquisition		21,000,000
BusinessAcquisition, Oil and Gas Properties - Proved	267,688,000		267,688,000	2,743,466,000		2,593,700,000
BusinessAcquisitionsPurchasePriceAllocationUnprovedOilandGasProperties	119,709,000		119,709,000
Business Acquisition, Purchase Price Allocation, Current Assets, Receivables	107,345,000		107,345,000
Business Acquisition, Purchase Price Allocation, Current Assets, Prepaid Expense and Other Assets	2,068,000		2,068,000
Business Acquisition, Purchase Price Allocation, Assets Acquired	496,810,000		496,810,000
Business Acquisition, Purchase Price Allocation, Current Liabilities, Accounts Payable	94,771,000		94,771,000
Business Acquisition, Purchase Price Allocation, Current Liabilities, Accrued Liabilities	1,500,000		1,500,000
Business Acquisition, Purchase Price Allocation, Liabilities Assumed	96,271,000		96,271,000
Business Acquisition, Purchase Price Allocation, Assets Acquired (Liabilities Assumed), Net	400,539,000		400,539,000
Cash Payments To Acquire Business, Net of Amounts Received for Preferential Rights	358,239,000			0	358,239,000
Stock Issued During Period, Value, Acquisitions	42,300,000
Business Combination, Consideration Transferred	$ 400,539,000